GaN single-chip white light emitting tube with p-NiO as cap layer and preparation method thereof

Abstract

A GaN single-chip white light emitting tube with p-NiO as the cap layer and a preparation method thereof, belonging to the field of semiconductor light emitting devices and their preparation technology. The device is composed of a substrate, a GaN buffer layer, an n-type Si-doped GaN electron injection layer, a multi-quantum well active light emitting layer, a p-type Mg-doped Al z Ga 1‑z The active light-emitting layer is composed of blue light Al y1 Ga 1‑y1 N carrier confinement layer, blue light multiple quantum well In x1 Ga 1‑x1 N material active light emitting layer, yellow light Al y2 Ga 1‑y2 N carrier confinement layer, yellow light multiple quantum well In x2 Ga 1‑x2 The present invention utilizes the characteristics of high hole concentration, wide band gap and low refractive index of p-NiO, so that the device has good hole injection and light and carrier confinement, reduces the influence of high temperature growth on the active light-emitting layer, and improves the device performance.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor light emitting devices and preparation thereof, and in particular relates to a single-chip white light emitting tube of GaN material system with p-NiO as a cap layer and no phosphor and a preparation method thereof. Background Art

[0002] At present, most of the white light emitting tubes (LEDs) used for lighting are made of GaN material blue light emitting tubes and yellow phosphors. However, such white light emitting tubes with blue light stimulating yellow phosphors have problems such as short phosphor life, high color temperature and low color rendering index. At the same time, the phosphors also have problems such as slow response and temperature instability. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned difficulty of GaN material-based white light emitting tubes, and to provide a GaN material-based single-chip white light emitting tube without phosphor using p-NiO as a cap layer (light confinement layer and hole injection layer) and a preparation method thereof by utilizing the wide bandgap, high hole concentration, low refractive index and low growth temperature of p-NiO. The hole concentration of the p-NiO cap layer prepared by the present invention can be as high as 10 18 ~10 20 / cm 3 The resistivity is very low, only 2 to 4Ω·cm (see Table 1). At the same time, the refractive index of NiO is almost the same as that of AlN, which can completely limit the light emitted by the active light-emitting layer of the InGaN material to improve the performance of the white light-emitting tube.

[0004] The technical solution of the present invention is:

[0005] The GaN single-chip white light emitting tube (see attached) designed by the present invention with p-NiO as the cap layer (light confinement layer and hole injection layer) Figure 1 , from bottom to top, a substrate 1, a GaN buffer layer 8 prepared on the substrate 1, an n-type Si-doped layer (the doping concentration of Si is in the range of 1×10 18 / cm 3 ~9.9×10 19 / cm 3 ) of the GaN electron injection layer 2, the mutually separate multi-quantum well active light-emitting layer 3 and the lower electrode 7 prepared on the GaN electron injection layer 2, and the p-type Mg-doped (Mg doping concentration range is 1×10 17 / cm 3 ~5×10 18 / cm 3 ) z Ga 1-z N electron confinement layer 4, Al z Ga 1-zThe substrate 1 is Al2O3 or Si crystal sheet; the cap layer (light confinement layer and hole injection layer) 5 is p-NiO, and the hole concentration is 1.0×10 18 / cm 3 ~9.9×10 20 / cm 3 ; The multi-quantum well active light-emitting layer 3 is composed of blue light Al y1 Ga 1-y1 N carrier confinement layer 3-2, blue light multiple quantum well In x1 Ga 1-x1 N material active light emitting layer 3-1, yellow light Al y2 Ga 1-y2 N carrier confinement layer 3-4, yellow light multiple quantum well In x2 Ga 1-x2 The N material active light-emitting layer 3-3 is composed of four parts.

