Gallium nitride-based red light emitting diode and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor photoelectrons, and provides a gallium nitride-based red light emitting diode and a preparation method thereof. The epitaxial structure of the gallium nitride-based red light emitting diode sequentially comprises a sapphire substrate, a low-temperature GaN nucleating layer, a high-temperature non-doped GaN buffer layer, an n-type GaN layer, a composite stress release layer, an In < x > Ga < 1-x > N / In < y > Ga < 1-y > N multi-quantum well light emitting layer, a low-temperature p-type protective layer, a p-Aly < 1 > Ga < 1-y > N electron barrier layer, a high-temperature p-type GaN layer and a p-type InGaN contact layer from bottom to top. The V-shaped layer and the Inx1Ga1-x1N / GaN superlattice structure layer are introduced between the n-type GaN layer and the In < x > Ga < 1-x > N / In < y > Ga < 1-y > N multi-quantum well light-emitting layer to perform stress release, so that the influence of a piezoelectric polarization field on the spatial distribution of an electron hole wave function is reduced, and the radiation recombination light-emitting efficiency of an active region is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic technologies, and in particular, to a gallium nitride-based red light-emitting diode and a method for preparing the same. Background Art

[0002] In the field of LED full-color displays, red, green, and blue primary color light sources are required. Currently, red LEDs are usually based on the second-generation semiconductor AlInGaP material system. Blue and green LEDs are based on the third-generation semiconductor AlInGaN material system. A number of studies have shown that for red LEDs based on phosphide structures, performance such as external quantum efficiency will decrease as the chip size shrinks. When the chip size shrinks to the micron scale, due to the long carrier diffusion length and high-density surface defects on the sidewalls, the performance loss will be more serious, and the efficiency will drop sharply to less than 1%. In addition, in the mass transfer process of Micro LED chips, the disadvantages of the second-generation semiconductor AlGaInP material system are also obvious. Mass transfer requires the material to have good mechanical strength to avoid cracking during chip picking and placement, while the poor mechanical properties of the AlGaInP material will add new problems to mass transfer. From an environmental protection perspective, the P source used in the growth of AlGaInP is highly toxic, so it is not suitable for the sustainable development strategy. Compared with the existing red light based on AlInGaP, the InGaN-based red LED has better mechanical stability and a shorter hole diffusion length. For GaN-based LEDs, due to sidewall passivation or chemical treatment, the peak EQE can be maintained, and it is compatible with InGaN-based green and blue Micro LEDs. At the same time, the InGaN-based red Micro LED has a lower manufacturing cost, can be extended to larger 200 mm or 300 mm wafers, and has better thermal / cold coefficients, so it is extremely attractive. However, when the emission wavelength of InGaN-based LEDs is extended to long wavelengths, its efficiency decays severely, which is still a challenge for InGaN-based red LEDs. To achieve red light emission, the indium composition in the InGaN / GaN multiple quantum wells (MQWs) should be higher than 40%. Growing high-In-component InGaN quantum wells usually requires a lower growth temperature. In this case, NH 3It is difficult to cleave, the atomic mobility decreases, resulting in insufficient active N source and increased point defects. At the same time, as the In component increases, the lattice mismatch and thermal mismatch between the InGaN / GaN quantum well barriers are larger, generating a strong polarization electric field in the InGaN quantum well (QW) region, leading to a strong quantum-confined Stark effect. For orange-red LEDs with a high In component, the polarization electric field in the InGaN quantum well region is as high as 3 - 6 MV / cm. The huge polarization electric field will cause band tilting in the orange-red InGaN quantum well region, resulting in a reduction in the overlap of the wave functions of electrons and holes, a decrease in the radiative recombination rate, and a decline in the internal quantum efficiency. The polarization electric field will also cause band bending in the InGaN / GaN quantum well barriers, hindering the injection of electrons and holes, resulting in uneven distribution of electrons and holes in different quantum well regions, and further reducing the internal quantum efficiency (IQE). Although various methods have been adopted to improve the quantum efficiency of InGaN-based red LEDs, the reported quantum efficiency of InGaN-based red LEDs is still very low and cannot meet the application requirements. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems in the prior art and provide a gallium nitride-based red light-emitting diode and a preparation method thereof.

[0004] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a gallium nitride-based red light-emitting diode, and the epitaxial structure of the gallium nitride-based red light-emitting diode from bottom to top is successively:

[0006] Sapphire substrate, low-temperature GaN nucleation layer, high-temperature undoped GaN buffer layer, n-type GaN layer, composite stress release layer, In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer, low-temperature p-type protective layer, p-Al y1 Ga 1-y1 N electron blocking layer, high-temperature p-type GaN layer, p-type InGaN contact layer.

[0007] Preferably, the structure of the composite stress release layer from bottom to top is successively: V-shaped layer, In x1 Ga 1-x1 N / GaN superlattice structure layer.

[0008] Preferably, the thickness of the V-shaped layer is 10 - 300 nm;

[0009] The structure of the V-shaped layer from bottom to top is successively: high-temperature GaN barrier layer 1, low-temperature InGaN / GaN multiple quantum well, high-temperature GaN barrier layer 2;

[0010] The number of periods of the low-temperature InGaN / GaN multiple quantum wells is 2 to 10.

