LED epitaxial wafer and preparation method thereof, LED chip

Abstract

The present invention provides an LED epitaxial wafer and a preparation method thereof, and an LED chip, which belong to the field of semiconductor devices. The LED epitaxial wafer comprises an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer. The contact extension layer is a periodically overlapping structure, comprising an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence. The N-type GaN layer is an Si-doped N-type doped layer, the P-type GaN layer is an Mg-doped P-type doped layer, and the Si doping concentration in the N-type GaN layer is 1×10 17 cm ‑3 ‑1×10 18 cm ‑3 The doping concentration of Mg in the P-type GaN layer is 1×10 20 cm ‑3 ‑1×10 21 cm ‑3， In a single cycle, the thickness of the N-type GaN layer, the thickness of the N-type GaN layer and the thickness of the N-type GaN layer are all 0.5nm-2nm. The LED epitaxial wafer in the present invention solves the problem of poor light efficiency of the LED epitaxial wafer in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor devices, and in particular to an LED epitaxial wafer and its preparation, and an LED chip. Background Art

[0002] LED chip is a semiconductor electronic component that can emit light. It has the characteristics of small size, high brightness and low energy consumption. It is widely used in lighting and other fields. LED chip is obtained by splitting LED epitaxial wafer. LED epitaxial wafer is a solid light source, which is a light-emitting device made of semiconductor PN junction. When the forward current is turned on, the minority carriers (i.e. electrons) and majority carriers (i.e. holes) in the semiconductor recombine, and the released energy is emitted in the form of photons or part of it in the form of photons. LED epitaxial wafer lighting has significant advantages such as high efficiency, energy saving, environmental protection and long service life. It has been widely used in various aspects such as street lights, display screens, indoor lighting and car lights. Considering that the light effect is the most important measure of the competitiveness of LED epitaxial wafers, how to improve the light effect of LED epitaxial wafers on the basis of existing technology is an eternal topic to increase the competitiveness of LED epitaxial wafers.

[0003] At present, materials such as sapphire, silicon or silicon carbide are often used as substrates. With the continuous increase in the application fields, LED chips are not only concerned with brightness, but also with light efficiency. The operating voltage is a very important parameter affecting the light efficiency. Therefore, reducing the operating voltage of LED chips has become a key technical bottleneck. However, the current in the existing epitaxial wafers flows vertically, resulting in the problem of excessive current concentration affecting the operating voltage, which leads to excessively high operating voltage in the LED chip, affecting the light efficiency of the epitaxial wafer. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide an LED epitaxial wafer and a preparation method thereof, and an LED chip, so as to solve the problem of poor light efficiency of LED epitaxial wafers in the prior art.

[0005] The present invention provides an LED epitaxial wafer, comprising an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer, wherein the contact extension layer is a periodically overlapping structure, comprising an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence, the N-type GaN layer is a Si-doped N-type doped layer, and the P-type GaN layer is a Mg-doped P-type doped layer.

[0006] The present invention provides a contact extension layer on the P-type semiconductor layer, and realizes the effects of current expansion and ohmic contact through the contact extension layer, thereby ensuring the lateral expansion of the current on the epitaxial wafer, improving the light efficiency of the epitaxial wafer, and ensuring that the current can flow into and out of the epitaxial wafer smoothly. Specifically, the contact extension layer includes an N-type GaN layer, a first non-doped GaN layer and a P-type GaN layer, wherein the N-type doped GaN layer generates electrons, and the P-type doped GaN layer generates holes, which will be compounded and depleted in the non-doped GaN layer when powered on, slowing down the vertical travel of the current to a certain extent, so that the current expands laterally. The improvement of current expansion can improve the light distribution of the chip, making the light uniform while reducing the operating voltage and improving the light efficiency. The N-type GaN layer, the first non-doped GaN layer and the P-type GaN layer constitute a PN junction structure, that is, a PN junction is realized in the current expansion layer, so that the effect of ohmic contact is also achieved through the distribution of each layer, ensuring that the current can flow into and out of the epitaxial wafer smoothly. Therefore, the present invention solves the problem of poor light efficiency of LED epitaxial wafers in the prior art.