[0006] Among them, blue light multi-quantum well In x1 Ga 1-x1 The N material active light emitting layer 3-1 is composed of a well layer In x11 Ga 1-x11 N and barrier layer In x12 Ga 1-x12 N alternately constituted, the number of pairs is 2 to 5; yellow light multiple quantum well In x2 Ga 1-x2 The N material active light emitting layer 3-3 is composed of a well layer In x21 Ga 1-x21 N and barrier layer In x22 Ga 1-x22 N is composed of alternating pairs, with the number of pairs ranging from 2 to 5;

[0007] The values ​​of x1 (x11, x12), y1, x2 (x21, x22), y2, and z are appropriately selected according to the bandgap width of the material. The value range of x11 for the blue light quantum well is 0.15-0.22, and the value of x12 for the barrier layer of the blue light quantum well is usually 0.1-0.22 smaller than x11; the value range of x21 for the yellow light quantum well is 0.30-0.36, and the value of x22 for the barrier layer of the yellow light quantum well is usually 0.1-0.30 smaller than x21; the value range of y1 and y2 is 0-0.2, and the value range of z is 0.1-0.4.

[0008] In order to further reduce the influence of heating on the active light-emitting layer when the electron confinement layer is epitaxially grown after the active light-emitting layer is prepared, and to simplify the process, the present invention designs a GaN single-chip white light-emitting tube (see attached) with p-NiO as a cap layer (light confinement layer and hole injection layer) and also as an electron confinement layer. Figure 2 , from bottom to top, a substrate 1, a GaN buffer layer 8 prepared on the substrate 1, and an n-type Si-doped layer (the doping concentration of Si is in the range of 1×10 18 / cm 3 ~9.9×10 19 / cm 3 ) of a GaN electron injection layer 2, a mutually independent multi-quantum well active light-emitting layer 3 and a lower electrode 7 prepared on the GaN electron injection layer 2, a cap layer (light confinement layer and hole injection layer) 5 prepared on the active light-emitting layer 3, and an upper electrode 6 prepared on the cap layer 5, characterized in that: the substrate 1 is an Al2O3 or Si crystal sheet; the cap layer (light confinement layer and hole injection layer) 5 is p-NiO, and the hole concentration is 1.0×10 18 / cm 3 ~9.9×10 20 / cm 3 ; The multi-quantum well active light-emitting layer 3 is composed of blue light Al y1 Ga 1-y1 N carrier confinement layer 3-2, blue light multiple quantum well In x1 Ga 1-x1 N material active light emitting layer 3-1, yellow light Al y2 Ga 1-y2 N carrier confinement layer 3-4, yellow light multiple quantum well In x2 Ga 1-x2 The N material active light-emitting layer 3-3 is composed of four parts.

[0009] Among them, blue light multi-quantum well In x1 Ga 1-x1 The N material active light emitting layer 3-1 is composed of a well layer In x11 Ga 1-x11 N and barrier layer In x12 Ga 1-x12 N alternately constituted, the number of pairs is 2 to 5; yellow light multiple quantum well In x2 Ga 1-x2 The N material active light emitting layer 3-3 is composed of a well layer In x21 Ga 1-x21 N and barrier layer In x22 Ga 1-x22 N is composed of alternating pairs, with the number of pairs ranging from 2 to 5;

[0010] The values ​​of x1 (x11, x12), y1, x2 (x21, x22), y2, and z are appropriately selected according to the bandgap width of the material. The value range of x11 for the blue light quantum well is 0.15-0.22, and the value of x12 for the barrier layer of the blue light quantum well is usually 0.1-0.22 smaller than x11; the value range of x21 for the yellow light quantum well is 0.30-0.36, and the value of x22 for the barrier layer of the yellow light quantum well is usually 0.1-0.30 smaller than x21; the value range of y1 and y2 is 0-0.2, and the value range of z is 0.1-0.4.