[0011] Preferably, the x1 Ga 1-x1 number of periods of the InGaN / GaN superlattice structure layer is 1 to 50;

[0012] In x1 Ga 1-x1 The In composition in the InGaN / GaN superlattice structure layer increases or decreases along the growth direction;

[0013] In x1 Ga 1-x1 The value of x1 in the InGaN / GaN superlattice structure layer is 1% to 35%;

[0014] In x1 Ga 1-x1 In the InGaN / GaN superlattice structure layer, the thickness of the InGaN layer x1 Ga 1-x1 shows a gradient change;

[0015] In x1 Ga 1-x1 The thinnest InGaN layer in the InGaN / GaN superlattice structure layer x1 Ga 1-x1 has a thickness of 0.5 to 1.5 nm, and the thickest InGaN layer x1 Ga 1-x1 has a thickness of 4.5 to 5.5 nm;

[0016] In x1 Ga 1-x1 In the InGaN / GaN superlattice structure layer, the thickness of the GaN layer

[0017] In x1 Ga 1-x1 shows a gradient change; the thinnest GaN layer has a thickness of 0.5 to 1.5 nm, and the thickest GaN layer has a thickness of 4.5 to 5.5 nm.

[0018] Preferably, the thickness of the low-temperature GaN nucleation layer is 10 to 100 nm, the thickness of the high-temperature undoped GaN buffer layer is 1 to 10 μm, and the thickness of the n-type GaN layer is 2 to 6 μm.

[0019] Preferably, the x Ga 1-x number of periods of the InGaN / InGaN multiple quantum well light-emitting layer is 1 to 10; y Ga 1-y

[0020] In xGa 1-x N / In y Ga 1-y In in the GaN multiple quantum well light-emitting layer x Ga 1-x The value of x in the GaN layer ranges from 0.35 to 0.5; In x Ga 1-x The thickness of the GaN layer is 1 - 3 nm;

[0021] In x Ga 1-x N / In y Ga 1-y In in the GaN multiple quantum well light-emitting layer y Ga 1-y The value of y in the GaN layer ranges from 0 to 0.1; In y Ga 1-y The thickness of the GaN layer is 2 - 30 nm;

[0022] The thickness of the low-temperature p-type protective layer is 10 - 100 nm.

[0023] Preferably, the value of y1 in the p-Al y1 Ga 1-y1 N electron blocking layer ranges from 0.01 to 0.3, and the thickness of the p-Al y1 Ga 1-y1 N electron blocking layer is 1 - 50 nm;

[0024] The thickness of the high-temperature p-type GaN layer is 10 - 200 nm;

[0025] The thickness of the p-type InGaN contact layer is 1 - 5 nm.

[0026] The present invention also provides a method for manufacturing the gallium nitride-based red light-emitting diode, comprising the following steps:

[0027] (1) In a hydrogen atmosphere, the sapphire substrate is pretreated and then a low-temperature GaN nucleation layer is grown;

[0028] (2) In a hydrogen atmosphere, a high-temperature undoped GaN buffer layer and an n-type GaN layer are sequentially grown;

[0029] (3) In a protective atmosphere, a composite stress release layer and In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer are sequentially grown;

[0030] (4) In In x Ga 1-x N / In y Ga 1-yA low-temperature p-type protective layer and a p-Al y1 Ga 1-y1 N electron blocking layer are sequentially grown on the surface of the multi-quantum well light-emitting layer;

[0031] (5) In a hydrogen atmosphere, a high-temperature p-type GaN layer is grown; then in a protective atmosphere, a p-type InGaN contact layer is grown to obtain the gallium nitride-based red light-emitting diode.

[0032] Preferably, in step (1), the temperature of the pretreatment is 1080-1100 °C, the pressure is 80-120 torr, and the time is 5-10 min;

[0033] In step (1), the growth temperature of the low-temperature GaN nucleation layer is 450-600 °C, and the growth pressure is 300-1000 torr;

[0034] In step (2), the growth temperature of the high-temperature undoped GaN buffer layer is 1000-1500 °C, and the growth pressure is 100-500 torr;

[0035] In step (2), the growth temperature of the n-type GaN layer is 1000-1500 °C, and the growth pressure is 100-500 torr;

[0036] During the growth of the composite stress release layer in step (3), a V-shaped layer is first grown and then an In x1 Ga 1-x1 N / GaN superlattice structure layer;

[0037] The growth temperature of the V-shaped layer is 700-950 °C, and the growth pressure is 100-1000 torr;

[0038] In x1 Ga 1-x1 The growth temperature of the N / GaN superlattice structure layer is 700-950 °C, and the growth pressure is 100-1000 torr;

[0039] In step (3), the In x Ga 1-x N / In y Ga 1-y The growth temperature of the multi-quantum well light-emitting layer is 650-900 °C, and the growth pressure is 100-1000 torr.

[0040] Preferably, in step (4), the growth temperature of the low-temperature p-type protective layer is 700-900 °C, and the growth pressure is 100-1000 torr;

[0041] In step (4), p-Al y1 Ga 1-y1The growth temperature of the N electron blocking layer is 800 - 1000 °C;

[0042] In step (5), the growth temperature of the high-temperature p-type GaN layer is 850 - 1050 °C, and the growth pressure is 100 - 500 torr;

[0043] In step (5), the growth temperature of the p-type InGaN contact layer is 650 - 750 °C, and the growth pressure is 200 - 400 torr.

