HK1192061B - P-type doping layers for use with light emitting devices - Google Patents

Description

P-type doped layer for light emitting devices

Cross Reference to Related Applications

This application claims priority to U.S. patent application No. 13/248,821, filed on 29/9/2011, and is hereby incorporated by reference in its entirety.

Background

Lighting applications typically use incandescent or gas filled bulbs, which typically do not have a long operating life and therefore require frequent replacement. Gas-filled tubes, such as fluorescent or neon tubes, may have a long lifetime, but require high voltages to operate and are relatively expensive. Further, both incandescent lamps and gas-filled tubes consume a large amount of energy.

A Light Emitting Diode (LED) is a device that emits light when electrons and holes are combined in an active layer of the LED. LEDs typically include a chip of semiconductor material doped with impurities to create a p-n junction. Current flows from the p-side or anode to the n-side or cathode. Charge carriers-electrons and holes-flow from electrodes with different voltages into the p-n junction. When an electron encounters a hole, the electron and hole recombine in a process that can result in radiant emission energy (hv) in the form of one or more photons. Photons or light exit an LED and are used in many applications such as, for example, lighting applications and electronic applications.

LEDs are relatively inexpensive, operate at low voltages, and have a long operating life compared to incandescent or gas filled light bulbs. Furthermore, the consumption of LEDs is relatively low power and compact. These properties make LEDs particularly desirable and well suited for many applications.

Despite these advantages, there are limitations associated with such devices. These limitations include material limitations that can limit the efficiency of the LED, structural limitations that can limit the transmission of light generated by the LED out of the device, and manufacturing limitations that can result in high processing costs. Accordingly, there is a need for improved LEDs and methods for manufacturing LEDs.

Disclosure of Invention

One aspect of the present invention provides a light emitting device, such as a Light Emitting Diode (LED). In an embodiment, a light emitting diode includes: an n-type gallium nitride (GaN) layer doped with an n-type dopant; and an active layer adjacent to the n-type GaN layer. The active layer may have one or more V-pits. A p-type GaN layer is adjacent to the active layer, the p-type GaN layer doped with a p-type dopant. The p-type GaN layer includes a first portion and a second portion laterally bounded by the one or more V-pits. The first portion is disposed over the active layer. The second portion has a uniform concentration of p-type dopant.

In another embodiment, a Light Emitting Diode (LED) includes a silicon substrate and an n-GaN layer adjacent to the silicon substrate. An active layer is adjacent to the n-GaN layer, and an electron blocking layer is adjacent to the active layer. A p-GaN layer is adjacent to the electron blocking layer. The LED includes Mg and In at an interface between the electron blocking layer and the p-GaN layer.

In another embodiment, a light emitting device includes: a first layer having n-type gallium nitride (GaN); and a second layer adjacent to the first layer. The second layer includes an active material configured to generate light upon recombination of electrons and holes. The second layer further includes one or more V-pits. A third layer is adjacent to the second layer, the third layer comprising p-type GaN having a uniform distribution of p-type dopants across portions of the third layer extending into one or more V-pits.

In another embodiment, a Light Emitting Diode (LED) includes: a first layer having n-type gallium nitride (GaN); and a second layer adjacent to the first layer. The second layer includes an active material configured to generate light upon recombination of electrons and holes. The third layer is adjacent to the second layer. The third layer includes a p-type dopant, and a wetting material (wetting material) configured to enable the p-type dopant to be uniformly distributed in the third layer.

In another embodiment, a light emitting diode includes an n-type gallium nitride (GaN) layer, and an active layer adjacent to the n-type GaN layer. The active layer may have one or more V-pits. A p-type GaN layer is adjacent to the active layer. The p-type GaN layer includes a first portion and a second portion laterally bounded by the one or more V-pits. The first portion is disposed over the active layer. The second portion has at least about 1x10¹⁹cm^-3P-type dopant concentration of (a).

In another embodiment, a light emitting diode includes: a first layer having n-type gallium nitride (GaN) or p-type GaN; and an active layer. The active layer is adjacent to the first layer and may have one or more V-pits. The light emitting diode further includes a second layer having the n-type GaN or the p-type GaN not used in the first layer. In other words, each of the first and second layers has a different one of the n-type GaN or p-type GaN materials. The second layer includes a first portion and a second portion laterally bounded by the one or more V-pits. The first portion is located over the active layer. The second portion has a uniform concentration of p-type dopant.

In another embodiment, a light emitting device includes: a first layer having an n-type group III-V semiconductor or a p-type group III-V semiconductor; and an active layer. The active layer is adjacent to the first layer and may have one or more V-pits (V-pits). The light emitting diode further includes a second layer having the n-type group III-V semiconductor or the p-type group III-V semiconductor not used in the first layer. In other words, the first and second layers each have a different one of the n-type group III-V semiconductor or the p-type group III-V semiconductor. The second layer includes a first portion and a second portion, the second portion laterally bounded by the one or more V-pits, and the first portion disposed over the active layer. The second portion has a uniform concentration of p-type dopant.

Another aspect of the invention provides a method for forming a light emitting device, such as a light emitting diode. In an embodiment, a method for forming a light emitting diode includes delta doping (deltadoping) a wetting layer (wettinglayer) with a p-type dopant. The wetting layer is formed adjacent to the electron blocking layer, and the electron blocking layer is formed adjacent to the active layer. The active layer is formed adjacent to an n-type group III-V semiconductor layer, and the n-type group III-V semiconductor layer is formed adjacent to a substrate. In some embodiments, the wetting layer is in direct contact with the electron blocking layer. In some embodiments, the electron blocking layer is in direct contact with the active layer. In some embodiments, the active layer is in direct contact with the n-type group III-V semiconductor layer.

In another embodiment, a method for forming a light emitting device, such as a light emitting diode, includes forming a p-type group III-V semiconductor layer adjacent to an active layer over a substrate in a reaction chamber (or reaction space if the reaction chamber includes a plurality of reaction spaces). The p-type group III-V semiconductor layer extends into one or more V-pits of the active layer. The p-type group III-V semiconductor layer is formed by delta doping the wetting layer with a p-type dopant and introducing a source gas of a group III species and a source gas of a group V species into the reaction chamber. In some cases, the wetting layer is formed adjacent to the active layer. In an example, the wetting layer is formed on the active layer.

Additional aspects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only exemplary embodiments of the present disclosure are shown and described. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

This specification incorporates by reference all publications, patents, and patent applications mentioned in this application to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

Drawings

A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:

FIG. 1 illustrates schematically a light emitting diode;

FIG. 2 illustrates a light emitting diode having a region of under-doped p-type gallium nitride (p-GaN) filled with V-defects of the source layer;

FIG. 3 illustrates a light emitting diode having a p-GaN layer adjacent to an active layer;

fig. 4 illustrates a light emitting device having a delta doped layer (deltadopedlayer) according to an embodiment;

FIG. 5 illustrates a light emitting device having a delta doped layer and other device layers according to an embodiment;

fig. 6 illustrates a method of forming a light emitting device according to an embodiment; and

FIG. 7 shows a graph of pressure versus time pulse for forming a Mg Δ doped layer and a p-GaN layer.

Detailed Description

While many embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will occur to those skilled in the art without departing from the invention herein. It should be understood that many alternatives to the embodiments of the invention described herein may be employed in practicing the invention.