[0011] Preparation method: The substrate 1 is usually made of sapphire (Al2O3) or silicon (Si) single crystal materials, and can also be made of silicon carbide (SiC) and gallium nitride (GaN) single crystal materials, but the cost is slightly higher; the GaN buffer layer 8, GaN electron injection layer 2, multi-quantum well active light-emitting layer 3 and Al2O3 of the GaN single-chip white light-emitting tube with p-NiO as the cap layer (light confinement layer and hole injection layer), z Ga 1-z The N electron confinement layer 4 can be prepared by epitaxial growth using a conventional MOCVD (metal organic chemical vapor deposition) process which is relatively mature at present. Currently, the MOCVD process for preparing p-NiO thin film materials is not mature yet, so the p-NiO cap layer 5 is prepared by magnetron sputtering. The material for preparing the upper electrode 6 can be a single metal or binary alloy material such as Au or Ti-Al, Ni-Au, Ti-Au, Zn-Au or Pt-Au, or a ternary alloy material such as Ti-Pt-Au, Ti-Al-Au or Ni-Pt-Au, and a quaternary alloy composite material of Ti-Al-Ni-Au. The preparation method can be thermal evaporation, electron beam evaporation or magnetron lasing. The material of the lower electrode 7 can also be a single metal or binary alloy material such as Au, Ni, Ni-Au, Ti-Au, Zn-Au or Pt-Au, or a ternary alloy such as Ti-Pt-Au, Ti-Ni-Au or Ni-Pt-Au, and a quaternary alloy material of Ti-Al-Ni-Au. The preparation method can be thermal evaporation, electron beam evaporation or magnetron lasing. The materials of the upper and lower electrodes are generally different.

[0012] The method for preparing a GaN single-chip white light emitting tube with p-NiO as a cap layer (light confinement layer and hole injection layer) of the present invention is characterized in that: a GaN buffer layer 8, a GaN electron injection layer 2, an active light emitting layer 3 and an Al z Ga 1-z The N electron confinement layer 4 is prepared by MOCVD, the p-NiO capping layer 5 is prepared by magnetron sputtering, and the upper electrode 6 and the lower electrode 7 can be prepared by thermal evaporation, electron beam evaporation or magnetron lasing.

[0013] The effects and benefits of the present invention are:

[0014] The active light-emitting layer of the GaN single-chip white light emitting tube with p-NiO as the cap layer (light confinement layer and hole injection layer) prepared by the present invention can emit yellow light and blue light at the same time to synthesize white light without using fluorescent powder. This overcomes the problems of short life of fluorescent powder, high color temperature, low color rendering index, slow response, temperature instability, etc. At the same time, the characteristics of p-NiO with high hole concentration, low resistivity, wide band gap, lower refractive index than AlGaN material, and very low growth temperature are utilized, so that the device can have good hole injection, good light confinement and carrier confinement, and can reduce the operating voltage of the device, reduce the influence of high-temperature growth of GaN cap layer on the quantum well active light-emitting layer, thereby improving the crystal quality of the yellow light quantum well light-emitting area, facilitating the synthesis of white light, and improving the device performance of the white light emitting tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 : Schematic diagram of the structure of a GaN single-chip white light emitting tube with p-NiO prepared in Example 1 as the cap layer (light confinement layer and hole injection layer).

[0016] Figure 2 : Schematic diagram of the structure of a GaN single-chip white light emitting tube in which the p-NiO prepared in Example 2 is used as the cap layer (light confinement layer and hole injection layer) and also as the electron confinement layer.

[0017] Figure 3 : The voltage-current characteristic curve of the GaN single-chip white light-emitting tube with p-NiO as the cap layer prepared in Example 1. The curve shows a good diode characteristic curve, which shows that this light-emitting tube has good pn junction characteristics, indicating that p-NiO has a good hole injection effect.

[0018] Figure 4 : The electric injection luminescence spectrum of the GaN single chip white light emitting tube with p-NiO as the cap layer prepared in Example 1. From the luminescence spectrum, it can be seen that the light emitting tube emits blue light and yellow light at the same time, which is white light to the naked eye.