[0007] Preferably, within a single period of the contact extension layer, the thickness of the N-type GaN layer, the first undoped GaN layer and the thickness of the P-type GaN layer are all 0.5 nm-2 nm.

[0008] Preferably, the doping concentration of Si in the N-type GaN layer is 1×10 17 cm -3 -1×10 18 cm -3 The doping concentration of Mg in the P-type GaN layer is 1×10 20 cm -3 -1×10 21 cm -3 .

[0009] Preferably, the number of periods of the contact extension layer is 1-5.

[0010] Preferably, the LED epitaxial wafer further comprises a substrate, and an AlN layer, a buffer layer, a three-dimensional GaN layer and a second undoped GaN layer sequentially stacked on the substrate;

[0011] The N-type semiconductor layer, the stress release layer, the light-emitting layer, the electron blocking layer, the P-type semiconductor layer and the contact extension layer are sequentially stacked on the second non-doped GaN layer.

[0012] The present invention also provides a method for preparing an LED epitaxial wafer, the method comprising:

[0013] Provide semi-finished epitaxial wafers;

[0014] sequentially growing an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer on the semi-finished epitaxial wafer;

[0015] The contact extension layer is a periodically overlapping structure, including an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence, the N-type GaN layer is a Si-doped N-type doped layer, and the P-type GaN layer is a Mg-doped P-type doped layer.

[0016] Preferably, the step of sequentially growing an N-type semiconductor layer, a stress release layer and a light-emitting layer on the semi-finished epitaxial wafer comprises:

[0017] The step of sequentially growing an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer on the semi-finished epitaxial wafer comprises:

[0018] The semi-finished epitaxial wafer is placed in an MOCVD device, and an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer are sequentially grown on the semi-finished epitaxial wafer.

[0019] When growing the contact extension layer, the growth temperature is 900°C-1000°C, the MO source is TEGa, the introduced gases are N2, H2 and NH3, NH3 is used as the reaction gas, N2 and H2 are used as the carrier gas, and the growth pressure is 100torr-300torr.

[0020] Preferably, the number of periods of the contact extension layer is 1-5, and within a single period, the thicknesses of the N-type GaN layer, the first undoped GaN layer and the P-type GaN layer are all 0.5 nm-2 nm.

[0021] Preferably, when growing the N-type GaN layer in the contact extension layer, SiH4 source is used for N-type doping, and the doping concentration is 1×10 17 cm -3 -1×10 18 cm -3 When growing the P-type GaN layer in the contact extension layer, a Cp2Mg source is used for P-type doping, and the doping concentration is 1×10 20 cm -3 -1×10 21 cm -3 .

[0022] The present invention also provides an LED chip comprising the LED epitaxial wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1Schematic diagram of the structure of the light-emitting layer in the LED epitaxial wafer in one embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the structure of an LED epitaxial wafer in one embodiment of the present invention;

[0025] Figure 3 is a flow chart of a method for preparing an LED epitaxial wafer in one embodiment of the present invention;

[0026] Description of main component symbols:

[0027] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0029] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] like Figure 1 to Figure 2 As shown, the present invention discloses a partial structural schematic diagram of an LED epitaxial wafer, which includes a substrate 10 and an AlN layer 20, a buffer layer 30, a three-dimensional GaN layer 40, a second undoped GaN layer 50, an N-type semiconductor layer 60, a stress release layer 70, a light-emitting layer 80, an electron blocking layer 90, a P-type semiconductor layer 100 and a contact extension layer 110, which are sequentially arranged on the substrate 10.