The term "light emitting device" as used herein refers to a device configured to generate light when electrons and holes recombine in a light emitting region (or "active layer") of the device. In some examples, the light emitting device is a solid state device that converts electrical energy into light. The light emitting diode is a light emitting device. There are examples of LED device structures that are made of different materials, have different structures, and operate in many ways. Some LEDs emit laser light, while some generate non-monochromatic light. Some LEDs are optimized to perform a specific application. The LED may be a so-called blue LED comprising a Multiple Quantum Well (MQW) active layer with indium gallium nitride. The blue LED may emit non-monochromatic light having a wavelength ranging from about 440 nanometers to about 500 nanometers while having an average current density of 38 amperes per square centimeter or greater. A phosphor coating may be provided to absorb some of the blue light emitted. The phosphor then fluoresces to emit light at other wavelengths, so that the overall LED device emits light having a wider range of wavelengths.

The term "layer" as used herein is a layer of atoms or molecules on a substrate. In some examples, the layer comprises a single epitaxial layer or a plurality of epitaxial layers. A layer may comprise a film or film, or a plurality of films or films. In some cases, a layer is a structural component of a device (e.g., a light emitting device), providing a predetermined device function, such as, for example, an active layer configured to generate light. The thickness of a layer is typically from about one monoatomic Monolayer (ML) to tens, hundreds, thousands, millions, billions, trillions or more. In an example, the layer is a multi-layer structure having a thickness greater than one monoatomic monolayer. Further, the layer may comprise a plurality of material layers. In an example, the multiple quantum well active layer includes a plurality of well and barrier layers.

The term "active region" (or "active layer") as used herein refers to a light emitting region of a Light Emitting Diode (LED) configured to generate light. The active layer includes an active material that generates light when electrons and holes recombine, such as, for example, by means of an electrical potential applied across the active layer. The active layer may comprise one or more layers. In some examples, the active layer may include one or more barrier layers (or cladding layers, such as GaN) and quantum well ("well") layers (such as, for example, InGaN). In an example, the active layer includes multiple quantum wells, in which case the active layer may be referred to as a multiple quantum well ("MQW") active layer.

The term "doped" as used herein refers to a structure or layer that is doped with a dopant. The layers may be doped with n-type dopants (also referred to herein as "n-doping") or p-type dopants (also referred to herein as "p-doping"). In some examples, the layer is undoped or unintentionally doped (also referred to herein as "u-doped" or "u-type"). In an example, the u-GaN (or u-type GaN) layer includes undoped or unintentionally doped GaN.

The term "dopant" as used herein refers to a dopant, such as an n-type dopant or a p-type dopant. p-type dopants include, but are not limited to, magnesium, zinc, and carbon. n-type dopants include, but are not limited to, silicon and germanium. The p-type semiconductor is a semiconductor doped with a p-type dopant. An n-type semiconductor is a semiconductor doped with an n-type dopant. n-type group III-V semiconductors include group III-V semiconductors doped with an n-type, such as n-type gallium nitride ("n-GaN"). p-type group III-V semiconductors include group III-V semiconductors doped with a p-type, such as p-type gallium nitride ("p-GaN").

The term "adjacent" or "adjacent to" as used herein includes "adjacent", "adjoining", "contacting", and "immediately adjacent". In some examples, adjacent components are separated from one another by one or more intervening layers. For example, the thickness of the one or more intervening layers is less than about 10 micrometers ("micrometers"), 1 micrometer, 500 nanometers ("nm"), 100nm, 50nm, 10nm, 1nm, or less. In an example, the first layer is adjacent to the second layer when the first layer is in direct contact with the second layer. In other examples, the first layer is adjacent to the second layer when the first layer is separated from the second layer by a third layer.

The term "substrate" as used herein refers to any workpiece on which a film or film is to be formed. Substrates include, but are not limited to, silicon dioxide, sapphire, zinc oxide, carbon (e.g., graphite), SiC, AlN, GaN, spinel (spinel), coated silicon (coated silicon), silicon on oxide, silicon carbide on oxide, glass, gallium nitride, indium nitride, titanium dioxide, aluminum nitride, metallic materials (e.g., molybdenum, tungsten, copper, aluminum), and combinations (or alloys) of these.

The term "injection efficiency" as used herein refers to the ratio of electrons and holes injected into the active region of a light emitting device by the light emitting device.

The term "internal quantum efficiency" as used herein refers to the proportion of all electron-hole recombination that is radiated (i.e., generates photons) in the active region of the light emitting device.

The term "extraction efficiency" as used herein refers to the proportion of photons generated in the active region of a light emitting device that escape from the device.

As used herein, the term "external quantum efficiency" (EQE) refers to the ratio of the number of photons emitted from an LED to the number of electrons passing through the LED, i.e., EQE = injection efficiency x internal quantum efficiency x extraction efficiency.

An LED may be formed from a number of semiconductor device layers. In some cases, III-V semiconductor LEDs provide device parameters (e.g., light wavelength, external quantum efficiency) that are superior to other semiconductor materials. Gallium nitride (GaN) is a binary group III-V direct bandgap semiconductor that can be used in optoelectronic applications as well as high power and high frequency devices.

Group III-V semiconductor based LEDs may be formed on many substrates, such as silicon and sapphire. Silicon offers many advantages over other substrates, such as the ability to use current manufacturing and processing techniques in addition to using large size wafers to help maximize the number of LEDs formed in a particular time period. Fig. 1 shows an LED100 having a substrate 105, an AlGaN layer 110 adjacent to the substrate 105, a pit generation layer (pit generation layer)115 adjacent to the AlGaN layer 110, an n-type GaN ("n-GaN") layer 120 adjacent to the pit generation layer 115, an active layer 125 adjacent to the n-GaN layer 120, an electron blocking (e.g., AlGaN) layer 130 adjacent to the active layer 125, and a p-type GaN ("p-GaN") layer 135 adjacent to the electron blocking layer 130. The electron blocking layer 130 is configured to minimize recombination of electrons and holes in the p-GaN layer 135. The substrate 100 may be formed of silicon. In some examples, pit generation layer 115 includes unintentionally doped GaN ("u-GaN").

While silicon offers many advantages, such as the ability to use commercially available semiconductor fabrication techniques suitable for the use of silicon, the formation of III-V semiconductor-based LEDs on silicon substrates is still subject to many limitations. For example, lattice mismatch between silicon and gallium nitride and the coefficient of thermal expansion both result in structural stresses that generate defects such as line (threading) and/or hairpin (hairpin) dislocations (collectively referred to herein as "dislocations") upon formation of the gallium nitride film. The grown film around the defect creates a V-defect (or V-pit), i.e., a V-shaped or generally concave structure in the device layer. Such V-pits make it difficult to achieve consistent device characteristics, such as the distribution of dopants in one or more layers.

For example, p-type doping of GaN grown in V-defect pits (collectively referred to herein as "V pits") after formation of an aluminum gallium nitride (A1GaN) layer may not be sufficient to enable efficient hole emission from materials filled with V defects in the source region. This problem can be attributed to the tendency of p-type dopants (e.g., Mg) to segregate to the c-plane of the A1GaN surface opposite the cleaved V-defect AlGaN surface during film formation. The absorption of p-type dopants at the V-defect facet surface is relatively insensitive to the gas phase p-type dopant precursor concentration. Incorporation of p-type dopants occurs primarily along the c-plane surface. Fig. 2 shows an example of the resulting LED. The GaN material filling the pits is under-doped, resulting in poor device performance (e.g., low brightness, high power input) and/or inconsistent light output across the LED. That is, in instances where the doping profile of the p-type dopant in the p-type GaN (p-GaN) layer is not uniform, the electronic structure (or band diagram) of the LED may vary across the device, resulting in a non-uniform emission profile. In the illustrated example, the portion of the p-type layer in the V-defect is undoped, and thus lacks the concentration of p-type dopant (e.g., Mg) required for desired (or consistent) device performance. The portion of the p-type layer in the V-pit is under-doped with a p-type dopant concentration that is less than a concentration of p-type dopants in the p-GaN layer outside of the V-pit. In an example, the p-GaN layer in the V-pits has a p-type dopant concentration that is at most 1%, or 10%, or 20%, or 30%, or 40%, or 50%, or 60%, or 70%, or 80%, or 90% or 95% of the concentration of the p-type dopant in the p-GaN layer outside of the V-pits.

