TWI415301B - Nitride semiconductor emitting structure - Google Patents

Abstract

The present invention discloses a nitride semiconductor light emitting structure, suitable for emitting with a wavelength essentially ranged between 500 to 540 nm. The nitride semiconductor light emitting structure includes a P type nitride semiconductor layer, a N type nitride semiconductor layer and a nitride semiconductor active layer. The nitride semiconductor active layer is dispose between the P type nitride semiconductor layer and the N type nitride semiconductor layer. In addition, the nitride-based semiconductor active layer includes a plurality of pairs of quantum well structures, each of the pair of the quantum well is stacked into mezzanine shape. Moreover, each pair of quantum well structure includes a well layer and a barrier layer wherein the thickness of the barrier layer is between 10 to 25 nm.

Description

Nitride-based semiconductor light-emitting structure

The present invention relates to a nitride semiconductor light-emitting element comprising a light-emitting diode composed of a nitride semiconductor as a light-emitting layer material, and a laser diode, and the like, in particular, the active layer includes a plurality of pairs of quantum well structures, and the light-emitting main body thereof A nitride-based semiconductor light-emitting structure having a wavelength of 500 to 540 nm.

The principle of light-emitting diode (LED) that we know is to use energy difference between electrons moving between an n-type semiconductor and a p-type semiconductor to release energy in the form of light. Unlike the principle of illuminating the incandescent lamp, the illuminating diode is called a cold source. In addition, the light-emitting diode has the advantages of high durability, long life, light weight, low power consumption, etc., so its demand and importance are also increasing.

A conventional light-emitting diode includes a substrate, an N-type nitride-based semiconductor, a nitride-based semiconductor active layer, and a P-type nitride-based semiconductor layer on the substrate, which are stacked from bottom to top.

At present, a nitride-based semiconductor is grown on a substrate by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy or the like, and the substrate may be sapphire (α-Al 2 O 3 single crystal), any oxidation. Single crystal or III-V compound semiconductor single crystal. In general, the above-described N-type nitride-based semiconductor is doped with N-type ions (for example, Si ions). The P-type nitride-based semiconductor is formed by doping P-type ions (for example, Mg ions); the nitride-based semiconductor active layer has a multi-quantum well structure including a barrier layer and a well layer.

Furthermore, the industry often uses a multi-quantum well structure of well layer (InGaN)/barrier layer (GaN) as the active layer of blue or green LEDs. However, since the wavelength of green light is longer than blue light, the content of In in the green LED is therefore high, which causes a large stress in the epitaxial process. The reason is that the green LED requires a thicker barrier layer to release excess stress, but it also reduces the output speed of the epitaxial wafer.

In view of the increasing demand for green LEDs, and in order to increase the output speed and achieve the luminous efficiency, the inventors have developed an improved thinned nitride-based semiconductor light-emitting structure that not only effectively increases the production speed, but also improves the residual stress residue. At the same time, it can reduce the epitaxial defects and achieve the effect of luminous efficiency.

In view of the problems of the prior art, the object of the present invention is to provide a nitride-based semiconductor light-emitting structure having a dominant wavelength of light between 500 and 540 nm, and the nitride-based semiconductor light-emitting structure is characterized by a nitride. The semiconductor active layer comprises a plurality of pairs of quantum well structures, and each pair of quantum well structures comprises a well layer and a barrier layer, wherein each barrier layer has a thickness between 10 and 25 nanometers.

According to the object of the present invention, the inventors propose a nitride-based semiconductor light-emitting structure comprising: a P-type nitride-based semiconductor layer, a N A nitride-based semiconductor layer and a nitride-based semiconductor active layer. The nitride-based semiconductor active layer is formed between the P-type nitride-based semiconductor layer and the N-type nitride-based semiconductor layer. In detail, the active layer of the nitride-based semiconductor includes a complex pair of quantum well structures (MQW, Multi-Quantum Well), and each pair of quantum well structures is stacked to form a sandwich. In addition, each pair of quantum well structures includes a well layer and a barrier layer, the barrier layer having a band gap greater than the band gap of the well layer.

