CN111900240A - High-brightness LED and preparation method thereof - Google Patents

Abstract

The invention discloses a high-brightness LED and a preparation method thereof, comprising a substrate on which a buffer layer, lightly doped and heavily doped nitride alternating layers, an MQW active layer and a p-type semiconductor layer are grown in sequence , the exposed part of the upper surface of the lightly doped and heavily doped nitride alternating layers is provided with n electrodes, and the p-type semiconductor layer is provided with p electrodes; the lightly doped and heavily doped nitride alternating layers are The lightly doped nitride layer and the heavily doped nitride layer are alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers formed by electrochemical etching, respectively. The high-brightness LED and the preparation method thereof disclosed in the invention can improve the luminous efficiency while reducing the cost, and have high repeatability, which is beneficial to practical application.

Description

A kind of high brightness LED and preparation method thereof

technical field

The invention relates to the technical field of LEDs, in particular to a high-brightness LED and a preparation method thereof.

Background technique

As group III nitride wide-bandgap semiconductor materials and devices are more widely used in optoelectronics and power electronics such as lighting, display, communication, and medical care, nitride wide-bandgap semiconductor materials and devices, as the representative of the third-generation semiconductor, have become the most widely used in the world. A new generation of fields vying for preemption. Due to the characteristics of small size, low cost, good monochromaticity and high efficiency, LEDs have broad application prospects in the fields of lighting, display and optical communication, and have become a new generation of electronic information technology - a research hotspot in the field of optoelectronics.

The main research work of LED focuses on improving its luminous efficiency and reducing cost. Using a simple growth and preparation process to improve the luminous efficiency of the LED is a very effective means to improve the performance of the LED and reduce the cost. One method is to make use of the light lost from the backside by epitaxy or preparing a highly reflective layer under the LED light-emitting layer, thereby increasing the light-emitting intensity of the LED.

At present, the techniques used include epitaxial growth of AlGaN/GaN or AlInN/GaN reflective structures; there are also substrate removal and grinding and polishing techniques using dielectric reflective layers or metal reflective layer structures. Devices prepared by epitaxial growth technology often require a long growth time, or DBR cracks due to stress caused by lattice mismatch; increase the cost of epitaxy and increase the difficulty of the process; through laser lift-off, metal bonding and mechanical polishing processes The preparation of optoelectronic devices is not only difficult to control due to the substrate polishing and thinning process, but also increases the process cost.

Therefore, up to now, due to the lack of effective high-brightness LEDs prepared by simple processes, the high-brightness LED manufacturing process is complicated and costly, and it is difficult to control. Therefore, it is necessary to develop a technology with simple growth and preparation process and low cost to realize the preparation of high-brightness LED and overcome the bottleneck restricting its application.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a high-brightness LED and a preparation method thereof, so as to achieve the purpose of reducing the cost and improving the luminous efficiency.

For achieving the above object, technical scheme of the present invention is as follows:

A high-brightness LED, comprising a substrate on which a buffer layer, lightly doped and heavily doped nitride alternating layers, an MQW active layer, and a p-type semiconductor layer are grown in sequence, and the lightly doped and heavily doped nitride layers are sequentially grown on the substrate. The exposed part of the upper surface of the doped nitride alternate layer is provided with an n electrode, and the p-type semiconductor layer is provided with a p electrode; the lightly doped and heavily doped nitride alternate layers are lightly doped nitride layers and heavy doped nitride layers. The doped nitride layers are alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers formed by electrochemical etching.

In the above solution, the low-porosity porous nitride layer and the high-porosity porous nitride layer are alternately stacked to form a reflective structure, and the logarithm of the alternating structure is greater than or equal to 1.

In the above solution, the substrate is sapphire, silicon, silicon carbide or glass; the material of the buffer layer is one or a combination of AlN, GaN, and AlGaN.

In the above solution, the dopant of the lightly doped nitride layer and the heavily doped nitride layer is silicon or germanium, and the doping concentration of the heavily doped nitride layer is 5×10 ¹⁸ to 2×10 ²⁰ cm ^{− 3.} The doping concentration of the lightly doped nitride layer is 1×10 ¹⁸ to 5×10 ¹⁸ cm ^-3 .

In the above solution, both the n-electrode and the p-electrode are metal electrodes, selected from one of Ti, Al, Ni, Au, and Cr metals or any combination thereof.

In the above solution, the p-type semiconductor layer is magnesium-doped AlGaN, AlInN, AlInGaN or GaN, and the magnesium-doped doping concentration is 2×10 ¹⁸ to 1×10 ²⁰ cm ⁻³ .

In the above solution, the MQW active layer is InGaN, AlGaN, AlGaInN or GaN.

In the above solution, the nitride of the lightly doped nitride layer and the heavily doped nitride layer refers to GaN, InGaN, AlGaN, AlInN or AlInGaN.