[0019] Figure 5 , Example 2 prepared p-NiO as the cap layer (light confinement layer and hole injection layer) and also as the electron confinement layer of the GaN single-chip white light emitting tube at different current densities. Figure 4 , 5 It can be seen that this light-emitting tube has good light-emitting characteristics, which shows its feasibility.

[0020] Table 1: Hall test results of p-NiO thin film samples sputtered at different temperatures

[0021]

[0022] The names of the parts in the figure are: substrate 1, GaN electron injection layer 2, multi-quantum well active light-emitting layer 3, Al z Ga 1-z N electron confinement layer 4, cap layer (light confinement layer and hole injection layer) 5, upper electrode 6, lower electrode 7, buffer layer 8, blue light multi-quantum well In x1 Ga 1-x1 N material active light emitting layer 3-1, blue light Al y1 Ga 1-y1 N carrier confinement layer 3-2, yellow light multiple quantum well In x2 Ga 1-x2 N material active light emitting layer 3-3, yellow light Al y2 Ga 1-y2 N carrier confinement layer 3-4. DETAILED DESCRIPTION

[0023] The specific embodiments and implementation processes of the present invention are described in detail below in conjunction with the technical solutions and drawings.

[0024] Embodiment 1:

[0025] GaN single chip white light emitting tube with p-NiO as cap layer (light confinement layer and hole injection layer) is attached Figure 1 The preparation process is as follows: an Al2O3 crystal sheet is used as the substrate 1. Since the lattice mismatch between the Al2O3 crystal and the high-temperature grown GaN crystal is large, a 20nm thick undoped GaN buffer layer 8 is first grown on the substrate 1 using MOCVD at low temperature (550℃), and then a 2-micron thick n-type (Si-doped, carrier concentration 4×10 18 / cm 3 )GaN electron injection layer 2; then start growing an undoped multi-quantum well active light-emitting layer 3, the growth steps of the multi-quantum well active light-emitting layer 3 are: first grow blue light Al y1 Ga 1-y1 N carrier confinement layer 3-2, the Al content y1 value of the carrier confinement layer 3-2 is selected to be 0.05, the thickness is 10nm, and the growth temperature is 1010℃; then the blue light multi-quantum well In x1 Ga 1-x1 N material active light-emitting layer 3-1, blue light multi-quantum well In x1 Ga 1-x1 The N material active light emitting layer 3-1 is composed of a well layer In x11 Ga 1-x11 N and barrier layer In x12 Ga 1-x12N alternately, where the In component x11 of the quantum well layer is 0.21, the corresponding emission wavelength is about 450nm, the thickness is 3nm, and the growth temperature is 780℃; the In component x12 of the quantum well barrier layer is 0, the thickness is 5nm, and the growth temperature is 855℃. The logarithm of the quantum well is selected as 3 in the preliminary experiment; then grow the yellow light Al y2 Ga 1-y2 N carrier confinement layer 3-4, the Al content y2 value of the carrier confinement layer 3-4 is selected to be 0.15, the thickness is 10nm, and the growth temperature is 945℃; then the yellow light multi-quantum