Ways to solve this problem include growing p-GaN with a low concentration of indium directly on the V-defect pit active region before AlGaN, thereby reducing the problem of p-type dopant (e.g., Mg) segregation on the A1GaN surface. Fig. 3 diagrammatically shows a light-emitting device having such a structure. While hole injection efficiency is achieved, at least some of the benefits obtained by having an intermediate electron blocking layer between the active layer and the p-GaN are lost.

Another way to solve this problem is to minimize the concentration of V-pits in the LED. For example, the active layer may be formed with a low or substantially low defect density, which helps to minimize coverage (or density) of the V-pits. However, this approach is not commercially feasible and/or is difficult to implement with current methods for forming LEDs. For example, the formation of LED component layers (e.g., active layers) with low defect density is a slow and resource consuming process, resulting in high process costs and device conversion rates that do not meet the commercial requirements of LED devices.

Device structures and methods are provided herein for reducing, if not eliminating, the problem of insufficient dopant concentration in the V-pits. The apparatus and methods provided herein advantageously eliminate the need to form LED component layers with low defect densities by compensating for the problem of poor and/or inconsistent dopant concentrations in many LED component layers.

The light emitting devices and methods described in many embodiments of the present invention solve the problem of p-type under-doping in the V-pits caused by the separation of p-type dopants into the c-plane of the AlGaN surface during the formation of the p-GaN layer. The methods and structures described herein provide high hole injection efficiency without the need for a p-type semiconductor layer below the A1GaN electron blocking layer (see fig. 3).

Light emitting device

In an aspect of the present invention, a light emitting device having an improved concentration of dopants in a V-pit is provided. Such a device structure minimizes or eliminates the need to form a light emitting device structure with the lowest defect density. By virtue of the structure provided herein, device structures having a relatively modest defect density (and thus V-pits) can be used, which advantageously reduces process costs.

In some embodiments, a light emitting device, such as a Light Emitting Diode (LED), includes a first layer of one of an n-type group III-V semiconductor layer and a p-type group III-V semiconductor layer, an active layer adjacent to the first layer, and a second layer of the other of the n-type group III-V semiconductor layer and the p-type group III-V semiconductor layer adjacent to the active layer. n-type group III-V semiconductors include group III-V semiconductors doped with an n-type dopant. p-type group III-V semiconductors include group III-V semiconductors doped with a p-type dopant. The active layer includes one or more V-pits. The second layer has a first portion and a second portion laterally bounded by the one or more V-pits. The first portion is disposed over the active layer. The second portion has a uniform concentration of n-type or p-type dopant. In an example, the III-V semiconductor material is gallium nitride. In certain embodiments, the active layer has a thickness of between about 1x10⁸cm^-2And 5x10⁹cm^-2Defect density in between. In other embodiments, the active layer has a thickness of between about 1x10⁹cm^-2And 2x10⁹cm^-2Defect density betweenAnd (4) degree.

Group III-V semiconductors include group III materials and group V materials. In certain embodiments, the group III species is gallium and the group V species is nitrogen. In certain embodiments, the group III species include gallium and/or indium. In other embodiments, the group III species include gallium, indium, and/or aluminum.

In some embodiments, a light emitting device includes an n-type gallium nitride (GaN) layer with an n-type dopant. The n-GaN layer is disposed adjacent to the active layer having one or more V-pits. That is, the formed active layer exhibits one or more V-shaped pits (or defects). The active layer is adjacent to a p-type GaN layer having a p-type dopant. The p-GaN layer has a first portion and a second portion. The second portion is laterally bounded by one or more V-pits. The first portion is disposed over the active layer and is not laterally bounded by one or more V-pits. In embodiments, the light emitting device is an initial light emitting device, requiring additional processes and/or device structures to complete.

In some examples, the p-GaN layer has a thickness ranging between about 10 nanometers ("nm") and 1000 nm. In other embodiments, the p-GaN layer has a thickness ranging between about 50nm and 500 nm. The thickness of the p-GaN layer is selected such that a light emitting device having predetermined operating conditions is provided.

In some examples, the n-GaN layer has a thickness ranging between about 100nm and 8 microns ("microns"), while in other embodiments the n-GaN layer has a thickness ranging between about 500nm and 6 microns. While in other embodiments the thickness of the n-GaN layer ranges between about 1 and 4 microns. The thickness of the n-GaN layer is selected such that a light emitting device having predetermined operating conditions is provided.

In particular embodiments, the p-type dopant includes one or more of magnesium, carbon, and zinc. In a particular implementation, the p-type dopant is magnesium.

In an embodiment, the n-type dopant includes one or more of silicon and germanium. In a particular implementation, the n-type dopant is silicon.

In some cases, the p-GaN layer further includes a wetting material to aid in doping of the p-GaN layer. In some examples, the wetting material may be used to uniformly distribute the p-type dopant across the layer of wetting material prior to forming the p-GaN layer (see below). In some cases, the wetting material is indium (In).

In some embodiments, the second portion has a uniform concentration of p-type dopant. In some examples, the concentration of the p-type dopant in the second portion is close to or substantially equal to the concentration of the p-type dopant (or another p-type dopant) in the first portion of the p-GaN layer. In an embodiment, the concentration of the p-type dopant in the second portion is about 90%, or 80%, or 70%, or 60%, or 50%, or 40%, or 30%, or 20%, or 10%, or 5%, or 1%, or 0.1%, or 0.01%, or 0.001% of the concentration of the p-type dopant in the first portion.

In an embodiment, the second portion is substantially doped with a p-type dopant. The concentration of the p-type dopant in the first portion and the second portion is between about 1x10¹⁸cm^-3And 1x10²²cm^-3In the meantime. In other embodiments, the concentration of the p-type dopant in the first portion and the second portion is between about 1x10¹⁹cm^-3And 1x10²¹cm^-3And in other embodiments, the concentration of the p-type dopant in the first portion and the second portion is between about 1x10²⁰cm^-3And 5x10²⁰cm^-3In the meantime.

In other cases, the concentration of the p-type dopant in the first portion is highest at or near the active layer and decreases toward the second portion. In other cases, the concentration of the p-type dopant in the first portion is uniform or substantially uniform along a direction parallel to the surface between the p-GaN layer and the active layer (also referred to herein as a "lateral axis"), and along a direction perpendicular to the surface between the p-GaN layer and the active layer (also referred to herein as a "longitudinal axis").

In a particular implementation, the concentration of the p-type dopant in the second portion is uniform along the vee pit longitudinal dimension. In some embodiments, the concentration of the p-type dopant in the V-pit, as measured along the longitudinal axis of the light emitting device, varies by up to about 50%, or 40%, or 30%, or 20%, or 10%, or 5%, or 1%, or 0.1%, or 0.01%, or 0.001%, or 0.0001%. In other examples, the concentration of the p-type dopant in the second portion is uniform along the lateral dimension of the V-pits. In some embodiments, the concentration of the p-type dopant in the V-pit, as measured along the lateral axis of the light emitting device, varies by at most about 50%, or 40%, or 30%, or 20%, or 10%, or 5%, or 1%, or 0.1%, or 0.01%, or 0.001%, or 0.0001%.

