Gallium nitride-based light emitting diode epitaxial structure with tunnel junction and preparation method of gallium nitride-based light emitting diode epitaxial structure

Abstract

The invention discloses a gallium nitride-based light emitting diode epitaxial structure with a tunnel junction and a preparation method thereof, and belongs to the technical field of semiconductor manufacturing. The structure sequentially comprises a gallium nitride-based light emitting diode, an AlGaInN porous layer, a second n-type semiconductor layer and a third n-type semiconductor layer from bottom to top. In-situ treatment is carried out on the p-type semiconductor layer on the surface of the gallium nitride-based light emitting diode, surface pollutants are removed to avoid the influence of the Mg memory effect, and the steepness of the doping concentration of the tunnel junction interface is improved; the porous layer is introduced to connect the p-type semiconductor layer and the second n-type semiconductor layer, on one hand, interfaces on two sides can be ensured to be clear, the problem that Mg-Si compensation introduces high resistance is avoided, on the other hand, the porous structure is beneficial to the formation of ohmic contact, the transverse conductivity of the tunnel junction can be improved, and the voltage drop can be effectively reduced; and effective stacking connection of a red / green / blue GaN-based light emitting diode or other GaN-based photoelectric devices is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and particularly relates to a gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction and a preparation method thereof. Background Art

[0002] As the core technology of third-generation semiconductor devices, gallium nitride (GaN)-based tunnel junctions play a crucial role in optoelectronic fields such as light-emitting diodes (LEDs) and lasers. Especially in LED applications, using a tunnel junction to replace the traditional ITO layer can not only effectively achieve current spreading but also significantly reduce light absorption losses, thereby improving the efficiency of the device. In addition, since the tunnel junction has the same GaN material system as the LED, multiple LEDs can be integrated through a single epitaxial growth process, or it can be stacked with other GaN-based optoelectronic devices. This design greatly simplifies the process flow and reduces production costs, having broad application prospects and economic benefits.

[0003] The basic working principle of the tunnel junction is to utilize the heavily doped np junctions on both sides. Under reverse bias, the quantum tunneling effect occurs. The valence band of the heavily doped p side is higher than the conduction band of the heavily doped n side, and electrons can tunnel from the p side to the n side, generating a high-density tunneling current. The commonly used growth methods for tunnel junctions include MBE, MOCVD, and hybrid growth of MBE + MOCVD. Research reports so far show that the tunnel junction with the lowest voltage drop is obtained by MBE growth. However, the MBE equipment cost is high and it is difficult to achieve commercialization. Compared with MBE, the more popular MOCVD is a commercial device commonly used for nitride materials. But for MOCVD, due to the H-rich environment in the chamber and the memory effect of Mg, most of the Mg in p-GaN exists in the form of Mg-H complexes, making it difficult to achieve effective Mg doping to provide a high concentration of holes, ultimately resulting in a high voltage drop. Although annealing is carried out to activate after etching the mesa in the chip manufacturing process, the top n-GaN blocks part of the escape path, weakening the annealing effect. On the other hand, when the heavily doped p and heavily doped n are in contact, there is a Mg-Si compensation effect, further increasing the resistance of the tunnel junction and making it difficult to achieve effective current spreading. Summary of the Invention

[0004] Object of the Invention: The first object of the present invention is to provide a gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction that has a simple preparation process, low cost, and can achieve effective current spreading. This structure can promote the Mg activation of p-GaN, improve the contact, enhance the current spreading ability, and achieve a tunnel junction with a low voltage drop. The second object of the present invention is to provide a preparation method for the above-mentioned gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction, which can alleviate the memory effect of Mg and improve the interface quality.

[0005] Technical solution: The gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction includes, from bottom to top, a gallium nitride-based light-emitting diode, an AlGaInN porous layer, a second n-type semiconductor layer, and a third n-type semiconductor layer.