[0044] The present invention provides a gallium nitride-based red light-emitting diode. The epitaxial structure of the gallium nitride-based red light-emitting diode from bottom to top is successively: sapphire substrate, low-temperature GaN nucleation layer, high-temperature undoped GaN buffer layer, n-type GaN layer, composite stress release layer, In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer, low-temperature p-type protective layer, p-Al y1 Ga 1-y1 N electron blocking layer, high-temperature p-type GaN layer, p-type InGaN contact layer. In the present invention, a V-shaped layer and an In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer are introduced between the n-type GaN layer and the In x1 Ga 1-x1 N / GaN superlattice structure layer for stress release, forming a specific density of V-shaped layer distribution below the active region. The V-shaped layer can effectively shield the influence of penetrating dislocations on the light-emitting device and improve the radiative recombination light-emitting efficiency. The stress release layer with a gradually changing In composition gradually and orderly releases the compressive stress accumulated during the growth of the epitaxial material along the growth direction, improves the absorption efficiency of In in the red light active region, reduces the influence of the piezoelectric polarization field on the spatial distribution of the electron-hole wave function, and improves the radiative recombination light-emitting efficiency of the active region. Description of the Drawings

[0045] Figure 1 Schematic structural diagram of the gallium nitride-based red light-emitting diode prepared in Example 1;

[0046] Figure 2 Schematic structural diagram of the gallium nitride-based red light-emitting diode prepared in Comparative Example 1;

[0047] Figure 3 Schematic structural diagram of the gallium nitride-based red light-emitting diode prepared in Comparative Example 2;

[0048] Figure 4 Internal quantum efficiency test chart of the gallium nitride-based red light-emitting diodes in Example 1, Comparative Example 1 and Comparative Example 2. Detailed implementation mode

[0049] The present invention provides a gallium nitride-based red light-emitting diode, and the epitaxial structure of the gallium nitride-based red light-emitting diode from bottom to top is as follows:

[0050] Sapphire substrate, low-temperature GaN nucleation layer, high-temperature undoped GaN buffer layer, n-type GaN layer, composite stress release layer, In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer, low-temperature p-type protective layer, p-Al y1 Ga 1-y1 N electron blocking layer, high-temperature p-type GaN layer, p-type InGaN contact layer.

[0051] In the present invention, the structure of the composite stress release layer from bottom to top is as follows: V-shaped layer, In x1 Ga 1-x1 N / GaN superlattice structure layer.

[0052] In the present invention, the thickness of the V-shaped layer is preferably 10-300 nm, more preferably 50-250 nm, and even more preferably 100-200 nm.

[0053] In the present invention, the structure of the V-shaped layer from bottom to top is as follows: high-temperature GaN barrier layer 1, low-temperature InGaN / GaN multiple quantum well, high-temperature GaN barrier layer 2.

[0054] In the present invention, the number of periods of the low-temperature InGaN / GaN multiple quantum well is preferably 2-10, and more preferably 3, 4, 5, 6, 7, 8, 9.

[0055] In the present invention, In x1 Ga 1-x1 The number of periods of the N / GaN superlattice structure layer is preferably 1-50, more preferably 10-40, and even more preferably 20-30.

[0056] In the present invention, In x1 Ga 1-x1 The In composition in the N / GaN superlattice structure layer increases or decreases along the growth direction.

[0057] In the present invention, In x1 Ga 1-x1 The value of x1 in the N / GaN superlattice structure layer is preferably 1%-35%, more preferably 5%-30%, and even more preferably 10%-20%.

[0058] In the present invention, In x1 Ga1-x1 In in the InGaN superlattice structure layer x1 Ga 1-x1 The thickness of the InGaN layer shows a gradient change, increasing or decreasing in thickness with the increase of the In component, and increasing or decreasing in thickness with the decrease of the In component.

[0059] In the present invention, In x1 Ga 1-x1 The thickness of the thinnest InGaN layer in the InGaN superlattice structure layer x1 Ga 1-x1 The thickness of the thinnest InGaN layer is preferably 0.5 - 1.5 nm, more preferably 0.6 - 1.4 nm, and even more preferably 0.8 - 1.2 nm; the thickness of the thickest InGaN layer x1 Ga 1-x1 The thickness of the thickest InGaN layer is preferably 4.5 - 5.5 nm, more preferably 4.6 - 5.4 nm, and even more preferably 4.8 - 5.2 nm.

[0060] In the present invention, In x1 Ga 1-x1 The thickness of the GaN layer in the InGaN superlattice structure layer shows a gradient change, increasing or decreasing in thickness with the increase of the In component, and increasing or decreasing in thickness with the decrease of the In component.

[0061] In the present invention, In x1 Ga 1-x1 The thickness of the thinnest GaN layer in the InGaN superlattice structure layer is preferably 0.5 - 1.5 nm, more preferably 0.6 - 1.4 nm, and even more preferably 0.8 - 1.2 nm; the thickness of the thickest GaN layer is preferably 4.5 - 5.5 nm, more preferably 4.6 - 5.4 nm, and even more preferably 4.8 - 5.2 nm.

[0062] In the present invention, the thickness of the low-temperature GaN nucleation layer is preferably 10 - 100 nm, more preferably 20 - 80 nm, and even more preferably 40 - 60 nm; the thickness of the high-temperature undoped GaN buffer layer is preferably 1 - 10 μm, more preferably 2 - 8 μm, and even more preferably 4 - 6 μm; the thickness of the n-type GaN layer is preferably 2 - 6 μm, more preferably 3 - 5 μm, and even more preferably 3.5 - 4 μm.

[0063] In the present invention, the In x Ga 1-x N / In y Ga 1-y The period of the InGaN multiple quantum well light-emitting layer is preferably 1 - 10, more preferably 2 - 8, and even more preferably 4 - 6.