In summary, the nitride-based semiconductor light-emitting structure of the present invention comprises 4 to 15 pairs of quantum well structures. As a whole, it is similar that a plurality of well layers and barrier layers are repeatedly stacked on each other. However, at least two pairs of quantum well structures close to the N-type nitride-based semiconductor layer are defined as non-light-emitting regions; the remaining pairs of quantum well structures are defined as light-emitting regions. Wherein, the thickness of the barrier layer of the plurality of pairs of the quantum well structure in the non-light-emitting region is greater than the thickness of the barrier layer of the plurality of pairs of the quantum well structure by 5 to 10 nm. In detail, the thickness of the barrier layers of the plurality of pairs of quantum well structures in the non-light-emitting region is between 15 and 25 nm, preferably between 18 and 23 nm. Moreover, the thickness of the barrier layers of the plurality of pairs of quantum well structures in the light-emitting region is between 10 and 20 nm, preferably between 11 and 16 nm. In summary, the active layer of the nitride-based semiconductor of the present invention comprises a light-emitting region and a non-light-emitting region. Since the barrier layer of the non-light-emitting region is thick, the excess stress generated in the epitaxial process can be effectively reduced.

More specifically, both the illuminating region and the non-emissive region comprise at least two pairs of quantum well structures. Wherein, the composition of the well layer of the light-emitting area and the non-light-emitting area is gallium indium nitride (composition chemical formula: Ga _Y In _Z N, 0≦Y, Z≦1, Y+Z=1), and the composition of the barrier layer The composition is gallium nitride (GaN). However, the difference between the light-emitting region and the non-light-emitting region is not only that the thickness of the barrier layer is different, but on the other hand, the well layer of the non-light-emitting region is less doped with ions. Therefore, electrons and holes are not easily recombined in the non-light-emitting region, and most of the electrons and holes are concentrated in the light-emitting region to recombine, and the light is released in the photon mode to generate light, thereby effectively improving the luminous efficiency.

Further, the present invention further provides a nitride-based semiconductor light-emitting structure characterized in that the P-type nitride-based semiconductor layer and the N-type nitride-based semiconductor layer do not contain aluminum.

According to a preferred embodiment of the present invention, the nitride-based semiconductor light-emitting structure of the present invention comprises a substrate and a buffer layer, wherein the buffer layer is formed on the substrate body and the N-type nitride system The semiconductor layer is formed on the buffer layer body. Therefore, we can use the buffer layer to reduce the stress caused by the lattice difference between the substrate and the gallium nitride epitaxial layer, so that the epitaxial defects are reduced, and at the same time, the luminescent effect can be improved.

According to a preferred embodiment of the present invention, the nitride-based semiconductor light-emitting structure of the present invention comprises a substrate, a buffer layer and an undoped nitride-based semiconductor layer, wherein the buffer layer is formed on the substrate surface. The undoped nitride-based semiconductor layer is formed on the buffer layer surface, and the N-type nitride-based semiconductor layer is formed on the undoped nitride-based semiconductor layer surface. Of course, the N-type nitride-based semiconductor layer can also be formed directly on the substrate body.

Incidentally, the base material of the present invention may be a sapphire substrate, silicon carbide (SiC) substrate, silicon (Si) substrate, a gallium arsenide (CaAs) substrate, lithium aluminate (LiAlO ₂₎ substrate, lithium gallate (LiGaO ₂ ) A substrate, a gallium nitride substrate or an aluminum nitride (AlN) substrate.

According to the foregoing, the nitride-based semiconductor light-emitting structure according to the present invention may have one or more of the following features and advantages:

(1) The nitride-based semiconductor light-emitting structure of the present invention has a dominant wavelength of light of 500 to 540 nm, wherein the nitride-based semiconductor active layer includes a non-emission region and a light-emitting region, and the barrier layer of the non-emission region has a thickness greater than that of the light-emitting region. The barrier layer of the zone has a thickness of 5 to 10 nm.

(2) The nitride-based semiconductor light-emitting structure of the present invention, wherein the P-type nitride-based semiconductor layer and the N-type nitride-based semiconductor layer do not contain aluminum.

(3) The nitride-based semiconductor light-emitting structure of the present invention, wherein the plurality of pairs of quantum well structures in the non-light-emitting region enable release of excess stress generated in the epitaxial process.

The embodiments of the nitride-based semiconductor light-emitting structure according to the present invention will be described below with reference to the related drawings. For the sake of understanding, the same components in the following embodiments are denoted by the same reference numerals.