The light emitting device further includes a substrate adjacent to the n-type or p-type GaN layer. In an example, the substrate comprises silicon, such as, for example, n-type silicon, or sapphire. In some examples, the substrate is used in a finished light emitting device. In other examples, the substrate is a carrier substrate, and in such examples, the completed light emitting device will include another substrate. In certain embodiments, the substrate has a thickness ranging between about 200 micrometers (μm) and 2 millimeters (mm).

In some embodiments, the light emitting device includes a pit generation layer. In some examples, the pit generation layer is adjacent to the n-type GaN layer, such as below the n-type GaN layer and the active layer. In other examples, the pit generation layer is interposed between the n-type GaN layer and the active layer. The pit generation layer facilitates growth of one or more V-pits during formation of the active layer, and in some instances other layers formed over the active layer.

In some embodiments, the pit generation layer has a thickness of between about 1x10⁸cm^-2And 5x10⁹cm^-2Between defect densities, while in other embodiments the pit generation layer has a defect density of between about 1x10⁹cm^-2And 2x10⁹cm^-2Defect density in between. In some embodiments, the pit generation layer has a thickness between about 10nm and 1000nm, while in other embodiments, the pit generation layer has a thickness between about 50nm and 500 nm.

The light emitting device includes an electrode in electrical communication with the n-GaN layer, either by being in direct contact with the n-GaN layer or by one or more intervening layers. The light emitting device further includes an electrode in electrical communication with (or electrically coupled to) the p-GaN layer, either by being in direct contact with the p-GaN layer or by one or more intervening layers. In some examples, one or both of the electrodes have a shape and configuration (e.g., location on the light-emitting device) selected to minimize obstruction of light emitted from the light-emitting device.

The active layer may be a quantum well active layer, such as a Multiple Quantum Well (MQW) active layer. In an embodiment, the active layer includes a well layer formed of indium gallium nitride and/or indium aluminum gallium nitride. The material including the active layer may be compositionally graded (also referred to as "grading" in this specification) with two or more elements including the active layer. In an example, the active layer is composed of graded indium gallium nitride In_xGa_1-xN, where "x" is a number between 0 and 1, and the barrier (or cladding) layer is formed of GaN. The composition of such a layer may vary from the first side to the second side of the layer. In some embodiments, the well or barrier material is selected from among gallium nitride, many compositions (or stoichiometries) of InAlGaN, and many compositions of AlGaN. In some embodiments, the active layer has a thickness between about 10nm and 1000nm, while in other embodiments, the active layer has a thickness between about 50nm and 200 nm.

In some embodiments, the active layer has between about 1x10⁸cm^-2And 5x10⁹cm^-2Between defect densities, while in other embodiments the active layer has a defect density of between about 1x10⁹cm^-2And 2x10⁹cm^-2Defect density in between. In some embodiments, the active layer has greater than about 1x10⁶cm^-2Greater than about 1x10⁷cm^-2Greater than about 1x10⁸cm^-2Or greater than about 1x10⁹cm^-2The defect density of (2).

In some embodiments, the thickness of the light emitting device between the n-GaN layer and the p-GaN layer is less than about 4 microns, less than about 3 microns, less than about 2 microns, less than about 1 micron, or less than about 500 nm. The region between the n-GaN layer and the p-GaN layer includes an active layer.

In some examples, the light emitting device includes an electron blocking layer between the active layer and the p-GaN layer. The electron blocking layer is configured to minimize recombination of electrons and holes in the p-GaN layer, which is undesirable when light emission in the active layer is desired. In an example, the electron blocking layer is formed of aluminum gallium nitride or aluminum indium gallium nitride. The electron blocking layer may be compositionally graded (also referred to as "grading" in this specification) with two or more elements of the electron blocking layer. For example, the electron blocking layer may be made of graded aluminum gallium nitride (AlGaN) Al_xGa_1-xN, where "x" is a number between 0 and 1, or from Al_xIn_yGa_1-x-yN, where "x" and "y" are numbers between 0 and 1. The composition of such a layer may vary from the first side to the second side of the layer. In certain embodiments, the electron blocking layer has a thickness between about 1nm and 1000nm or between about 10nm and 100 nm.

In some embodiments, the light emitting device further includes a p-type dopant injection layer between the active layer and the p-GaN layer. The p-type dopant injection layer is configured to provide p-type dopants to the second portion of the p-GaN layer during the formation of the p-GaN layer. The p-type dopant implant layer advantageously helps to provide a desired or predetermined p-type dopant concentration in the V-pits, which helps to minimize, if not eliminate, problems with under-doped regions of the p-GaN layer. The p-type dopant implant layer includes a p-type dopant and, in some examples, a wetting material. In some embodiments, the p-type dopant is magnesium (Mg). In some embodiments, the wetting material is indium (In). The wetting material is configured to enable the p-type dopant to uniformly cover the p-type dopant implant layer. In some examples, the wetting material may remain at the interface between the p-GaN layer and the electron blocking layer or active layer (when the electron blocking layer has been eliminated).

In some embodiments, the p-type dopant implant layer has a thickness of less than about 100nm, or less than about 50nm, or less than about 10nm, or less than about 1nm, or less. In some examples, the thickness of the p-type dopant implant layer is described as a single atomic Monolayer (ML). In some embodiments, the thickness of the p-type dopant implantation layer is between about 0.1ML and 10 ML. In other embodiments, the p-type dopant implantation layer has a thickness of less than or equal to about 10ML, or less than or equal to about 5ML, or less than or equal to about 4ML, or less than or equal to about 3ML, or less than or equal to about 2ML, or less than or equal to about 1ML, or less than or equal to about 0.5ML, or less.

In some embodiments, a Light Emitting Diode (LED) includes an n-type gallium nitride (GaN) layer, an active layer adjacent to the n-type GaN layer, and a p-type GaN layer adjacent to the active layer. The active layer includes one or more V-pits. The p-type GaN layer includes a first portion and a second portion. The second portion is laterally bounded by one or more V-pits. The first portion is disposed over the active layer and has at least about 1x10¹⁸cm^-3Or at least about 1x10¹⁹cm^-3Or at least about 1x10²⁰cm^-3Or at least about 1x10²¹cm^-3Or at least about 1x10²²cm^-3P-type dopant concentration of (a). In some examples, the concentration of the p-type dopant is between about 1x10¹⁸cm^-3And 1x10²²cm^-3Between, or between about 1x10¹⁹cm^-3And 1x10²¹cm^-3Between, or between about 1x10²⁰cm^-3And 5x10²⁰cm^-3In the meantime.

In some embodiments, a Light Emitting Diode (LED) includes a first layer of one of n-type gallium nitride (GaN) and p-type GaN, and an active layer adjacent to the first layer, the active layer having one or more V-pits. The LED further includes a second layer of the other of n-type gallium nitride (GaN) and p-type GaN, the second layer having a first portion and a second portion laterally bounded by one or more V-pits. The first portion is disposed over the active layer. The second portion has a uniform concentration of n-type or p-type dopant.

Fig. 4 illustrates a light emitting device ("device") 400 according to an embodiment of the present invention. In an example, the light emitting device 400 is a light emitting diode. Light emitting device 400 includes, from bottom to top, an n-doped (or "n-type") GaN layer ("n-GaN layer") 405, a pit generation layer 410 adjacent to n-GaN layer 405, an active layer 415 adjacent to pit generation layer 410, an electron blocking layer 420 adjacent to active layer 415, a p-type dopant injection layer 425 adjacent to electron blocking layer 420, and a p-GaN layer 430 adjacent to p-type dopant injection layer 425. Apparatus 400 includes a plurality of V-pits 435 (two shown) formed by defects (e.g., dislocations) in layer-by-layer material layers, pit generation layer 410, active layer 415, and electron blocking layer 420. The p-GaN layer 430 includes a first portion 430a and a second portion 430b, the second portion 430b being disposed in the V-pit 435. The p-type dopant implant layer includes a p-type dopant and, in some instances, a wetting material. The p-type dopant implant layer helps form the second portion 430b with a desired (or predetermined) uniformity, distribution, and/or concentration of p-type dopants in the second portion 430 b.