[0032] In the present embodiment, the substrate 10 may be a sapphire substrate, a silicon substrate or a silicon carbide substrate, etc. Specifically, the thickness of the AlN layer 20 is 10nm-30nm, and exemplarily, the thickness of the AlN layer 20 is 10nm, 15nm, 20nm, 25nm or 30nm, but not limited thereto; the thickness of the buffer layer 30 is 15nm-35nm, and exemplarily, the thickness of the buffer layer 30 is 15nm, 20nm, 25nm, 30nm or 35nm, but not limited thereto; the thickness of the three-dimensional GaN layer 40 is 500nm -2000nm, exemplarily, the thickness of the three-dimensional GaN layer 40 is 500nm, 900nm, 1300nm, 1800nm ​​or 2000nm, but not limited thereto; the thickness of the second undoped GaN layer 50 is 800nm-1200nm, exemplarily, the thickness of the second undoped GaN layer 50 is 800nm, 900nm, 1000nm, 1100nm or 1200nm, but not limited thereto; the thickness of the N-type semiconductor layer 60 is 1000nm-3000nm, exemplarily, N The thickness of the semiconductor layer 60 is 1000nm, 1500nm, 2000nm, 2500nm or 3000nm, but is not limited thereto. The stress release layer 70 may be a periodic structure in which an InGaN layer and a GaN layer are alternately grown. The light emitting layer 80 may be a periodic structure in which an InGaN layer and a GaN layer are alternately grown. The thickness of the InGaN layer in the light emitting layer 80 is 2nm-4nm. For example, the thickness of the InGaN layer in the light emitting layer 80 is 2nm, 2.5nm, 3nm, 3.5nm or 4nm, but not limited thereto, the thickness of the GaN layer in the light-emitting layer 80 is 8nm-12nm, and exemplarily, the thickness of the GaN layer in the light-emitting layer 80 is 8nm, 9nm, 10nm, 11nm or 12nm, but not limited thereto, the electron blocking layer 90 can be a periodic structure in which AlGaN layers and GaN layers grow alternately, and the thickness of the electron blocking layer 90 is 10nm-60nm, and exemplarily, the thickness of the electron blocking layer 90 is 10nm, 25nm, 40nm, 50nm or 60nm, but not limited thereto. The thickness of the P-type semiconductor layer 100 is 5nm-100nm, and exemplarily, the thickness of the P-type semiconductor layer 100 is 5nm, 30nm, 60nm, 90nm or 100nm, but not limited thereto.

[0033] In this embodiment, the contact extension layer 110 is a periodic overlapping structure, including an N-type GaN layer 111, a first undoped GaN layer 112 and a P-type GaN layer 113 stacked in sequence, the N-type GaN layer 111 is an N-type doped layer using a SiH4 source, and the P-type GaN layer 113 is a P-type doped layer using a Cp2Mg source. It can be understood that by arranging the contact extension layer 110 on the P-type semiconductor layer 100, the contact extension layer 110 can achieve the effects of current expansion and ohmic contact, thereby ensuring the lateral expansion of the current on the epitaxial wafer, improving the optical efficiency of the epitaxial wafer, and ensuring that the current can flow smoothly into and out of the epitaxial wafer. Specifically, the contact extension layer 110 includes an N-type GaN layer 111, a first non-doped GaN layer 112, and a P-type GaN layer 113, wherein the N-type doped GaN layer generates electrons, and the P-type doped GaN layer generates holes, which will be recombined and depleted in the non-doped GaN layer when powered on, slowing down the vertical travel of the current to a certain extent, so that the current expands laterally. The improvement of the current expansion can improve the light distribution of the chip, making the light uniform while reducing the operating voltage and improving the light efficiency. The N-type GaN layer 111, the first non-doped GaN layer 112, and the P-type GaN layer 113 form a PN junction structure, that is, a PN junction is realized in the current expansion layer, so that the ohmic contact effect is also achieved through the distribution of each layer, ensuring that the current can flow smoothly into and out of the epitaxial wafer. Therefore, the present invention solves the problem of poor light efficiency of LED epitaxial wafers in the prior art.