[0064] In the present invention, In xGa 1-x N / In y Ga 1-y In in the GaN multiple quantum well light-emitting layer x Ga 1-x In the GaN layer, the value of x is preferably 0.35 - 0.5, more preferably 0.4 - 0.45, and even more preferably 0.42 - 0.43; In x Ga 1-x The thickness of the GaN layer is preferably 1 - 3 nm, more preferably 1.5 - 2.5 nm, and even more preferably 1.8 - 2.3 nm.

[0065] In the present invention, In x Ga 1-x N / In y Ga 1-y In in the GaN multiple quantum well light-emitting layer y Ga 1-y In the GaN layer, the value of y is preferably 0 - 0.1, more preferably 0.02 - 0.08, and even more preferably 0.04 - 0.06; In y Ga 1-y The thickness of the GaN layer is preferably 2 - 30 nm, more preferably 5 - 25 nm, and even more preferably 10 - 20 nm.

[0066] In the present invention, the thickness of the low-temperature p-type protective layer is preferably 10 - 100 nm, more preferably 20 - 80 nm, and even more preferably 40 - 60 nm.

[0067] In the present invention, in the p-Al y1 Ga 1-y1 In the N electron blocking layer, the value of y1 is preferably 0.01 - 0.3, more preferably 0.05 - 0.25, and even more preferably 0.1 - 0.2; in the p-Al y1 Ga 1-y1 The thickness of the N electron blocking layer is preferably 1 - 50 nm, more preferably 10 - 40 nm, and even more preferably 20 - 30 nm.

[0068] In the present invention, the thickness of the high-temperature p-type GaN layer is preferably 10 - 200 nm, more preferably 50 - 150 nm, and even more preferably 80 - 120 nm.

[0069] In the present invention, the thickness of the p-type InGaN contact layer is preferably 1 - 5 nm, more preferably 1.5 - 4.5 nm, and even more preferably 2 - 3 nm.

[0070] The present invention also provides a method for preparing the gallium nitride-based red light-emitting diode, comprising the following steps:

[0071] (1) After pre-treating the sapphire substrate in a hydrogen atmosphere, a low-temperature GaN nucleation layer is grown;

[0072] (2) In a hydrogen atmosphere, a high-temperature undoped GaN buffer layer and an n-type GaN layer are sequentially grown;

[0073] (3) In a protective atmosphere, a composite stress release layer, In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layers are sequentially grown;

[0074] (4) On the surface of the In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layers, a low-temperature p-type protective layer and a p-Al y1 Ga 1-y1 N electron blocking layer are sequentially grown;

[0075] (5) In a hydrogen atmosphere, a high-temperature p-type GaN layer is grown; then in a protective atmosphere, a p-type InGaN contact layer is grown to obtain the gallium nitride-based red light-emitting diode.

[0076] In the present invention, in step (1), the temperature of the pre-treatment is preferably 1080 - 1100 °C, more preferably 1085 - 1095 °C, and even more preferably 1088 - 1092 °C; the pressure is preferably 80 - 120 torr, more preferably 85 - 115 torr, and even more preferably 90 - 110 torr; the time is preferably 5 - 10 min, more preferably 6 - 9 min, and even more preferably 7 - 8 min.

[0077] In the present invention, in step (1), the growth temperature of the low-temperature GaN nucleation layer is preferably 450 - 600 °C, more preferably 500 - 550 °C, and even more preferably 520 - 530 °C; the growth pressure is preferably 300 - 1000 torr, more preferably 400 - 900 torr, and even more preferably 600 - 800 torr.

[0078] In the present invention, in step (2), the growth temperature of the high-temperature undoped GaN buffer layer is preferably 1000 - 1500 °C, more preferably 1100 - 1400 °C, and even more preferably 1200 - 1300 °C; the growth pressure is preferably 100 - 500 torr, more preferably 200 - 400 torr, and even more preferably 250 - 350 torr.

[0079] In the present invention, in step (2), the growth temperature of the n-type GaN layer is preferably 1000 - 1500 °C, more preferably 1100 - 1400 °C, and even more preferably 1200 - 1300 °C; the growth pressure is preferably 100 - 500 torr, more preferably 200 - 400 torr, and even more preferably 250 - 350 torr.

[0080] In the present invention, the protective atmosphere in step (3) is preferably nitrogen or argon.

[0081] In the present invention, during the growth of the composite stress release layer in step (3), the V-shaped layer is grown first and then the In x1 Ga 1-x1 N / GaN superlattice structure layer.

[0082] In the present invention, the growth temperature of the V-shaped layer is preferably 700 - 950 °C, more preferably 750 - 900 °C, and even more preferably 800 - 850 °C; the growth pressure is preferably 100 - 1000 torr, more preferably 200 - 800 torr, and even more preferably 400 - 600 torr.

[0083] In the present invention, when growing the V-shaped layer, it is grown in the order of high-temperature GaN barrier layer 1, low-temperature InGaN / GaN multiple quantum wells, and high-temperature GaN barrier layer 2.

[0084] In the present invention, the growth temperature of the high-temperature GaN barrier layer 1 is preferably 850 - 910 °C, more preferably 860 - 900 °C, and even more preferably 870 - 880 °C.

[0085] In the present invention, the growth temperature of the low-temperature InGaN / GaN multiple quantum wells is preferably 800 - 840 °C, more preferably 805 - 835 °C, and even more preferably 810 - 820 °C.

[0086] In the present invention, when growing the low-temperature InGaN / GaN multiple quantum wells, the GaN layer is grown first, and then the InGaN layer is grown on the surface of the GaN layer, thus obtaining one period of InGaN / GaN, and then the growth of the next period is carried out.

[0087] In the present invention, the growth temperature of the high-temperature GaN barrier layer 2 is preferably 850 - 910 °C, more preferably 860 - 900 °C, and even more preferably 870 - 880 °C.