First, please refer to FIG. 1 and FIG. 2, which are schematic views of a first embodiment of a nitride-based semiconductor light-emitting structure of the present invention and a second implementation of the nitride-based semiconductor light-emitting structure of the present invention. A schematic diagram of an example. Considering this first embodiment, the nitride system is half The conductor active layer 3 is formed between the P-type nitride-based semiconductor layer 4 and the N-type nitride-based semiconductor layer 2, and has a dominant wavelength of light of between 500 and 540 nm. It is to be noted that the difference between the present invention and the prior art is that the P-type nitride-based semiconductor layer 4 and the N-type nitride-based semiconductor layer 2 do not contain aluminum. In addition, the nitride-based semiconductor active layer 3 includes a plurality of pairs of quantum well structures 300, and each pair of quantum well structures 300 are stacked in a sandwich shape. Here, only five pairs of quantum well structures 300 are exemplified, but are not limited. However, at least two pairs of quantum well structures close to the N-type nitride-based semiconductor layer 2 are defined as non-light-emitting regions 31, and the remaining pairs of quantum well structures 300 are defined as light-emitting regions 32. In other words, the light-emitting region 32 and the non-light-emitting region 31 are a plurality of pairs of quantum well structures 300, each pair of quantum well structures 300 each comprising a well layer 312, 314, 322, 324, 326 and a barrier layer 311, 313, 321 323, 325, 327, and the band gaps of the barrier layers 311, 313, 321, 323, 325, 327 are larger than the band gaps of the well layers 312, 314, 322, 324, 326, and each barrier layer 311 The thicknesses of 313, 321, 323, 325, and 327 are between 10 and 25 nm.

In summary, the nitride-based semiconductor light-emitting structure of the present invention comprises a quantum well structure 300 of a number of 4 to 15 pairs, which, as a whole, resembles a plurality of well layers 312, 314, 322, 324, 326 and a barrier layer 311, 313, 321, 323, 325, and 327 are repeatedly stacked and stacked with each other. Wherein, the thickness of the barrier layer 311, 313 of the quantum well structure 300 of the non-light-emitting region 31 is greater than the thickness of the barrier layer 321 , 323 , 325 , 327 of the quantum well structure 300 of the plurality of light-emitting regions 31 5 to 10 Nano. At the same time, the thickness of the barrier layers 311 and 313 of the plurality of pairs of quantum well structures 300 of the non-light-emitting region 31 is between 15 and 25 nm, preferably between 18 and 23. Between the rice. Moreover, the thickness of the barrier layers 321 , 323 , 325 , 327 of the plurality of pairs of quantum well structures 300 of the light-emitting region 32 is between 10 and 20 nm, preferably between 11 and 16 nm. . In summary, the nitride-based semiconductor active layer 3 of the present invention comprises the light-emitting region 32 and the non-light-emitting region 31. Since the barrier layers 311 and 313 of the non-light-emitting region 31 are thick, the excess stress generated in the epitaxial process can be effectively reduced. .

More specifically, both the illuminating region 32 and the non-emissive region 31 comprise at least two pairs of quantum well structures 300. The components of the well layers 312, 314, 322, 324, and 326 of the light-emitting region 32 and the non-light-emitting region 31 are indium gallium nitride (composition chemical formula: Ga _Y In _Z N, 0≦Y, Z≦1, Y+ Z=1), and the composition of the barrier layers 311, 313, 321, 323, 325, and 327 is GaN. However, the difference between the light-emitting region 32 and the non-light-emitting region 31 is not only the thickness of the barrier layers 311, 313, 321, 323, 325, 327, but the well layers 312, 314 of the non-light-emitting region 31 are not. Doping ions. As a result, electrons and holes are not easily recombined in the non-light-emitting region 31, and most of the electrons and holes are concentrated in the light-emitting region 32, and the light is released in the photon mode to generate light, thereby effectively improving the luminous efficiency.