In some embodiments, active layer 415 is a multiple quantum well active layer. In an embodiment, the active layer is formed by alternating layers of well layers and barrier layers, implanted with alternating layers of indium gallium nitride and gallium nitride, or alternating layers of indium aluminum gallium nitride and gallium nitride. Gallium nitride in both examples may be used as the barrier layer material. Indium gallium nitride or indium aluminum gallium nitride may be used as the well layer material.

In an example, the active layer 415 is formed of alternating aluminum gallium nitride layers and gallium nitride layers, the electron blocking layer 420 is formed of aluminum gallium nitride, and the p-type dopant injection layer 425 is formed of magnesium and indium. In this example, indium is used as the wetting material. Alternatively, the electron blocking layer 420 is formed of a quaternary material, implanted with aluminum indium gallium nitride. In some examples, the electron blocking layer 420 is graded according to composition. In other examples, the electron blocking layer 420 has a uniform composition (composition).

The device 400 is formed on a substrate (not shown). The substrate is disposed adjacent to the n-GaN layer 405 or the p-GaN layer 430. In an embodiment, the substrate is formed of silicon or sapphire. In some examples, the substrate is disposed adjacent to the n-GaN layer 405, and a buffer layer having an AlN layer and an AlGaN layer is formed between the substrate and the n-GaN layer 405. The AlN layer is disposed adjacent to the substrate, and the AlGaN layer is disposed adjacent to the AlN layer and the n-GaN layer 405.

In implementation, the substrate disposed adjacent to the n-GaN layer 405 is formed of silicon. The substrate may be used to transfer the layers 405-430 to another substrate, such as silicon. In this example, layers 405-430 are formed on a first substrate disposed adjacent to the n-GaN layer, and after transfer, layers 405-430 are disposed on a second substrate adjacent to the p-GaN layer.

Figure 5 illustrates a device 500 having a plurality of layers 510 and 535 formed on a substrate 505 in accordance with an embodiment of the present invention. The device 500 is a light emitting device, such as a light emitting diode. Device 500 includes, from bottom to top ("bottom" representing a position adjacent to substrate 505), an n-GaN layer 510, a pit generation layer 515, an active layer 520, an electron blocking layer 525, a delta doped layer (deltadopedlayer)530, and a p-GaN layer 535. The p-GaN layer 535 includes a first portion and a second portion (not shown). The second portion is formed in one or more V-pits in pit generation layer 515, active layer 520, and electron blocking layer 525 (see, e.g., fig. 4). Delta doped layer 530 includes a p-type dopant, such as magnesium, and a wetting material, such as indium. In some cases, the wetting material reduces the barrier to p-type dopant migration on the surface of the delta-doped layer, enabling the p-type material to consistently cover the delta-doped layer. The wetting material may reduce the surface energy of the p-type dopant (e.g., Mg) on the V-defect. As described below, p-type dopant is provided into delta doped layer 530 by pulsing a source gas for the p-type dopant into the chamber having substrate 505.

In an example, delta doped layer 530 includes a wetting material, such as indium, that reduces the surface energy of the p-type dopant (e.g., Mg) in the V-defect facets, thereby helping to incorporate the p-type dopant into the wetting layer. The p-type dopant in delta doped layer 530 provides a source of p-type dopant for subsequent incorporation into portions of the GaN layer in one or more V-pits of active layer 520 and electron blocking layer 525. This facilitates the formation of portions of p-GaN layer 535 in one or more V-pits.

In some embodiments, the device 500 includes a first electrode in electrical communication with the n-GaN layer 510, and a second electrode in electrical communication with the p-GaN layer 535. The electrodes enable application of an electric potential (voltage) across the active layer 520. In some cases, the first and second electrodes are in electrical contact with the n-GaN layer 510 and the p-GaN layer 535, respectively. In other examples, one or both of the first and second electrodes are in electrical contact with the n-GaN layer 510 and the p-GaN layer 535 through one or more intermediate layers. In an example, the second electrode is in electrical communication with the p-GaN layer through a transparent conductive layer (not shown), such as an Indium Tin Oxide (ITO) layer.

Recombination of electrons and holes in the active layer 520, such as when a potential is applied across the active layer 520, generates light that is output in a direction generally away from the substrate 502. Alternatively, the layer 505 and 535 is transferred to another substrate 540, followed by removal of the substrate 505. Recombination of electrons and holes in the active layer 520 generates light, which then passes through the n-GaN layer and out of the device 500 in a direction generally away from the substrate 540. In some examples, device 500 includes additional layers between p-GaN layer 535 and substrate 540.

In some embodiments, the substrate 505 is formed from one or more of silicon, silicon dioxide, sapphire, zinc oxide, carbon (e.g., graphite), SiC, AlN, GaN, spinel (spinel), coated silicon (coated silicon), silicon-on-oxide, silicon carbide-on-oxide, glass, gallium nitride, indium nitride, titanium dioxide, aluminum nitride, a metallic material (e.g., copper), and combinations (or alloys) of these. In some cases, substrate 505 is formed of silicon. In an example, the substrate 505 may be formed of n-type silicon. In such an example, the electrode may be formed in contact with the substrate 505, i.e., in electrical communication with the n-GaN layer 510.

In some cases, the device 500 includes one or more additional layers between the substrate 505 and the n-GaN layer 510. The one or more additional layers may include a buffer layer, a stress relief layer, or a stress-creating layer. In an embodiment, the device 500 includes an aluminum gallium nitride layer adjacent to the substrate, and one or more u-type GaN (i.e., undoped or unintentionally doped GaN) layers adjacent to the aluminum gallium nitride layer. One or more u-GaN layers are disposed adjacent to the n-GaN layer 510.

In some cases, the electron blocking layer 525 is formed of aluminum gallium nitride (AlGaN). In some examples, the AlGaN layer can be compositionally graded in terms of aluminum and gallium.

In some embodiments, delta doped layer 530 is the interface between electron blocking layer 525 and p-GaN layer 535. In some examples, device 500 has a secondary ion mass spectrometry (sims) profile exhibiting coincident Mg and In peaks at the interface between electron blocking layer 525 and p-GaN layer 535.

In some examples, the peak indium intensity observed in delta doped layer 530, as measured by SIMS, is 1/100 or less orders of magnitude of the peak indium intensity (or concentration) observed in the individual quantum wells within active layer 520. The location of the peak indium concentration coincides with the location of the peak magnesium concentration at the interface between the AlGaN layer and the p-GaN layer 535.

In some embodiments, a light emitting device having V pits (or V defects) has a uniform p-type dopant profile in a p-GaN layer of the light emitting device. This advantageously enables the use of device structures (e.g., active layers) having moderate to high defect densities and minimizes, if not eliminates, problems associated with such device structures provided herein, such as inconsistent dopant concentrations.

Method for forming light emitting device

In another aspect of the invention, a method for forming a light emitting device is provided. Such methods provide for the formation of devices described herein, such as light emitting diodes, including III-V LEDs (e.g., GaN-based LEDs).