A preparation method of a high-brightness LED, comprising the following steps:

(1) A buffer layer, a lightly doped and heavily doped nitride alternate layer are sequentially grown on the upper surface of the substrate, and an MQW active layer and a p-type semiconductor layer are sequentially grown on the upper surface of the lightly doped and heavily doped nitride doped alternate layers. ;

(2) The LED pattern is formed by photolithography, dry etching and cleaning process, and part of the lightly doped and heavily doped nitride alternating layers are exposed;

(3) The lightly doped and heavily doped nitride alternating layers are etched by selective electrochemical etching to form alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers. The structure is as follows: Porous conductive reflective structure;

(4) An n-electrode is prepared on the upper surface of the exposed lightly doped and heavily doped nitride alternating layers, and a p-electrode is prepared on the upper surface of the p-type semiconductor layer.

Through the above technical solutions, a high-brightness LED and a preparation method thereof provided by the present invention have the following beneficial effects:

1. The high-brightness LED of the present invention has a simple structure, greatly shortens the epitaxy process time, low cost, and high repeatability, which is beneficial to practical application.

2. The n-electrode is fabricated on the alternate layer of lightly doped and heavily doped nitride, and the alternate layer of lightly doped and heavily doped nitride is directly used as the n-type conductive layer, which can simplify the structure of the LED; Alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers are prepared alternately with heavily doped nitride layers, and the porous nitride structure is used as a high-reflectivity reflective structure to direct the light emitted from the MQW active region. After emission, it is reflected through the high-reflectivity porous structure, which reduces the optical path difference of the reflected light of the LED, effectively improves the luminous efficiency of the LED, and improves the brightness.

3. In addition, since the porous nitride layer is formed by etching alternate layers of lightly doped and heavily doped nitrides by selective electrochemical etching, no additional stress will be added, and by optimizing the doping of the porous nitride layer The concentration and thickness make it have good electrical conductivity, which can improve the optoelectronic properties of the LED while reducing the difficulty of the preparation process.

4. The present invention combines the n-type conductive layer and the reflective layer into one layer, which effectively simplifies the structure of the LED, thereby shortening the LED epitaxy process time and effectively reducing the epitaxy process cost.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that are required in the description of the embodiments or the prior art.

1 is a schematic structural diagram of a high-brightness LED according to an embodiment of the present invention;

2 is a flowchart of a method for manufacturing a high-brightness LED according to an embodiment of the present invention;

Figure 3 is a SEM cross-sectional view of a high-brightness LED;

4 is a comparison diagram of the luminescence spectrum of an LED with a porous nitride reflective structure and an existing non-porous nitride reflective structure according to the present invention;

FIG. 5 is a comparison diagram of the optoelectronic characteristics of the LED with the porous nitride reflective structure of the present invention and the existing non-porous nitride reflective structure.

In the figure, 1-substrate, 2-buffer layer, 3-lightly doped and heavily doped nitride alternate layers, 4-MQW active layer, 5-p-type semiconductor layer, 6-n electrode, 7-p electrode .

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

The present invention provides a high-brightness LED, as shown in FIG. 1 , comprising a substrate 1 on which a buffer layer 2 , a lightly doped and heavily doped nitride alternating layer 3 , and an MQW active layer 4 are grown in sequence. , p-type semiconductor layer 5, the exposed part of the upper surface of the lightly doped and heavily doped nitride alternate layer 3 is provided with n-electrode 6, and p-type semiconductor layer 5 is provided with p-electrode 7; as shown in FIG. 3, lightly doped The doped and heavily doped nitride alternating layers 3 are alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers formed by electrochemical etching of lightly doped nitride layers and heavily doped nitride layers, respectively.

In this embodiment, the low-porosity porous nitride layer and the high-porosity porous nitride layer are alternately stacked to form a reflective structure, and the logarithm of the alternating structure is equal to five.

The substrate 1 is sapphire, silicon, silicon carbide or glass; the material of the buffer layer 2 is one or a combination of AlN, GaN, and AlGaN.

In this embodiment, the dopant of the lightly doped nitride layer and the heavily doped nitride layer is silicon, the doping concentration of the heavily doped nitride layer is 2×10 ¹⁹ cm ⁻³ , and the lightly doped nitride layer has a doping concentration of 2×10 19 cm −3 . The doping concentration is 2×10 ¹⁸ cm ^-3 .

Both the n-electrode 6 and the p-electrode 7 are metal electrodes, selected from one of Ti, Al, Ni, Au, and Cr metals or any combination thereof.

In this embodiment, the p-type semiconductor layer 5 is magnesium-doped AlGaN, and the doping concentration of magnesium-doped is 2×10 ¹⁹ cm ⁻³ .

The MQW active layer 4 is InGaN or GaN.