well In x2 Ga 1-x2 N material active light-emitting layer 3-3, yellow light multiple quantum well In x2 Ga 1-x2 The N material active light emitting layer 3-3 is composed of a well layer In x21 Ga 1-x21 N and barrier layer In x22 Ga 1-x22 N alternately constituted, wherein the In component x21 of the quantum well layer is 0.36, the corresponding emission wavelength is 576nm, the thickness is 3nm, and the growth temperature is 710℃; the In component x22 of the barrier layer of the quantum well is 0.07, the thickness is 5nm, and the growth temperature is 805℃. The logarithm of the quantum well is selected as 3 in the preliminary experiment; then the p-type Mg-doped Al grown on the active light-emitting layer 3 z Ga 1-z The N electron limiting layer 4 has an Al content z value of 0.30, a thickness of 20 nm, and a growth temperature of 950°C. Since the p-NiO cap layer 5 has a high hole concentration, the electron limiting layer 4 can be prepared into a weak p-type with a carrier concentration of 10 17 / cm 3 The MOCVD process epitaxially grows a GaN buffer layer 8, an n-type (Si-doped) GaN electron injection layer 2, an undoped multi-quantum well active light-emitting layer 3 and a p-type (Mg-doped) Al z Ga 1-z The N electron confinement layer 4 uses MO sources: the aluminum source is trimethylaluminum (TMAl), the gallium source is trimethylgallium (TMGa), the indium source is triethylindium (TEIn), the nitrogen source is ammonia (NH3), the doped silicon source is silane (SiH4), and the doped magnesium source is bis(cyclopentadienyl)magnesium (Cp2Mg); then, in the p-type Mg-doped Al z Ga 1-zThe p-NiO capping layer 5 is prepared on the N electron confinement layer 4 by magnetron sputtering. The target source used in the magnetron sputtering of the p-NiO capping layer 5 is a ceramic target with NiO and 2% Li2O by mass. Table 1 shows the Hall test results of NiO thin film samples sputtered at different temperatures. In our preliminary test, the temperature was 150°C and the thickness of the p-NiO capping layer 5 was 200nm. Then, the p-NiO capping layer 5 and Al2O3 in some areas were removed by photolithography using conventional plasma etching technology. z Ga 1-z N electron confinement layer 4 and active light-emitting layer 3, GaN electron injection layer 2 is exposed in this part of the area; then Ti / Al / Ni / Au is evaporated on the part of the area where GaN electron injection layer 2 is exposed by photoresist masking and stripping technology (Lift of), and the lower electrode 7 is prepared, and the corresponding thickness is 20nm / 120nm / 50nm / 100nm; then, Au is evaporated on the part of the p-NiO cover layer 5 by photoresist masking and stripping technology, and the upper electrode 6 is prepared, and its thickness is 300nm; then the alloy is annealed under the protection of inert gas, the annealing temperature is 450℃, the time is 3 minutes, and finally it is sliced ​​into tube core. Figure 3 The voltage-current characteristic curve of the single-chip white light LED developed for us. Figure 4 This is the electrical injection spectrum of the single-chip white light LED developed for us.