[0088] In the present invention, In x1 Ga 1-x1The growth temperature of the N / GaN superlattice structure layer is preferably 700 - 950 °C, more preferably 750 - 900 °C, and even more preferably 800 - 850 °C; the growth pressure is preferably 100 - 1000 torr, more preferably 200 - 800 torr, and even more preferably 400 - 600 torr.

[0089] In the present invention, when growing the In x1 Ga 1-x1 N / GaN superlattice structure layer, first grow the GaN layer, and then grow the In x1 Ga 1-x1 N layer on the surface of the GaN layer, thus obtaining one period of In x1 Ga 1-x1 N / GaN, and then proceed with the growth of the next period.

[0090] In the present invention, in step (3), the growth temperature of the In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer is preferably 650 - 900 °C, more preferably 700 - 850 °C, and even more preferably 750 - 800 °C; the growth pressure is preferably 100 - 1000 torr, more preferably 200 - 800 torr, and even more preferably 400 - 600 torr.

[0091] In the present invention, the growth range of the low-temperature p-type protective layer and the p-Al y1 Ga 1-y1 N electron blocking layer is a nitrogen atmosphere or a nitrogen-hydrogen mixed atmosphere.

[0092] In the present invention, in step (4), the growth temperature of the low-temperature p-type protective layer is preferably 700 - 900 °C, more preferably 750 - 850 °C, and even more preferably 770 - 820 °C; the growth pressure is preferably 100 - 1000 torr, more preferably 200 - 800 torr, and even more preferably 400 - 600 torr.

[0093] In the present invention, in step (4), the growth temperature of the p-Al y1 Ga 1-y1 N electron blocking layer is preferably 800 - 1000 °C, more preferably 850 - 950 °C, and even more preferably 880 - 920 °C.

[0094] In the present invention, in step (5), the growth temperature of the high-temperature p-type GaN layer is preferably 850 - 1050 °C, more preferably 900 - 1000 °C, and still more preferably 940 - 960 °C; the growth pressure is preferably 100 - 500 torr, more preferably 200 - 400 torr, and still more preferably 250 - 350 torr.

[0095] In the present invention, the protective atmosphere in step (5) is preferably nitrogen or argon.

[0096] In the present invention, in step (5), the growth temperature of the p-type InGaN contact layer is preferably 650 - 750 °C, more preferably 660 - 740 °C, and still more preferably 680 - 720 °C; the growth pressure is preferably 200 - 400 torr, more preferably 250 - 350 torr, and still more preferably 280 - 320 torr.

[0097] In the present invention, after the growth of the p-type InGaN contact layer is completed, the temperature is decreased. The target temperature for temperature decrease is preferably 700 - 800 °C, more preferably 720 - 780 °C, and still more preferably 740 - 760 °C; then annealing is performed in a nitrogen atmosphere. The annealing time is preferably 5 - 20 min, more preferably 10 - 15 min, and still more preferably 12 - 13 min; after the annealing is completed, secondary temperature decrease is performed. The target temperature for secondary temperature decrease is preferably 20 - 30 °C, more preferably 22 - 28 °C, and still more preferably 24 - 26 °C; the growth is ended.

[0098] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0099] Example 1

[0100] Using the close-coupled vertical reactor MOCVD growth system of Aixtron company, trimethylgallium (TMGa), trimethylindium (TMIn), and trimethylaluminum (TMAl) are used as group III sources during the growth process, ammonia (NH 3 ) is used as the group V source, and silane (SiH4) is used as the n-type doping source, and bis(cyclopentadienyl)magnesium (Cp 2 Mg) is used as the p-type doping source.

[0101] The sapphire substrate is treated in a hydrogen atmosphere at 1080 °C with a reaction chamber pressure of 100 torr for 10 minutes, and then the temperature is lowered. At 530 °C with a reaction chamber pressure of 500 torr in a hydrogen atmosphere, a 25-nm-thick low-temperature GaN nucleation layer is grown; at 1050 °C with a reaction chamber pressure of 300 torr in a hydrogen atmosphere, a 2-μm-thick high-temperature undoped GaN buffer layer is grown; at 1050 °C with a reaction chamber pressure of 100 torr in a hydrogen atmosphere, a 3-μm-thick n-type GaN layer is grown; the Si doping concentration is 5×10 18 cm -3 ; in a nitrogen atmosphere with a reaction chamber pressure of 500 torr, a 300-nm-thick V-shaped layer is grown. The V-shaped layer is composed of a composite structure of a high-temperature GaN barrier layer 1, a low-temperature InGaN / GaN multiple quantum well, and a high-temperature GaN barrier layer 2. The number of periods of the InGaN / GaN quantum well is 5. The growth temperature of the high-temperature GaN barrier layer 1 is 850 °C, the growth temperature of the low-temperature InGaN / GaN multiple quantum well is 800 °C. When growing the low-temperature InGaN / GaN multiple quantum well, a GaN layer is grown first, and then an InGaN layer is grown on the surface of the GaN layer, so as to obtain one period of InGaN / GaN, and then the growth of the next period is carried out. The growth temperature of the high-temperature GaN barrier layer 2 is 850 °C. Then, an In x1 Ga 1-x1 N / GaN superlattice structure layer is grown, where the number of periods of the superlattice structure is 25, the In composition increases step by step along the growth direction, the bottom layer is In 0.01 Ga 0.99 N / GaN, and the top layer is In 0.25 Ga 0.75 N / GaN. The thickness of the thinnest layer of In x1 Ga 1-x1 N is 1 nm, the thickness of the thickest layer of In x1 Ga 1-x1 N is 5 nm, the thickness of the thinnest layer of GaN is 1 nm, the thickness of the thickest layer of GaN is 5 nm, and the Si doping concentration of the barrier layer is 2×10 18 cm -3 ; at 700 °C in a nitrogen atmosphere with a V / III molar ratio of 20000 and a reaction chamber pressure of 300 torr, 3 periods of In 0.4 Ga 0.6 N / GaN multiple quantum well active regions are grown, where the thickness of the In 0.4 Ga 0.6 N quantum well layer is 2.5 nm; the thickness of the GaN barrier layer is 10 nm; at 800 °C on the active region in a nitrogen-hydrogen mixed atmosphere with a reaction chamber pressure of 300 torr, a 50-nm-thick low-temperature p-type protective layer is grown; at 940 °C, p-Al 0.15 Ga0.85 N electron blocking layer, where the thickness of the electron blocking layer is 20 nm. The Mg doping concentration is 5×10 17 cm -3 . At 940 °C, in a hydrogen atmosphere, the reaction chamber pressure is 100 torr, and a 100-nm high-temperature p-type GaN layer is grown. The Mg doping concentration is 5×10 17 cm -3 ; at 700 °C, in a nitrogen atmosphere, the reaction chamber pressure is 300 torr, and a 3-nm p-type InGaN contact layer is grown. The Mg doping concentration is 2×10 18 cm -3 .