[0034] In addition, the thickness of the contact extension layer 110 and the concentration of dopants in the current have a significant influence on the current spreading effect, that is, the thickness of the N-type GaN layer 111, the first undoped GaN layer 112 and the P-type GaN layer 113, the number of periods of the contact extension layer 110, and the concentration of dopants in the N-type GaN layer 111 and the P-type GaN layer 113 have a direct influence on the current spreading effect of the contact extension layer 110. In this embodiment, the number of periods of the contact extension layer 110 is 1-5. Exemplarily, the number of periods of the contact extension layer 110 is 1, 2, 3, 4 or 5, but not limited thereto. In a single period, the thickness of the N-type GaN layer 111 in the contact extension layer 110 is 0.5nm-2nm. Exemplarily, the thickness of the N-type GaN layer 111 in the contact extension layer 110 is 0.5nm, 0.7nm, 1nm, 1.4nm, 1.8nm or 2nm, etc., but not limited thereto. The thickness of the first undoped GaN layer 112 in the contact extension layer 110 is 0.5nm-2nm , exemplarily, the thickness of the first non-doped GaN layer 112 in the contact extension layer 110 is 0.5 nm, 0.8 nm, 1 nm, 1.3 nm, 1.7 nm or 2 nm, etc., but not limited thereto, the thickness of the P-type GaN layer 113 in the contact extension layer 110 is 0.5 nm-2 nm, exemplarily, the thickness of the P-type GaN layer 113 in the contact extension layer 110 is 0.5 nm, 0.9 nm, 1 nm, 1.6 nm, 1.9 nm or 2 nm, etc., but not limited thereto, the doping concentration of Si in the N-type GaN layer 111 in the contact extension layer 110 is 1×10 17 cm -3 -1×10 18 cm -3 For example, the doping concentration of Si in the N-type GaN layer 111 in the contact extension layer 110 is 1×10 17 cm -3 , 3×10 17 cm -3 , 5×10 17 cm -3 ,7×10 17 cm -3 ,9×10 17 cm -3 or 1×10 18 cm -3 , but not limited thereto, the Mg doping concentration in the P-type GaN layer 113 in the contact extension layer 110 is 1×10 20 cm -3 -1×10 21 cm -3 For example, the doping concentration of Mg in the P-type GaN layer 113 in the contact extension layer 110 is 1×10 20 cm -3 , 2×1020 cm -3 , 4×10 20 cm -3 , 6×10 20 cm -3 , 8×10 20 cm -3 or 1×10 21 cm -3 .

[0035] Accordingly, refer to Figure 3 The present invention also discloses a method for preparing an LED epitaxial wafer, which is used to prepare the above-mentioned LED epitaxial wafer, wherein the preparation method comprises the following steps:

[0036] S100: providing a substrate;

[0037] Preferably, the substrate may be a sapphire substrate.

[0038] S200 sequentially grows an AlN layer, a buffer layer, a three-dimensional GaN layer, a second undoped GaN layer, an N-type semiconductor layer, a stress release layer and a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer on the substrate along the epitaxial growth direction.

[0039] Specifically, S200 includes:

[0040] S201: placing the substrate in a PVD device to grow an AlN layer;

[0041] Specifically, the thickness of the AlN layer is 10 nm to 30 nm.

[0042] S202: growing a buffer layer on the AlN layer;

[0043] Specifically, after the buffer layer is grown, the epitaxial wafer is transferred to a MOCVD device to grow a buffer layer on the AlN layer, and the thickness of the buffer layer is 15 nm-35 nm.

[0044] S203: growing a three-dimensional GaN layer on the buffer layer;

[0045] Specifically, in an MOCVD device, a three-dimensional GaN layer is grown on the buffer layer, and the thickness of the three-dimensional GaN layer is 500nm-2000nm.

[0046] S204: growing a non-doped GaN layer on the three-dimensional GaN layer;

[0047] Specifically, in an MOCVD device, a non-doped GaN layer is grown on the three-dimensional GaN layer, and the thickness of the non-doped GaN layer is 800nm-1200nm.

[0048] S205: growing an N-type semiconductor layer on the non-doped GaN layer;

[0049] Specifically, an N-type semiconductor layer is grown on a non-doped GaN layer in an MOCVD device, the thickness of the N-type semiconductor layer is 1000nm-3000nm, and the N-type semiconductor layer is an N-type doped GaN layer.

[0050] S206: growing a stress release layer on the N-type semiconductor layer;

[0051] Specifically, a stress release layer is grown on the N-type semiconductor layer in an MOCVD device, and the stress release layer is a periodic structure in which InGaN layers and GaN layers are grown alternately.