[0026] Embodiment 2:

[0027] GaN single chip white light emitting tube with p-NiO as cap layer (light confinement layer and hole injection layer) and electron confinement layer (see attached) Figure 2 The preparation process is as follows: Al2O3 crystal sheet is used as substrate 1. Due to the large lattice mismatch between Al2O3 crystal and high-temperature grown GaN crystal, a 20nm thick undoped GaN buffer layer 8 is first grown at low temperature (550℃) by MOCVD, and then a 2-micron thick n-type (Si-doped, carrier concentration 4×10 18 / cm 3 )GaN electron injection layer 2 and undoped multi-quantum well active light-emitting layer 3; the growth steps of the multi-quantum well active light-emitting layer 3 are: firstly, grow blue light Al y1 Ga 1-y1 N carrier confinement layer 3-2, the Al content y1 value of the carrier confinement layer 3-2 is selected to be 0.05, the thickness is 10nm, the growth temperature is 1010℃, and the blue light multi-quantum well In is grown again. x1 Ga 1-x1 N material active light-emitting layer 3-1, blue light multi-quantum well In x1 Ga 1-x1 The N material active light emitting layer 3-1 is composed of a well layer In x11Ga 1-x11 N and barrier layer In x12 Ga 1-x12 N alternately, where the In component x11 of the quantum well layer is 0.21, the corresponding emission wavelength is 450nm, the thickness is 3nm, the growth temperature is 780℃, the In component x12 of the quantum well barrier layer is 0.07, the thickness is 5nm, the growth temperature is 855℃, and the logarithm of the quantum well is selected as 3 in the preliminary experiment; then grow the yellow light Al y2 Ga 1-y2 N carrier confinement layer 3-4, the Al content y2 value of the carrier confinement layer 3-4 is selected to be 0.15, the thickness is 10nm, the growth temperature is 950℃, and the yellow light multi-quantum well In is grown again. x2 Ga 1-x2 N material active light-emitting layer 3-3, yellow light multiple quantum well In x2 Ga 1-x2 The N material active light emitting layer 3-3 is composed of a well layer In x21 Ga 1-x21 N and barrier layer In x22 Ga 1-x22 N alternately constitutes, wherein the In component x21 of the quantum well layer is 0.36, the corresponding emission wavelength is 576nm, the thickness is 3nm, the growth temperature is 710℃, the In component x22 of the quantum well barrier layer is 0.07, the thickness is 5nm, the growth temperature is 805℃, and the number of quantum wells selected in the preliminary experiment is 3; the MO sources used in the above MOCVD process are: the aluminum source is trimethylaluminum (TMAl), the gallium source is trimethylgallium (TMGa), the indium source is triethylindium (TEIn), the nitrogen source is ammonia (NH3), and the doped silicon source is silane (SiH4); after the wafer is prepared, a p-NiO cap layer 5 is prepared on the active light-emitting layer 3 by magnetron sputtering; the target source used for the magnetron sputtering of the p-NiO cap layer 5 is NiO with a mass fraction of 2% Li2O ceramic target, Table 1 is the Hall test results of NiO thin film samples sputtered at different temperatures. In our preliminary test, the temperature was selected as 150°C and the thickness of the p-NiO cap layer 5 was 200nm; then, the p-NiO cap layer 5 and the active light-emitting layer 3 in a partial area were removed by photolithography using conventional plasma etching technology, and the GaN electron injection layer 2 was exposed in this partial area; Ti / Al / Ni / Au was evaporated in the partial area where the GaN electron injection layer 2 was exposed using the photoresist masking and stripping technology (Lift of) to prepare the lower electrode 7, and the corresponding thickness was 20nm / 120nm / 50nm / 100nm; then, Au was evaporated in the partial area of ​​the p-NiO cap layer 5 using the photoresist masking and stripping technology to prepare the upper electrode 6, and its thickness was about 300nm; then the alloy was annealed under the protection of inert gas, the annealing temperature was 450°C, the time was 3 minutes, and finally the die was diced. Figure 5This is the electrical injection spectrum at different current densities for the single-chip white light LED developed for us.

Claims

1. A GaN single-chip white light emitting tube with p-NiO as a cap layer, which comprises, from bottom to top, a substrate (1), a GaN buffer layer (8) prepared on the substrate (1), an n-type Si-doped GaN electron injection layer (2) prepared on the GaN buffer layer (8), a mutually separate multi-quantum well active light emitting layer (3) and a lower electrode (7) prepared on the GaN electron injection layer (2), a p-type Mg-doped Al2O3 layer (4) prepared on the active light emitting layer (3), and a bottom electrode (7). z Ga 1-z N electron confinement layer (4), Al z Ga 1-z The invention is composed of a cap layer (5) prepared on an N electron limiting layer (4) and an upper electrode (6) prepared on the cap layer (5), and is characterized in that: The substrate (1) is an Al2O3 or Si crystal sheet; the cap layer (5) is p-NiO with a hole concentration of 1.0×10 18 / cm 3 ~9.9×10 20 / cm 3 The multi-quantum well active light-emitting layer (3) is composed of blue light Al y1 Ga 1-y1 N carrier confinement layer (3-2), blue light multiple quantum well In x1 Ga 1-x1 N material active light emitting layer (3-1), yellow light Al y2 Ga 1-y2 N carrier confinement layer (3-4), yellow light multi-quantum well In x2 Ga 1-x2 N material active light-emitting layer (3-3) consists of four parts; blue light multiple quantum well In x1 Ga 1-x1 The N material active light emitting layer (3-1) is composed of a well layer In x11 Ga 1-x11 N and barrier layer In x12 Ga 1-x12 N alternately constituted, the number of pairs is 2 to 5; yellow light multiple quantum well In x2 Ga 1-x2 The N material active light emitting layer (3-3) is composed of a well layer In x21 Ga 1-x21 N and barrier layer In x22 Ga 1-x22 N is composed alternately, and the number of pairs is 2 to 5.