[0102] The schematic structural diagram of the gallium nitride-based red light-emitting diode prepared in this embodiment is as shown in Figure 1 . Figure 1 . From bottom to top in sequence are: sapphire substrate 301, low-temperature GaN nucleation layer 302, high-temperature undoped GaN buffer layer 303, n-type GaN layer 304, V-shaped layer 305, In x1 Ga 1-x1 N / GaN superlattice structure layer 306, In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer 307, low-temperature p-type protective layer 308, p-Al y1 Ga 1-y1 N electron blocking layer 309, high-temperature p-type GaN layer 310, p-type InGaN contact layer 311.

[0103] Comparative Example 1

[0104] Use the Aixtron company, close-coupled vertical reactor MOCVD growth system. During the growth process, trimethylgallium (TMGa), trimethylindium (TMIn), and trimethylaluminum (TMAl) are used as group III sources, ammonia gas (NH 3 ) as the group V source, silane (SiH 4 ) as the n-type doping source, and bis(cyclopentadienyl)magnesium (Cp 2Using Mg as a p-type doping source, first, in a metalorganic chemical vapor deposition reaction chamber, a sapphire substrate is treated in a hydrogen atmosphere at 1080 °C with a reaction chamber pressure of 100 torr for 10 minutes. Then, the temperature is lowered, and at 530 °C with a reaction chamber pressure of 500 torr, a 25-nm-thick low-temperature GaN nucleation layer is grown three-dimensionally in a hydrogen atmosphere; at 1050 °C with a reaction chamber pressure of 300 torr, a 2-μm-thick high-temperature undoped GaN buffer layer is grown in a hydrogen atmosphere; at 1050 °C with a reaction chamber pressure of 100 torr, a 3-μm-thick n-type GaN layer is grown in a hydrogen atmosphere; the Si doping concentration is 5×10 18 cm -3 ; at 700 °C - 950 °C with a reaction chamber pressure of 100 - 1000 torr, a 300-nm-thick V-shaped layer is grown. The V-shaped layer has a composite structure composed of a high-temperature GaN barrier layer 1, a low-temperature InGaN / GaN multiple quantum well, and a high-temperature GaN barrier layer 2. The number of periods of the InGaN / GaN quantum well is 4. The growth temperature of the high-temperature GaN barrier layer 1 is 850 °C, the growth temperature of the low-temperature InGaN / GaN multiple quantum well is 800 °C, and the growth temperature of the high-temperature GaN barrier layer 2 is 850 °C. At 700 °C in a nitrogen atmosphere with a reaction chamber pressure of 300 torr, 3 periods of In 0.4 Ga 0.6 N / GaN multiple quantum well active regions are then grown, where the thickness of the In 0.4 Ga 0.6 N quantum well layer is 2.5 nm; the thickness of the GaN barrier layer is 10 nm; at 800 °C on the active region, in a nitrogen atmosphere or a nitrogen-hydrogen mixed atmosphere with a reaction chamber pressure of 300 torr, a 50-nm-thick low-temperature p-type protective layer is grown; at 940 °C, a p-Al 0.15 Ga 0.85 N electron blocking layer is grown, where the thickness of the electron blocking layer is 20 nm. The Mg doping concentration is 5×10 17 cm -3 . At 940 °C in a hydrogen atmosphere with a reaction chamber pressure of 100 torr, a 100-nm-thick high-temperature p-type GaN layer is grown. The Mg doping concentration is 5×10 17 cm -3 ; at 700 °C in a nitrogen atmosphere with a reaction chamber pressure of 300 torr, a 3-nm-thick p-type InGaN contact layer is grown. The Mg doping concentration is 2×10 18 cm -3 .

[0105] Figure 2 Figure 32 shows the structural schematic diagram of the gallium nitride-based red light-emitting diode prepared in Comparative Example 1. Figure 2From bottom to top, they are: sapphire substrate 101, low-temperature GaN nucleation layer 102, high-temperature undoped GaN buffer layer 103, n-type GaN layer 104, V-shaped layer 105, In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer 106, low-temperature p-type protective layer 107, p-Al y1 Ga 1-y1 N electron blocking layer 108, high-temperature p-type GaN layer 109, p-type InGaN contact layer 110.