[0052] S207: growing a light-emitting layer on the stress release layer;

[0053] Specifically, a light-emitting layer is grown on the stress release layer in an MOCVD device. The light-emitting layer is a periodic structure in which InGaN layers and GaN layers grow alternately. The thickness of the InGaN layer can be 2nm-4nm, the thickness of the GaN layer can be 8nm-12nm, and the number of periods is 6-14.

[0054] S208: growing an electron blocking layer on the light-emitting layer;

[0055] Specifically, an electron blocking layer is grown on the light-emitting layer in an MOCVD device. The electron blocking layer is a periodic structure in which AlGaN layers and GaN layers are grown alternately, and has a thickness of 10 nm to 60 nm.

[0056] S209: growing a P-type semiconductor layer on the electron blocking layer;

[0057] Specifically, a P-type semiconductor layer is grown on the electron blocking layer in an MOCVD device, and the P-type semiconductor layer is a P-type doped GaN layer with a thickness of 5nm-100nm.

[0058] S210: growing a contact extension layer on the P-type semiconductor layer;

[0059] Specifically, the contact extension layer is a periodic overlapping structure, including an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence, the N-type GaN layer is an N-type doped layer using SiH4, the P-type GaN layer is a P-type doped layer using Cp2Mg, the number of periods of the contact extension layer is 1-5, and within a single period, the thicknesses of the N-type GaN layer, the N-type GaN layer and the N-type GaN layer are all 0.5nm-2nm;

[0060] When growing the contact extension layer, the growth temperature is 900° C.-1000° C., the MO source is TEGa, the introduced gases are N2, H2 and NH3, NH3 is used as the reaction gas, N2 and H2 are used as the carrier gas, and the growth pressure is 100torr-300torr;

[0061] When growing the N-type GaN layer in the contact extension layer, SiH4 source is used for N-type doping with a doping concentration of 1×10 17 cm -3 -1×10 18 cm -3 When growing the P-type GaN layer in the contact extension layer, Cp2Mg source is used for P-type doping with a doping concentration of 1×10 20 cm -3 -1×10 21 cm -3 .

[0062] The present invention is further described below with specific embodiments:

[0063] Embodiment 1

[0064] The present embodiment provides an LED epitaxial wafer, which also includes a substrate and an AlN layer, a buffer layer, a three-dimensional GaN layer, an undoped GaN layer, an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer and a P-type semiconductor layer sequentially arranged on the substrate.

[0065] In this embodiment, the substrate is a GaAs substrate, the thickness of the AlN layer is 20 nm, the thickness of the buffer layer is 25 nm, the thickness of the three-dimensional GaN layer is 1200 nm, the thickness of the undoped GaN layer is 1000 nm, the N-type semiconductor layer is an N-type doped GaN layer, the thickness of the N-type semiconductor layer is 2000 nm, the stress release layer is a periodic structure in which an InGaN layer and a GaN layer are alternately grown, the light-emitting layer is a periodic structure in which an InGaN layer and a GaN layer are alternately grown, the number of periods of the light-emitting layer is 10, the thickness of the InGaN layer in the light-emitting layer is 3 nm, the thickness of the GaN layer in the light-emitting layer is 10 nm, and the electron blocking The layer is a periodic structure in which AlGaN layers and GaN layers are alternately grown, with a thickness of 40nm, the P-type semiconductor layer is a P-type doped GaN layer with a thickness of 60nm, and the contact extension layer is a periodic overlapping structure, including an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence, the N-type GaN layer is an N-type doped layer using SiH4, and the P-type GaN layer is a P-type doped layer using Cp2Mg. The number of periods of the contact extension layer is 3. In a single period, the thicknesses of the N-type GaN layer, the N-type GaN layer and the N-type GaN layer are all 1nm, and the doping concentration of Si in the N-type GaN layer of the contact extension layer is 5×10 17 cm -3The Mg doping concentration in the P-type GaN layer of the contact extension layer is 5×10 20 cm -3 .

[0066] The method for preparing the LED epitaxial wafer in this embodiment comprises the following steps:

[0067] (1): Providing a substrate;

[0068] In this embodiment, the substrate is a GaAs substrate.