In some embodiments, a method for forming a light emitting device, such as a Light Emitting Diode (LED), includes forming a p-type group III-V semiconductor layer over (or adjacent to) an active layer in a reaction chamber, the p-type group III-V semiconductor layer extending into one or more V-pits of the active layer, including any intervening layers (e.g., electron blocking layers) between the p-type group III-V semiconductor layer and the active layer. The p-type group III-V semiconductor layer is formed by delta doping the wetting layer with a p-type dopant and introducing a group III source gas and a group V source gas into the reaction chamber. A source gas of p-type dopant is introduced to control the concentration of the p-type dopant in the p-type III-V layer. An active layer is formed over (or adjacent to) the n-type group III-V semiconductor layer. An n-type group III-V semiconductor layer is formed by introducing a group III source gas, a group V source gas, and a source gas of an n-type dopant into a reaction chamber.

The p-type group III-V semiconductor layer includes a group III-V semiconductor and a p-type dopant. The n-type group III-V semiconductor layer includes a group III-V semiconductor and an n-type dopant. Group III-V semiconductors include group III materials and group V materials. In an embodiment, the group III species includes gallium and/or indium. In another embodiment, the group V species is nitrogen.

In some embodiments, a method for forming a light emitting device, such as an LED, includes forming a p-type group III-V semiconductor layer over a substrate in a reaction chamber adjacent to an active layer, the p-type group III-V semiconductor layer extending into one or more V-pits of the active layer. The p-type group III-V semiconductor layer is formed by delta doping the wetting layer with a p-type dopant and introducing a source gas of a group III species and a source gas of a group V species into the reaction chamber. A wetting layer is formed adjacent to the active layer. In some cases, an electron blocking layer is formed adjacent to the active layer prior to forming the wetting layer. In an embodiment, an active layer is formed adjacent to an n-type group III-V semiconductor layer. In another embodiment, an n-type group III-V semiconductor layer is formed adjacent to a substrate.

In a particular embodiment, a method for forming a light emitting device, such as a Light Emitting Diode (LED), includes forming a p-type gallium nitride (p-GaN) layer over (or adjacent to) an active layer in a reaction chamber, the p-GaN layer extending into one or more V-pits of the active layer, including any intervening layers (e.g., electron blocking layers) between the p-GaN layer and the active layer. The p-GaN layer is formed by delta doping the wetting layer with a p-type dopant and introducing a gallium source gas and a nitrogen source gas into the reaction chamber. A source gas of p-type dopant is introduced to control the concentration of p-type dopant in the p-GaN layer.

In an embodiment, a wetting layer is formed adjacent to the active layer. In some examples, the light emitting device includes an electron blocking layer between the wetting layer and the active layer. In some cases, an electron blocking layer is formed adjacent to the active layer prior to forming the wetting layer. The active layer is formed on (or adjacent to) an n-type GaN ("n-GaN") layer. An n-GaN layer is formed over (or adjacent to) the substrate.

In other embodiments, a method for forming a Light Emitting Diode (LED) includes forming an n-GaN layer adjacent to a substrate in a reaction chamber, forming an active layer over the substrate, forming an electron blocking layer over the active layer, and forming a delta doped layer over the electron blocking layer. The delta doped layer is formed by delta doping the wetting layer with a p-type dopant.

In some cases, delta doping the wetting layer includes pulsing a precursor of a p-type dopant into a reaction chamber having the substrate. The precursor of the p-type dopant is pulsed in for a duration of between about 0.01 seconds and 20 minutes, or between about 0.1 seconds and 15 minutes, or between about 1 second and 10 minutes.

Fig. 6 illustrates a method 600 having a process flow diagram for forming a light emitting device according to an embodiment of the present invention. In a first operation 605, a substrate is provided in a reaction chamber configured to grow one or more device structures (or layers) of a light emitting device. In an example, the reaction chamber is a chamber under vacuum or an inert gas environment.

For example, the reaction chamber can be a vacuum chamber, such as an Ultra High Vacuum (UHV) chamber. In instances where a low pressure environment is desired, the reaction chamber may be evacuated by means of a pumping system having one or more vacuum pumps, such as one or more turbomolecular ("turbo") pumps, cryogenic pumps (cryopumps), ion pumps, and diffusion pumps (diffusional pumps) and mechanical pumps. The reaction chamber may include a control system for regulating precursor flow rates, substrate temperature, chamber pressure, and chamber evacuation.

Next, in a second operation 610, an n-GaN layer is formed over the substrate. In an embodiment, an n-GaN layer is formed by introducing a gallium precursor, a nitrogen precursor, and a precursor of an n-type dopant into a reaction chamber. Gallium precursors include one or more of trimethyl gallium (TMG), triethyl gallium (di-ethyl gallium) chloride, diethyl gallium chloride, and coordinated gallium hydride compounds (e.g., dimethyl gallium chloride). The nitrogen precursor comprises ammonia (NH)₃) Nitrogen (N)₂) And plasma-excited ammonia and/or N₂One or more of (a). In some examples, the precursor of the n-type dopant is silane (silane).

In an embodiment, a gallium precursor, a nitrogen precursor, and a precursor for an n-type dopant are introduced into the reaction chamber simultaneously. In another embodiment, the gallium precursor, the nitrogen precursor, and the n-type dopant precursor are introduced into the reaction chamber in an alternating and sequential manner (e.g., pulsed manner).

Next, in an optional third operation 615, a pit generation layer is formed over the n-GaN layer. The pit generation layer is formed by introducing a gallium precursor and a nitrogen precursor, and in some examples an indium precursor, into the reaction chamber. In some cases, the pit generation layer is formed of GaN, InGaN, and many combinations thereof, including InGaN/GaN superlattices. In some examples, the pit generation layer is optional if one or more sub-layers of the multiple quantum well active layer are used to generate pits.

Next, in a fourth operation 620, an active layer is formed over the n-GaN layer or the pit generation layer (if formed in operation 615). In an example, the active layer is a multiple quantum well active layer including alternating InGaN well layers and GaN barrier layers. The active layer is formed during the period in which the gallium source gas and the nitrogen source gas enter the reaction chamber to form the barrier layer, and the indium source gas is introduced to form the well layer. The indium source gas includes one or more of trimethylindium (trimethylindium), triethylindium (triethylindium), diethylindium chloride (diethylindium chloride), and coordinated indium hydride compounds (e.g., dimethylindium hydride) the source gases used to form the separate barrier layers and the well layers are introduced into the chamber simultaneously, or in other instances, in an alternating and sequential manner.

Next, in a fifth operation 625, an electron blocking layer is formed over the active layer. In the example where the electron blocking layer includes aluminum gallium nitride, the electron blocking layer is formed by introducing a gallium source gas, a nitrogen source gas, and an aluminum source gas into the reaction chamber. In some cases, the aluminum source gas comprises one or more of tri-isobutylaluminum (TIBAL), Trimethylaluminum (TMA), Triethylaluminum (TEA), and dimethylaluminum hydride (DMAH). In some cases, the electron blocking layer comprises aluminum indium gallium nitride (AIInGaN), in this example, an indium source gas such as Trimethylindium (TMI) is used in combination with other source gases. In other embodiments, the electron blocking layer is eliminated in some examples.

Next, in a sixth operation 630, a wetting layer is formed over the electron blocking layer (or the active layer if the electron blocking layer has been eliminated). The wetting layer is formed by introducing a source gas that wets the material, such as trimethyl indium (TMI) if the wetting material is indium, into the reaction chamber.

Next, in a seventh operation 635, the wetting layer is contacted with a source gas of a p-type dopant. In practice, the wetting layer is delta doped by pulsing a source gas of a p-type dopant into the reaction chamber. Delta doping the wetting layer forms a delta doped layer. In some examples, the delta doped layer is a p-type dopant implant layer. In an example, the p-type dopant is magnesium, and the wetting layer is delta-doped with magnesium by introducing biscyclopentadienyl magnesium (Cp2Mg) into the reaction chamber.