[0106] Comparative Example 2

[0107] Use the Aixtron company's close-coupled vertical reactor MOCVD growth system. During the growth process, trimethylgallium (TMGa), trimethylindium (TMIn), and trimethylaluminum (TMAl) are used as group III sources, ammonia gas (NH 3 ) as the group V source, silane (SiH 4 ) as the n-type doping source, and bis(cyclopentadienyl)magnesium (Cp 2 Mg) as the p-type doping source. First, in the metalorganic chemical vapor deposition reactor, the sapphire substrate is reacted in a hydrogen atmosphere at 1080 °C with a reactor pressure of 100 torr for 10 minutes, then the temperature is lowered, and at 530 °C with a reactor pressure of 500 torr, a 25-nm-thick low-temperature GaN nucleation layer is grown three-dimensionally in a hydrogen atmosphere; at 1050 °C with a reactor pressure of 300 torr, a 2-μm-thick high-temperature undoped GaN buffer layer is grown in a hydrogen atmosphere; at 1050 °C with a reactor pressure of 100 torr, a 3-μm-thick n-type GaN layer is grown in a hydrogen atmosphere; the Si doping concentration is 5×10 18 cm -3 ; at 700 °C - 950 °C in a nitrogen atmosphere with a reactor pressure of 100 - 1000 torr, an InGaN / GaN superlattice with a gradually changing In composition is grown, where the number of superlattice structure periods is 25, and the In composition increases stepwise along the growth direction. The bottom layer is In 0.01 Ga 0.99 N / GaN, and the top layer is In 0.25 Ga 0.75 N / GaN. The thickness of the thinnest layer of In x1 Ga 1-x1 N is 1 nm, the thickness of the thickest layer of In x1 Ga 1-x1 N is 5 nm, the thickness of the thinnest layer of GaN is 1 nm, the thickness of the thickest layer of GaN is 5 nm, and the Si doping concentration in the barrier layer is 2×10 18 cm -3; At 700 °C, in a nitrogen atmosphere, with a V / III molar ratio of 20,000, a reaction chamber pressure of 300 torr, followed by growing 3 cycles of In 0.4 Ga 0.6 N / GaN multiple quantum well active region, where the thickness of the In 0.4 Ga 0.6 N quantum well layer is 2.5 nm; the thickness of the GaN barrier layer is 10 nm; at 800 °C, on the active region, in a mixed nitrogen-hydrogen atmosphere, with a reaction chamber pressure of 300 torr, grow a 50-nm low-temperature p-type protective layer; at 940 °C, grow a p-Al 0.15 Ga 0.85 N electron blocking layer, where the thickness of the electron blocking layer is 20 nm. The Mg doping concentration is 5×10 17 cm -3 . At 940 °C, in a hydrogen atmosphere, with a reaction chamber pressure of 100 torr, grow a 100-nm high-temperature p-type GaN layer. The Mg doping concentration is 5×10 17 cm -3 ; At 700 °C, in a nitrogen atmosphere, with a reaction chamber pressure of 300 torr, grow a 3-nm p-type InGaN contact layer. The Mg doping concentration is 2×10 18 cm -3 .

[0108] Figure 3 is a schematic structural diagram of a gallium nitride-based red light-emitting diode prepared in Comparative Example 2, Figure 3 in which, in the order from bottom to top, are: sapphire substrate 201, low-temperature GaN nucleation layer 202, high-temperature undoped GaN buffer layer 203, n-type GaN layer 204, In x1 Ga 1-x1 N / GaN superlattice structure layer 205, In x Ga 1-x N / In y Ga 1-y N multiple quantum well light-emitting layer 206, low-temperature p-type protective layer 207, p-Al y1 Ga 1-y1 N electron blocking layer 208, high-temperature p-type GaN layer 209, p-type InGaN contact layer 210.

[0109] After the epitaxial growth in Example 1, Comparative Example 1, and Comparative Example 2 was completed, the temperature of the reaction chamber was lowered to 750 °C, and annealing treatment was carried out for 10 min in a pure nitrogen atmosphere, and then it was lowered to 25 °C to end the growth.

[0110] The internal quantum efficiency of the gallium nitride-based red light-emitting diodes prepared in Example 1, Comparative Example 1, and Comparative Example 2 was tested under variable-temperature photoluminescence, and the results are as Figure 4As shown, the variable-temperature PL test results show that the internal quantum efficiency of the sample of Example 1 with the composite stress release layer is increased by 200% and 140% compared to the samples of Comparative Example 1 and Comparative Example 2 without the composite stress release layer.

[0111] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A gallium nitride-based red light emitting diode, characterized in that: The epitaxial structure of the gallium nitride-based red light emitting diode is as follows from bottom to top: Sapphire substrate, low-temperature GaN nucleation layer, high-temperature undoped GaN buffer layer, n-type GaN layer, composite stress release layer, In x Ga 1-x N / In y Ga 1-y N multi-quantum well light-emitting layer, low-temperature p-type protective layer, p-Al y1 Ga 1-y1 N electron blocking layer, high temperature p-type GaN layer, p-type InGaN contact layer.

2. The gallium nitride-based red light emitting diode according to claim 1, characterized in that: The structure of the composite stress release layer is as follows from bottom to top: V-shaped layer, In x1 Ga 1-x1 N / GaN superlattice structure layer.