[0069] (2): growing an AlN layer, a buffer layer, a three-dimensional GaN layer, an undoped GaN layer, the N-type semiconductor layer, the stress release layer and the light-emitting layer, an electron blocking layer and a P-type semiconductor layer in sequence along the epitaxial growth direction on the substrate;

[0070] Specifically, step (2) includes:

[0071] S201: placing the substrate in a PVD device to grow an AlN layer;

[0072] Specifically, the thickness of the AlN layer is 20 nm.

[0073] growing a buffer layer on the AlN layer;

[0074] Specifically, after the buffer layer is grown, the epitaxial wafer is transferred to a MOCVD device to grow a buffer layer on the AlN layer. The thickness of the buffer layer is 25 nm.

[0075] Growing a three-dimensional GaN layer on the buffer layer;

[0076] Specifically, in an MOCVD device, a three-dimensional GaN layer is grown on the buffer layer, and the thickness of the three-dimensional GaN layer is 1200 nm.

[0077] Growing a non-doped GaN layer on the three-dimensional GaN layer;

[0078] Specifically, in an MOCVD device, a non-doped GaN layer is grown on the three-dimensional GaN layer, and the thickness of the non-doped GaN layer is 1000 nm.

[0079] growing an N-type semiconductor layer on the non-doped GaN layer;

[0080] Specifically, an N-type semiconductor layer is grown on the non-doped GaN layer in an MOCVD device, the thickness of the N-type semiconductor layer is 2000 nm, and the N-type semiconductor layer is an N-type doped GaN layer.

[0081] growing a stress relief layer on the N-type semiconductor layer;

[0082] Specifically, a stress release layer is grown on the N-type semiconductor layer in an MOCVD device, and the stress release layer is a periodic structure in which InGaN layers and GaN layers are grown alternately.

[0083] growing a light-emitting layer on the stress release layer;

[0084] Specifically, a light-emitting layer is grown on the stress release layer in an MOCVD device. The light-emitting layer is a periodic structure in which InGaN layers and GaN layers are grown alternately. The thickness of the InGaN layer can be 3 nm, the thickness of the GaN layer can be 10 nm, and the number of periods is 10.

[0085] growing an electron blocking layer on the light-emitting layer;

[0086] Specifically, an electron blocking layer is grown on the light-emitting layer in an MOCVD device. The electron blocking layer is a periodic structure in which AlGaN layers and GaN layers are grown alternately, and has a thickness of 40 nm.

[0087] growing a P-type semiconductor layer on the electron blocking layer;

[0088] Specifically, a P-type semiconductor layer is grown on the electron blocking layer in an MOCVD device, wherein the P-type semiconductor layer is a P-type doped GaN layer having a thickness of 60 nm;

[0089] growing a contact extension layer on the P-type semiconductor layer;

[0090] Specifically, a contact extension layer is grown on a P-type semiconductor layer in an MOCVD device. The contact extension layer is a periodically overlapping structure, including an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence. The N-type GaN layer is an N-type doped layer using SiH4, and the P-type GaN layer is a P-type doped layer using Cp2Mg. The number of periods of the contact extension layer is 3. In a single period, the thicknesses of the N-type GaN layer, the N-type GaN layer and the N-type GaN layer are all 1 nm. When growing the contact extension layer, the growth temperature is 930°C, the MO source is TEGa, the gases introduced are N2, H2 and NH3, NH3 is used as a reaction gas, N2 and H2 are used as carrier gases, and the growth pressure is 200 torr. When growing the N-type GaN layer in the contact extension layer, SiH4 source is used for N-type doping, and the doping concentration is 5×10 17 cm -3 When growing the P-type GaN layer in the contact extension layer, Cp2Mg source is used for P-type doping with a doping concentration of 5×10 20 cm -3 .

[0091] Embodiment 2

[0092] This embodiment also provides an LED epitaxial wafer. The difference from the first embodiment is that the Si doping concentration in the N-type GaN layer in the contact extension layer is 1×10 17 cm -3 .