In an example, the wetting layer is formed at a first temperature in operation 630 and delta doped at the same or similar temperature to form a delta doped layer in operation 635. However, in other examples, the wetting layer is formed at a first temperature and delta doped with a p-type dopant at a second temperature different from the first temperature. In an embodiment, the wetting layer and/or delta doped layer is formed at a temperature between about 700 ℃ and 1100 ℃. In other embodiments, the wetting layer and/or delta doped layer is formed at a temperature between about 800 ℃ and 1050 ℃, while in other embodiments, the wetting layer and/or delta doped layer is formed at a temperature between about 850 ℃ and 1000 ℃.

In an example, the wetting layer is delta doped by pulsing a source gas of a p-type dopant into the reaction chamber. In an embodiment, the source gas for the p-type dopant is pulsed for a duration between 0.01 seconds and 20 minutes. In other embodiments, the source gas for the p-type dopant is pulsed for a duration between 0.1 seconds and 15 minutes, while in other embodiments, the source gas for the p-type dopant is pulsed for a duration between 1 second and 10 minutes.

In the illustrated example, operation 635 follows operation 630. However, in some examples, operations 630 and 635 occur simultaneously. That is, the source gas for the wetting material and the source gas for the p-type dopant are simultaneously introduced into the reaction chamber. In an example, at N₂Trimethylindium (TMI), biscyclopentadienylmagnesium (Cp2Mg), and ammonia are introduced into the reaction chamber with the aid of a carrier gas and are in contact with the electron blocking layer (e.g., AlGaN) formed in operation 625. Cp2Mg may flow into the reaction chamber before, simultaneously with, or after providing TMI. In an example, operation 635 precedes operation 630, i.e., the electron blocking layer is contacted with a source of a p-type dopant (e.g., Cp2Mg) to form a p-type dopant layer over the electron blocking layer, which is then contacted with a source gas of a wetting material (e.g., TMI).

Next, in an eighth operation 640, a p-type gallium nitride (p-GaN) layer is formed over (or adjacent to) the delta doped layer. In some embodiments, no actual growth of the p-GaN layer occurs during the formation of the delta doped layer.

The p-GaN layer is formed by introducing a gallium source gas (or precursor) and a nitrogen source gas into a reaction chamber. In an embodiment, a source gas for the p-type dopant is not introduced into the reaction chamber containing the gallium source gas and the nitrogen source gas. In this example, when the gallium source gas and the nitrogen source gas are brought into contact with the Δ doping layer, the GaN layer starts to be formed on the Δ doping layer. Incorporating the p-type dopant of the delta-doped layer into the GaN layer accompanies growth of the GaN layer, thereby forming p-GaN, accompanied by consumption of the delta-doped layer in the p-type dopant. A source gas of p-type dopant is introduced into the reaction chamber for a predetermined period of time, and the formation of the p-GaN layer is continued. In some examples, the continued flow of the gallium source gas and the nitrogen source gas accompanies the source gas of the p-type dopant. The delta doping layer enables doping of the GaN layer in one or more V-pits of the active layer and the electron blocking layer (to form p-GaN). Subsequent introduction of a source gas of p-type dopants provides p-type dopants for continued growth of the p-GaN layer in portions of the p-GaN layer above the active layer (and not in the V-pits).

In an example, the p-GaN layer includes a first portion and a second portion (see, e.g., fig. 4). The first portion is disposed over the electron blocking layer outside of the one or more V-pits and forms a second portion in the one or more V-pits. During the growth of the second portion, p-type dopants for the p-GaN layer are provided by the delta-doped layer. After the second portion is formed, a source gas for the p-type dopant (or another source gas for the p-type dopant) is introduced to provide a predetermined concentration of the p-type dopant in the first portion.

In some cases, the source gases are introduced into the reaction chamber with the aid of a carrier gas and/or pumping. The carrier gas may be an inert gas, such as H₂Ar and/or N₂. In an example, at N₂With the aid of a gallium source gas (e.g., TMG) and a nitrogen source gas (e.g., NH)₃) Is introduced into the reaction chamber. In another example, a gallium source gas, a nitrogen source gas, and a source gas of a p-type dopant are introduced into the reaction chamber with the aid of a pumping system (e.g., a turbo pump).

May be evacuable between some or all of the independent operationsA reaction chamber. In some examples, the reaction chamber is purged by means of a purge gas (purgegas) or vacuum (pumping) system. In an example, the reaction chamber is evacuated between operations 620 and 625 by means of a purge gas. The purge gas may be the same or similar to the carrier gas. In an example, the purge gas is N₂And by continuing to make N₂The flow into the reaction chamber is stopped while the flow of the one or more source gases is stopped to purge the reaction chamber. In another example, the reaction chamber is evacuated (i.e., a vacuum is applied to the reaction chamber) between operations 610 and 615 by way of a pumping system. In other examples, the reaction chamber is purged with a purge gas or vacuum system.

Although the method 600 is described as occurring in a reaction chamber, in some cases, one or more operations of the method 600 may occur in a separate reaction chamber. In an example, operations 605 and 610 are performed in a first reaction chamber, operation 615 and 625 are performed in a second reaction chamber, and operation 630 and 640 are performed in a third reaction chamber. The reaction spaces may be fluidly isolated from each other, such as in separate locations.

Fig. 7 shows a pressure versus time pulse plot for forming a delta doped layer and a p-GaN layer over the delta doped layer. Pressure (y-axis) is shown as a function of time (x-axis). The pressure may correspond to a partial pressure of each source gas in the reaction chamber. For a substrate in a reaction chamber, at a first time (t)₁) In N at₂With the aid of a carrier gas, TMI and NH₃Is introduced into the reaction chamber. This forms a wetting layer on the substrate. Next, by means of a second time (t)₂) The Cp2Mg introduced into the reaction chamber delta-dopes the wetting layer with Mg. Maintaining NH during the pulsed addition of Cp2Mg to the reaction chamber₃And N₂The flow rate of (c). A time period for Cp2Mg exposure is less than a time period of TMI; however, in some cases, the time period for Cp2Mg exposure (i.e., pulse duration) is greater than or equal to the time period for TMI exposure. The Cp2Mg pulse overlaps the TMI pulse. In other examples, the Cp2Mg pulse does not overlap the TMI pulse. In an example, the Cp2Mg pulse precedes the TMI pulse. In another example, the Cp2Mg pulse follows the TMI pulse.

Next, at a third time (t)₃) TMG is introduced into the reaction chamber. Prior to the introduction of TMG, the flow rate of Cp2Mg was stopped, but NH was maintained₃And N₂The flow rate of (c). Next, at a fourth time (t)₄) Cp2Mg is introduced into the reaction chamber to provide a p-type dopant for forming a p-GaN layer. The delta doped layer provides a p-type dopant (Mg) for incorporation into the V-pits upon GaN deposition, which forms p-GaN in the V-pits. The second dose of Cp2Mg provides a p-type dopant for subsequent growth of a p-GaN layer over the substrate and outside the V-pits.

One or more layers of the light emitting devices provided herein can be formed by vapor (or vapor) deposition techniques. In some embodiments, one or more layers in light emitting devices provided herein are formed by Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD), plasma enhanced CVD (pecvd), plasma enhanced ALD (peald), metal organic CVD (mocvd), hot wire CVD (hwcvd), initial CVD (icvd), modified CVD (mcvd), vapor axial deposition (vapor axial deposition, VAD), Outside Vapor Deposition (OVD), and/or physical vapor deposition (e.g., sputter deposition, evaporation deposition).