3. The gallium nitride-based red light emitting diode according to claim 2, characterized in that: The thickness of the V-shaped layer is 10 to 300 nm; The structure of the V-shaped layer is, from bottom to top, a high-temperature GaN barrier layer 1, a low-temperature InGaN / GaN multiple quantum well, and a high-temperature GaN barrier layer 2; The period number of the low-temperature InGaN / GaN multiple quantum well is 2-10.

4. The gallium nitride-based red light emitting diode according to claim 2 or 3, characterized in that: In x1 Ga 1-x1 The period number of the N / GaN superlattice structure layer is 1 to 50; In x1 Ga 1-x1 The In component in the N / GaN superlattice structure layer increases or decreases along the growth direction; In x1 Ga 1-x1 The value of x1 in the N / GaN superlattice structure layer is 1% to 35%; In x1 Ga 1-x1 In N / GaN superlattice structure layer x1 Ga 1-x1 The thickness of the N layer shows a gradient change; In x1 Ga 1-x1 The thinnest In layer in the N / GaN superlattice structure x1 Ga 1-x1 The thickness of N is 0.5 to 1.5 nm, and the thickest layer is In x1 Ga 1-x1 The thickness of N is 4.5 to 5.5 nm; In x1 Ga 1-x1 The thickness of the GaN layer in the N / GaN superlattice structure layer shows a gradient change; In x1 Ga 1-x1 The thickness of the thinnest GaN layer in the N / GaN superlattice structure layer is 0.5 to 1.5 nm, and the thickness of the thickest GaN layer is 4.5 to 5.5 nm.

5. The gallium nitride-based red light emitting diode according to claim 4, characterized in that: The thickness of the low-temperature GaN nucleation layer is 10-100 nm, the thickness of the high-temperature non-doped GaN buffer layer is 1-10 μm, and the thickness of the n-type GaN layer is 2-6 μm.

6. The gallium nitride-based red light emitting diode according to claim 5, characterized in that: In x Ga 1-x N / In y Ga 1-y The period of the N multi-quantum well light-emitting layer is 1 to 10; In x Ga 1-x N / In y Ga 1-y In N multi-quantum well light-emitting layer x Ga 1-x The value of x in the N layer is 0.35~0.5; x Ga 1-x The thickness of the N layer is 1 to 3 nm; In x Ga 1-x N / In y Ga 1-y In N multi-quantum well light-emitting layer y Ga 1-y The value of y in the N layer is 0 to 0.1; y Ga 1-y The thickness of the N layer is 2 to 30 nm; The thickness of the low-temperature p-type protection layer is 10-100 nm.

7. The gallium nitride-based red light emitting diode according to claim 6, characterized in that: The p-Al y1 Ga 1-y1 The value of y1 in the N electron blocking layer is 0.01 to 0.

3. y1 Ga 1-y1 The thickness of the N electron blocking layer is 1 to 50 nm; The thickness of the high temperature p-type GaN layer is 10 to 200 nm; The thickness of the p-type InGaN contact layer is 1-5 nm.

8. The method for preparing a gallium nitride-based red light emitting diode according to any one of claims 1 to 7, characterized in that: It includes the following steps: (1) In a hydrogen atmosphere, a sapphire substrate is pretreated to grow a low-temperature GaN nucleation layer; (2) In a hydrogen atmosphere, sequentially growing a high-temperature non-doped GaN buffer layer and an n-type GaN layer; (3) In a protective atmosphere, the composite stress release layer, In x Ga 1-x N / In y Ga 1-y N multi-quantum well light-emitting layer; (4)In x Ga 1-x N / In y Ga 1-y The surface of the N multi-quantum well light-emitting layer is sequentially grown with a low-temperature p-type protective layer, a p-Al y1 Ga 1-y1 N electron blocking layer; (5) growing a high-temperature p-type GaN layer in a hydrogen atmosphere; and then growing a p-type InGaN contact layer in a protective atmosphere to obtain the gallium nitride-based red light emitting diode.

9. The method for preparing a gallium nitride-based red light emitting diode according to claim 8, characterized in that: The pretreatment temperature in step (1) is 1080-1100° C., the pressure is 80-120 torr, and the time is 5-10 min; In step (1), the growth temperature of the low-temperature GaN nucleation layer is 450-600° C., and the growth pressure is 300-1000 torr; In step (2), the growth temperature of the high temperature non-doped GaN buffer layer is 1000-1500° C., and the growth pressure is 100-500 torr; In step (2), the growth temperature of the n-type GaN layer is 1000-1500° C., and the growth pressure is 100-500 torr; During the growth of the composite stress release layer in step (3), the V-shaped layer is first grown and then the In x1 Ga 1-x1 N / GaN superlattice structure layer; The growth temperature of the V-shaped layer is 700-950°C and the growth pressure is 100-1000 torr; In x1 Ga 1-x1 The growth temperature of the N / GaN superlattice structure layer is 700-950°C, and the growth pressure is 100-1000 torr; In step (3) x Ga 1-x N / In y Ga 1-y The growth temperature of the N multi-quantum well light-emitting layer is 650-900° C., and the growth pressure is 100-1000 torr.

10. The method for preparing a gallium nitride-based red light emitting diode according to claim 8 or 9, characterized in that: In step (4), the growth temperature of the low-temperature p-type protective layer is 700-900° C., and the growth pressure is 100-1000 torr; In step (4), p-Al y1 Ga 1-y1 The growth temperature of the N electron blocking layer is 800-1000°C; In step (5), the growth temperature of the high temperature p-type GaN layer is 850-1050° C., and the growth pressure is 100-500 torr; In step (5), the growth temperature of the p-type InGaN contact layer is 650-750° C., and the growth pressure is 200-400 torr.

Images