[0093] Embodiment 3

[0094] This embodiment also provides an LED epitaxial wafer. The difference from the first embodiment is that the Si doping concentration in the N-type GaN layer in the contact extension layer is 1×10 18 cm -3 .

[0095] Embodiment 4

[0096] This embodiment also provides an LED epitaxial wafer, which is different from the first embodiment in that the Mg doping concentration in the P-type GaN layer of the contact extension layer is 1×10 20 cm -3 .

[0097] Embodiment 5

[0098] This embodiment also provides an LED epitaxial wafer, which is different from the first embodiment in that the Mg doping concentration in the P-type GaN layer of the contact extension layer is 1×10 21 cm -3 .

[0099] Embodiment 6

[0100] This embodiment also provides an LED epitaxial wafer, which differs from the first embodiment in that, in a single period, the thickness of the N-type GaN layer, the thickness of the N-type GaN layer and the thickness of the N-type GaN layer are all 0.3 nm.

[0101] Embodiment 7

[0102] This embodiment also provides an LED epitaxial wafer, which differs from the first embodiment in that, in a single period, the thickness of the N-type GaN layer, the thickness of the N-type GaN layer and the thickness of the N-type GaN layer are all 0.5 nm.

[0103] Embodiment 8

[0104] This embodiment also provides an LED epitaxial wafer, which differs from the first embodiment in that, in a single period, the thickness of the N-type GaN layer, the thickness of the N-type GaN layer and the thickness of the N-type GaN layer are all 1.5 nm.

[0105] Embodiment 9

[0106] This embodiment also provides an LED epitaxial wafer, which is different from the first embodiment in that, in a single period, the thickness of the N-type GaN layer, the thickness of the N-type GaN layer and the thickness of the N-type GaN layer are all 2 nm.

[0107] Embodiment 10

[0108] This embodiment also provides an LED epitaxial wafer, which differs from the first embodiment in that, in a single period, the thickness of the N-type GaN layer, the thickness of the N-type GaN layer and the thickness of the N-type GaN layer are all 2.5 nm.

[0109] Comparative Example 1

[0110] This comparative example provides an LED epitaxial wafer and a preparation method thereof, which is different from the first embodiment in that the thickness of the quantum well layer in the first light-emitting layer is consistent with the thickness of the quantum well layer in the second light-emitting layer.

[0111] The LED epitaxial wafers obtained in Examples 1 to 11 and Comparative Example 1 were used to prepare LED chips with a size of 22 mil*35 mil. The test current was 60 mA and the tests were carried out under the same conditions. The specific results are shown in Table 1:

[0112] Table 1

[0113]

[0114] It can be seen from Table 1 that the LED epitaxial wafer obtained by the method in the embodiment of the present invention is used to prepare an LED chip with a size of 22mil*35mil. Under the same test conditions, the LED chip prepared by the method in the first embodiment of the present invention has an effective improvement in luminous efficiency of 1.7% compared with the LED chip prepared by the traditional method in the first comparative example. At the same time, the working voltage of the LED chips prepared by the methods in other embodiments of the present invention is mostly lower than the working voltage of the LED chips prepared by the traditional method, and the luminous efficiency is also mostly higher than the luminous efficiency of the LED chips prepared by the traditional method. It can be seen from the above embodiments that the luminous efficiency of the chip is in a normal distribution corresponding relationship with the thickness of each layer in the contact layer, the Si doping concentration in the N-type GaN layer of the contact layer, and the Mg doping concentration in the P-type GaN layer of the contact layer, and there is an optimal value.

[0115] An embodiment of the present invention further provides an LED chip, comprising the above-mentioned LED epitaxial wafer.