Continuing to refer to FIG. 2, the nitride-based semiconductor light-emitting structure of the present invention further includes a substrate 1, a buffer layer 6, and an undoped nitride-based semiconductor layer 7. Wherein, the buffer layer 6 is formed on the surface of the substrate 1, while the undoped nitride-based semiconductor layer 7 is formed on the buffer layer 6, and finally the N-type is sequentially formed on the undoped nitride-based semiconductor layer 7. Nitride-based semiconductor layer 2, nitride-based semiconductor active Layer 3 and P-type nitride-based semiconductor layer 4. It is worthwhile to note that the buffer layer 6 can buffer the lattice difference between the substrate 1 and the semiconductor layer, so that the effect of epitaxy can be improved.

In summary, the embodiments of the present invention are not limited to the embodiments of the present invention, and are not intended to limit the present invention. Any equivalent modifications or alterations made without departing from the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1‧‧‧Substrate

2‧‧‧N type nitride semiconductor layer

3‧‧‧ nitride semiconductor active layer

300‧‧‧Quantum well structure

31‧‧‧Non-light-emitting area

32‧‧‧Lighting area

312, 314, 322, 324, 326‧‧ ‧ well layers

311, 313, 321, 323, 325, 327‧‧ ‧ barrier layer

4‧‧‧P type nitride semiconductor layer

5‧‧‧Electrode

6‧‧‧ buffer layer

7‧‧‧Undoped nitride-based semiconductor layer

Fig. 1 is a schematic view showing a first embodiment of a nitride-based semiconductor light-emitting structure of the present invention.

Fig. 2 is a schematic view showing a second embodiment of the nitride-based semiconductor light-emitting structure of the present invention.

2‧‧‧N type nitride semiconductor layer

3‧‧‧ nitride semiconductor active layer

300‧‧‧Quantum well structure

31‧‧‧Non-light-emitting area

32‧‧‧Lighting area

312, 314, 322, 324, 326‧‧ ‧ well layers

311, 313, 321, 323, 325, 327‧‧ ‧ barrier layer

4‧‧‧P type nitride semiconductor layer

Claims (8)

A nitride-based semiconductor light-emitting structure comprising: a P-type nitride-based semiconductor layer; an N-type nitride-based semiconductor layer; and a nitride-based semiconductor active layer formed on the P-type nitride-based semiconductor layer and Between the N-type nitride-based semiconductor layers, the nitride-based semiconductor active layer includes a plurality of pairs of quantum well structures, wherein the complex pair has at least 4 pairs of quantum well structures and is suitable for a dominant wavelength of 500 to 540 nm. Between the meters, and each of the plurality of quantum well structures comprises a well layer and a barrier layer, the barrier layer thickness being between 10 and 25 nanometers, wherein the complex number is close to the quantum well structure At least two pairs of the N-type nitride-based semiconductor layer are a non-emission region, and the remaining plurality of pairs of quantum well structures are a light-emitting region, the well layer of the non-light-emitting region is not doped with ions, and the complex pair of the non-light-emitting regions The thickness of the barrier layer of the quantum well structure is greater than the thickness of the complex layer of the light-emitting region to the thickness of the barrier layer of the quantum well structure of 5 to 10 nm. The nitride-based semiconductor light-emitting structure of claim 1, wherein the complex layer of the light-emitting region has a thickness of the barrier layer of the quantum well structure of 10 to 20 nm. The nitride-based semiconductor light-emitting structure of claim 2, wherein the complex layer of the light-emitting region has a thickness of the barrier layer of the quantum well structure of 11 to 16 nm. The nitride-based semiconductor light-emitting structure of claim 1, wherein the plurality of non-light-emitting regions have a thickness of the barrier layer of the quantum well structure of 15 to 25 nm. The nitride-based semiconductor light-emitting structure of claim 4, wherein the plurality of non-light-emitting regions have a thickness of the barrier layer of the quantum well structure of 18 to 23 nm. The nitride-based semiconductor light-emitting structure according to claim 1, wherein the N-type nitride-based semiconductor layer, the P-type nitride-based semiconductor layer, and the nitride-based semiconductor active layer do not contain aluminum. The nitride-based semiconductor light-emitting structure according to claim 1, further comprising a substrate and a buffer layer, wherein the buffer layer is formed on the substrate body, and the N-type nitride-based semiconductor layer is formed. On the buffer layer body. The nitride-based semiconductor light-emitting structure according to claim 7, further comprising an undoped nitride-based semiconductor layer between the buffer layer and the N-type nitride-based semiconductor layer.