Although the methods and structures provided herein are described in the context of light emitting devices having certain group III-V semiconductor materials, such as gallium nitride, the methods and structures are applicable to other types of semiconductor materials. The methods and structures provided herein may be used for light emitting devices having active layers formed of gallium nitride (GaN), indium gallium nitride (InGaN), zinc selenide (ZnSe), aluminum nitride (AlN), aluminum gallium nitride (AlGaN), aluminum gallium indium nitride (AlGaInN), and zinc oxide (ZnO).

In some embodiments, the layers and device structures provided herein, such as, for example, active layers (including well layers and barrier layers), n-type group III-V semiconductor layers, p-type group III-V semiconductor layers, are formed with the aid of a controller configured to adjust one or more process parameters, such as substrate temperature, precursor flow rate, growth rate, hydrogen gas flow rate, and reaction chamber pressure. The controller includes a processor configured to facilitate execution of machine executable code configured to implement the methods provided herein.

Examples of the use of

A substrate having an AlGaN electron blocking layer over an active layer is provided in a reaction chamber. The active layer and the electron blocking layer include a plurality of V-pits. A p-GaN layer is formed on the AlGaN electron blocking layer by initially forming a p-type delta doped layer. At a substrate temperature between about 850 ℃ and 1000 ℃ in N₂Trimethylindium (TMI) and ammonia (NH) with the aid of a carrier gas₃) Are provided into the reaction chamber and brought into contact with the electron blocking layer to form a wetting layer. Next, the wetting layer is delta doped with magnesium by introducing Cp2Mg into the reaction chamber and exposing the wetting layer to Cp2 Mg. In some examples, Cp2Mg is provided to the reaction chamber before, simultaneously with, or after the TMI flows into the reaction chamber. Next, a GaN layer was formed on the Δ -doped layer by introducing TMG into the reaction chamber. The p-type dopant in the delta-doped layer provides a p-type dopant in the GaN layer for incorporation into the V-pits. Before or after the p-GaN layer is filled with V pits, together with TMG and NH₃Together with a source gas of p-type dopant, is introduced into the reaction chamber. The timing of the source gas for the p-type dopant is selected to provide a p-type dopant concentration, profile, and/or desired profile.

As used throughout this specification and the claims, the singular or plural referents include the plural or singular, respectively, unless otherwise specified. Moreover, the words "herein," "beneath," "above," "below," and words of similar import, refer to this application as a whole and not to any particular portions of this application. When the word "or" is used in reference to a listing of two or more items, the word encompasses all of the following interpretations of the word: any item within the manifest, all items within the manifest, and any combination of items within the manifest.

It will be appreciated from the foregoing that, while particular implementations have been illustrated and described, numerous modifications may be made and envisioned herein. Neither is the invention intended to be limited to the specific examples provided in this document. While the present invention has been described with reference to the above application documents, the descriptions and examples of the embodiments of the present invention herein are not intended to be limiting. Further, it is to be understood that all aspects of the present invention are not limited to the specific illustrations, configurations, or relative proportions set forth herein in accordance with a number of conditions and variables. Many modifications in form and detail of the embodiments of the invention will be apparent to those skilled in the art. It is therefore contemplated that the present invention shall also cover any such modifications, variations and equivalents.

Claims (21)

1. A light emitting diode comprising:

an n-type GaN layer doped with an n-type dopant;

an active layer adjacent to the n-type GaN layer, the active layer including In and having one or more V-pits;

a p-type delta doped layer adjacent to the active layer, the p-type delta doped layer comprising In delta doped with Mg; and

a p-type GaN layer adjacent to the p-type delta doped layer, the p-type GaN layer doped with a p-type dopant, the p-type GaN layer having a first portion disposed above the active layer and a second portion that is a portion of the p-type GaN layer laterally bounded by the one or more V-pits,

wherein Mg intensity has a peak In the p-type Δ doped layer, and In intensity has a first peak In the p-type Δ doped layer and a second peak In the active layer, the first peak In the p-type Δ doped layer being lower than the second peak In the active layer.

2. The light emitting diode of claim 1, wherein the concentration of the p-type dopant in the first portion is at least 1x10²⁰cm^-3。

3. The light emitting diode of claim 1, further comprising a silicon substrate adjacent to the n-type GaN layer.

4. The light emitting diode of claim 1, wherein the active layer has 1x10⁸cm^-2And 5x10⁹cm^-2Dislocation density in between.

5. The light emitting diode of claim 1, wherein the p-type GaN layer extends into the one or more V-pits of the active layer.

6. The light emitting diode of claim 1, wherein the concentration of the p-type dopant in the second portion is at least 1x10²⁰cm^-3。

7. The light emitting diode of claim 1, wherein the first peak In intensity In the p-type delta doped layer is 1/100 or less of the second peak In intensity In the active layer.

8. The light emitting diode of claim 1, further comprising an electron blocking layer between the active layer and the p-type delta doped layer.

9. The light emitting diode of claim 1, wherein the peak of Mg intensity In the p-type delta doped layer coincides with the first peak of In intensity In the p-type delta doped layer.

10. A light emitting diode comprising:

an n-type GaN layer;

an active layer adjacent to the n-type GaN layer, the active layer including In and including one or more V-pits;

an electron blocking layer adjacent to the active layer; and

a p-type GaN layer adjacent to the electron blocking layer,

wherein the light emitting diode includes Mg and In at an interface between the electron blocking layer and the p-type GaN layer, Mg intensity has a peak at the interface, and In intensity has a first peak at the interface and In intensity has a second peak In the active layer, the first peak of In intensity at the interface being lower than the second peak of In intensity In the active layer.

11. The light emitting diode of claim 10, wherein the active layer has 1x10⁸cm^-2And 5x10⁹cm^-2Dislocation density in between.

12. The light emitting diode of claim 10, wherein the first peak of In intensity at the interface is 1/100 or less of the second peak of In intensity In the active layer.

13. The light emitting diode of claim 10, wherein the peak of Mg intensity at the interface coincides with the first peak of In intensity at the interface.

14. The light emitting diode of claim 10, wherein the interface is a layer comprising In and N.

15. The light emitting diode of claim 10, wherein the p-type GaN layer extends into the one or more V-pits of the active layer.

16. The light emitting diode of claim 10, wherein the p-type GaN layer has a first portion and a second portion, wherein the first portion is disposed above the active layer and the second portion is a portion of the p-type GaN layer laterally bounded by the one or more V-pits.

17. The light emitting diode of claim 16, wherein the concentration of the p-type dopant in the second portion is at least 1x10²⁰cm^-3。

18. A method for forming a light emitting diode, comprising:

forming a p-type group III-V semiconductor layer adjacent to an active layer over a substrate in a reaction chamber, the p-type group III-V semiconductor layer extending into one or more V-pits of the active layer,

wherein the p-type group III-V semiconductor layer is formed as follows:

delta doping a wetting layer with magnesium, the wetting layer comprising indium, wherein the magnesium intensity has a peak in the delta doped layer and the indium intensity has a first peak in the delta doped layer and a second peak in the active layer, the first peak in the delta doped layer being lower than the second peak in the active layer; and

a source gas of a group III species and a source gas of a group V species are introduced into the reaction chamber.

19. The method of claim 18, wherein an electron blocking layer is formed adjacent to the active layer prior to forming the wetting layer.

20. The method of claim 18, wherein delta doping comprises pulsing a precursor of Mg into a reaction chamber in which the substrate is disposed.

21. The method of claim 20, wherein the precursor of Mg is pulsed in a duration between 0.1 seconds and 15 minutes.