[0116] In summary, the LED epitaxial wafer and its preparation method, and the LED chip in the embodiment of the present invention achieve the effects of current expansion and ohmic contact through the contact expansion layer, thereby ensuring the lateral expansion of the current on the epitaxial wafer, improving the light efficiency of the epitaxial wafer, and ensuring that the current can flow into and out of the epitaxial wafer smoothly. Specifically, the contact expansion layer includes an N-type GaN layer, a first non-doped GaN layer, and a P-type GaN layer, wherein the N-type doped GaN layer generates electrons, and the P-type doped GaN layer generates holes, which will be recombined and depleted in the undoped GaN layer when powered on, slowing down the vertical travel of the current to a certain extent, so that the current expands laterally. The improvement of current expansion can improve the luminous distribution of the chip, making the light uniform while reducing the operating voltage and improving the light efficiency. The N-type GaN layer, the first non-doped GaN layer, and the P-type GaN layer constitute a PN junction structure, that is, a PN junction is realized in the current expansion layer, so that the effect of ohmic contact is also achieved through the distribution of each layer, ensuring that the current can flow into and out of the epitaxial wafer smoothly. Therefore, the present invention solves the problem of poor light efficiency of LED epitaxial wafers in the prior art.

[0117] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0118] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An LED epitaxial wafer, characterized in that: It includes an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer, wherein the contact extension layer is a periodically overlapping structure, including an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence, wherein the N-type GaN layer is a Si-doped N-type doped layer, and the P-type GaN layer is a Mg-doped P-type doped layer; The doping concentration of Si in the N-type GaN layer is 1×10 17 cm -3 -1×10 18 cm -3 The doping concentration of Mg in the P-type GaN layer is 1×10 20 cm -3 -1×10 21 cm -3 .

2. The LED epitaxial wafer according to claim 1, characterized in that: In a single period of the contact extension layer, the thickness of the N-type GaN layer, the first undoped GaN layer and the thickness of the P-type GaN layer are all 0.5 nm-2 nm.

3. The LED epitaxial wafer according to claim 1, characterized in that: The number of cycles of the contact extension layer is 1-5.

4. The LED epitaxial wafer according to claim 1, characterized in that: The LED epitaxial wafer also includes a substrate, and an AlN layer, a buffer layer, a three-dimensional GaN layer and a second non-doped GaN layer sequentially stacked on the substrate; The N-type semiconductor layer, the stress release layer, the light-emitting layer, the electron blocking layer, the P-type semiconductor layer and the contact extension layer are sequentially stacked on the second non-doped GaN layer.

5. A method for preparing an LED epitaxial wafer, characterized in that: Used to prepare the LED epitaxial wafer according to any one of claims 1 to 4, the preparation method comprising: Provide semi-finished epitaxial wafers; sequentially growing an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer on the semi-finished epitaxial wafer; The contact extension layer is a periodically overlapping structure, including an N-type GaN layer, a first undoped GaN layer and a P-type GaN layer stacked in sequence, the N-type GaN layer is a Si-doped N-type doped layer, and the P-type GaN layer is a Mg-doped P-type doped layer.

6. The method for preparing an LED epitaxial wafer according to claim 5, characterized in that: The step of sequentially growing an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer on the semi-finished epitaxial wafer comprises: The semi-finished epitaxial wafer is placed in an MOCVD device, and an N-type semiconductor layer, a stress release layer, a light-emitting layer, an electron blocking layer, a P-type semiconductor layer and a contact extension layer are sequentially grown on the semi-finished epitaxial wafer. When growing the contact extension layer, the growth temperature is 900°C-1000°C, the MO source is TEGa, the introduced gases are N2, H2 and NH3, NH3 is used as the reaction gas, N2 and H2 are used as the carrier gas, and the growth pressure is 100torr-300torr.

7. The method for preparing an LED epitaxial wafer according to claim 6, characterized in that: The number of periods of the contact extension layer is 1-5, and within a single period, the thicknesses of the N-type GaN layer, the first undoped GaN layer, and the P-type GaN layer are all 0.5nm-2nm.

8. The method for preparing an LED epitaxial wafer according to claim 7, characterized in that: When growing the N-type GaN layer in the contact extension layer, SiH4 source is used for N-type doping, and the doping concentration is 1×10 17 cm -3 -1×10 18 cm -3 When growing the P-type GaN layer in the contact extension layer, a Cp2Mg source is used for P-type doping, and the doping concentration is 1×10 20 cm -3 -1×10 21 cm -3 .

9. An LED chip, characterized in that: The LED chip comprises the LED epitaxial wafer as claimed in any one of claims 1 to 4.

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