2. A GaN single-chip white light emitting tube with p-NiO as a cap layer, which is composed of, from bottom to top, a substrate (1), a GaN buffer layer (8) prepared on the substrate (1), an n-type Si-doped GaN electron injection layer (2) prepared on the GaN buffer layer (8), mutually independent multi-quantum well active light-emitting layers (3) and lower electrodes (7) prepared on the GaN electron injection layer (2), a cap layer (5) prepared on the active light-emitting layer (3), and an upper electrode (6) prepared on the cap layer (5), characterized in that: The substrate (1) is an Al2O3 or Si crystal sheet; the cap layer (5) also serves as an electron confinement layer and is p-NiO with a hole concentration of 1.0×10 18 / cm 3 ~9.9×10 20 / cm 3 The multi-quantum well active light-emitting layer (3) is composed of blue light Al y1 Ga 1-y1 N carrier confinement layer (3-2), blue light multiple quantum well In x1 Ga 1-x1 N material active light emitting layer (3-1), yellow light Al y2 Ga 1-y2 N carrier confinement layer (3-4), yellow light multi-quantum well In x2 Ga 1-x2 N material active light-emitting layer (3-3) consists of four parts; blue light multiple quantum well In x1 Ga 1-x1 The N material active light emitting layer (3-1) is composed of a well layer In x11 Ga 1-x11 N and barrier layer In x12 Ga 1-x12 N alternately constituted, the number of pairs is 2 to 5; yellow light multiple quantum well In x2 Ga 1-x2 The N material active light emitting layer (3-3) is composed of a well layer In x21 Ga 1-x21 N and barrier layer In x22 Ga 1-x22 N is composed alternately, and the number of pairs is 2 to 5.

3. A GaN single-chip white light emitting tube with p-NiO as a cap layer as claimed in claim 1 or 2, characterized in that: The selection range of the well layer x11 of the blue light quantum well is 0.15-0.22, and the selection range of the barrier layer x12 of the blue light quantum well is 0.1-0.22 smaller than x11; the selection range of the well layer x21 of the yellow light quantum well is 0.30-0.36, and the selection range of the barrier layer x22 of the yellow light quantum well is 0.1-0.30 smaller than x21; the selection range of y1 and y2 is 0-0.2, and the selection range of z is 0.1-0.

4.

4. The method for preparing a GaN single-chip white light emitting tube with p-NiO as a cap layer as claimed in claim 1, characterized in that: GaN buffer layer (8), GaN electron injection layer (2), active light emitting layer (3) and Al z Ga 1-z The N electron confinement layer (4) is prepared by MOCVD, the p-NiO cap layer (5) is prepared by magnetron sputtering, and the upper electrode (6) and the lower electrode (7) are prepared by thermal evaporation, electron beam evaporation or magnetron lasing.

5. The method for preparing a GaN single-chip white light emitting tube with p-NiO as a cap layer as claimed in claim 2, characterized in that: The GaN buffer layer (8), the GaN electron injection layer (2) and the active light-emitting layer (3) are prepared by the MOCVD method, the p-NiO cap layer (5) is prepared by the magnetron sputtering method, and the upper electrode (6) and the lower electrode (7) are prepared by thermal evaporation, electron beam evaporation or magnetron lasing.

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