In this embodiment, the nitride of the lightly doped nitride layer and the heavily doped nitride layer refers to GaN, InGaN, AlGaN, AlInN or AlInGaN.

A preparation method of a high-brightness LED of the present invention, as shown in FIG. 2 , includes the following steps:

(1) A buffer layer 2, a lightly doped and heavily doped nitride alternate layer 3 are sequentially grown on the upper surface of the substrate 1, and an MQW active layer 4 is sequentially grown on the upper surface of the lightly doped and heavily doped nitride doped alternate layer 3 and p-type semiconductor layer 5;

(2) The LED pattern is formed by photolithography, dry etching and cleaning process, and part of the lightly doped and heavily doped nitride alternating layers 3 are exposed;

(3) The lightly doped and heavily doped nitride alternating layers 3 are etched by selective electrochemical etching to form alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers, respectively. is a porous conductive reflective structure;

(4) An n-electrode 6 is prepared on the upper surface of the exposed lightly doped and heavily doped nitride alternating layers 3 , and a p-electrode 7 is prepared on the upper surface of the p-type semiconductor layer 5 .

As can be seen from FIG. 4 , the LED with the porous nitride reflective structure of the present invention, compared with the existing LED without the porous nitride reflective structure, due to its alternately stacked heavily doped nitride layers and lightly doped nitrogen layers The compound layer becomes a porous nitride reflective layer, and the luminous intensity is increased by a factor of 6.

It can be seen from Figure 5 that the luminous intensity of the LED obtained by electrochemical corrosion is increased by 150%. At the same time, after the electrochemical corrosion forms the porous nitride layer, the electrical characteristics of the LED are almost unchanged, indicating that the optoelectronic performance of the LED has been greatly improved. improve.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. a high-brightness LED, comprising a substrate, characterized in that a buffer layer, lightly doped and heavily doped nitride alternating layers, MQW active layers, p-type semiconductor layers are grown on the substrate successively, so The exposed part of the upper surface of the lightly doped and heavily doped nitride alternate layers is provided with n electrodes, and the p-type semiconductor layer is provided with p electrodes; the lightly doped and heavily doped nitride alternate layers are lightly doped The hetero-nitride layer and the heavily doped nitride layer are alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers formed by electrochemical etching, respectively. 2 . The high-brightness LED according to claim 1 , wherein the low-porosity porous nitride layer and the high-porosity porous nitride layer are alternately stacked to form a reflective structure, and the logarithm of the alternating structure is greater than or equal to 1. 3 . . 3. A high-brightness LED according to claim 1, wherein the substrate is sapphire, silicon, silicon carbide or glass; the material of the buffer layer is one of AlN, GaN, AlGaN or several combinations. 4. A high-brightness LED according to claim 1, wherein the dopants of the lightly doped nitride layer and the heavily doped nitride layer are silicon or germanium, and the dopant of the heavily doped nitride layer is silicon or germanium. The doping concentration is 5×10 ¹⁸ -2×10 ²⁰ cm ^-3 , and the doping concentration of the lightly doped nitride layer is 1×10 ¹⁸ -5×10 ¹⁸ cm ^-3 . 5 . The high-brightness LED according to claim 1 , wherein the n-electrode and the p-electrode are both metal electrodes, selected from one of Ti, Al, Ni, Au, and Cr metals or any combination thereof. 6 . 6 . The high-brightness LED according to claim 1 , wherein the p-type semiconductor layer is magnesium-doped AlGaN, AlInN, AlInGaN or GaN, and the magnesium-doped doping concentration is 2×10 ¹⁸ ～1 . ×10 ²⁰ cm ^-3 . 7 . The high-brightness LED according to claim 1 , wherein the MQW active layer is InGaN, AlGaN, AlGaInN or GaN. 8 . 8 . The high-brightness LED according to claim 1 , wherein the nitrides of the lightly doped nitride layer and the heavily doped nitride layer refer to GaN, InGaN, AlGaN, AlInN or AlInGaN. 9 . 9. a preparation method of high brightness LED, is characterized in that, comprises the steps: (1) A buffer layer, a lightly doped and heavily doped nitride alternate layer are sequentially grown on the upper surface of the substrate, and an MQW active layer and a p-type semiconductor layer are sequentially grown on the upper surface of the lightly doped and heavily doped nitride doped alternate layers. ; (2) The LED pattern is formed by photolithography, dry etching and cleaning process, and part of the lightly doped and heavily doped nitride alternating layers are exposed; (3) The lightly doped and heavily doped nitride alternating layers are etched by selective electrochemical etching to form alternately stacked low-porosity porous nitride layers and high-porosity porous nitride layers. The structure is as follows: Porous conductive reflective structure; (4) An n-electrode is prepared on the upper surface of the exposed lightly doped and heavily doped nitride alternating layers, and a p-electrode is prepared on the upper surface of the p-type semiconductor layer.

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