[0006] Further, the cross-section of the nanopores in the AlGaInN porous layer is uniformly distributed or disorderly distributed perpendicular to the surface of the epitaxial wafer; the thickness of the second n-type semiconductor layer is 1 - 50 nm, and the Si doping concentration > 5×10 19 cm -3 ; the thickness of the third n-type semiconductor layer is 50 - 1000 nm, and the Si doping concentration > 1×10 19 cm -3 .

[0007] Further, the gallium nitride-based light-emitting diode includes, from bottom to top, a growth substrate, a buffer layer, a first n-type semiconductor layer, a multi-quantum well active layer, a first p-type semiconductor layer, an electron blocking layer, a second p-type semiconductor layer, and a third p-type semiconductor layer.

[0008] Further, the growth substrate includes sapphire, silicon carbide, silicon, diamond, gallium nitride, aluminum nitride, or gallium oxide; the buffer layer is a combination of one or more of AlGaN, AlN, and GaN, the growth temperature is 700 - 1100 °C, and the thickness is 500 - 5000 nm.

[0009] Further, the thickness of the first n-type semiconductor layer is 100 - 5000 nm, and the Si doping concentration is 1×10 15 -1×10 21 cm -3 ; the material of the multi-quantum well active layer is Al x In y Ga 1-x-y N / Al x1 In y1 Ga 1-x1-y1 N-based material, where 0 ≤ x / y ≤ 1, 0 ≤ x1 / y1 ≤ 1, the thicknesses of the single-layer quantum well and the quantum barrier are 1 - 10 nm / 1 - 20 nm respectively, and it contains 1 - 10 quantum wells, and the growth temperature is 650 - 900 °C.

[0010] Further, the material of the first p-type semiconductor layer is Al x In y Ga 1-x-y N, 0 ≤ x / y < 1 - x - y ≤ 1, the growth temperature is 600 - 900 °C, the thickness is 5 - 500 nm, and the Mg doping concentration is 1×10 15 -1×10 21 cm -3 .

[0011] Furthermore, the material of the electron blocking layer is Al x Ga 1-x N / Al y Ga 1-y N-based material, where 0 ≤ x < y ≤ 1, the Al component is higher than that of the quantum barrier, and it can be grown by a multi-segment pulse method with a gradually changing Al component, at a temperature of 800 - 1100 °C and a thickness of 10 - 500 nm to prevent electron overshoot.

[0012] Furthermore, the material of the second p-type semiconductor layer is Al x Ga 1-x N, 0 ≤ x < y ≤ 1, the growth temperature is 800 - 1100 °C, the thickness is 5 - 500 nm, and the Mg doping concentration is 1×10 15 -1×10 21 cm -3 .

[0013] Furthermore, the material of the third p-type semiconductor layer is Al x Ga 1-x N, 0 ≤ x < y ≤ 1, the growth temperature is 800 - 1100 °C, the thickness is 1 - 100 nm, and the Mg doping concentration is 1×10 19 -1×10 22 cm -3 .

[0014] The present invention also provides a method for preparing the above-mentioned gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction, including the following steps:

[0015] (1) Prepare a gallium nitride-based light-emitting diode;

[0016] (2) Perform in-situ surface treatment on the gallium nitride-based light-emitting diode, and then epitaxially grow Al x In y Ga 1-x-y N porous pre-layer, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 < x + y < 1;

[0017] (3) Perform in-situ treatment or ex-situ treatment on the Al x In y Ga 1-x-y N porous pre-layer to achieve a porous structure, and obtain an AlGaInN porous layer;

[0018] (4) Epitaxially grow a second n-type semiconductor layer on the AlGaInN porous layer;

[0019] (5) Epitaxially grow a third n-type semiconductor layer on the second n-type semiconductor layer to obtain a gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction.

[0020] Furthermore, in step (1), the method for preparing a gallium nitride-based light-emitting diode includes the following steps:

[0021] S1. Prepare a growth substrate;

[0022] S2. Epitaxially grow a buffer layer on the upper side of the above-mentioned substrate;

[0023] S3. Epitaxially grow a first n-type semiconductor on the above-mentioned buffer layer;

[0024] S4. Epitaxially grow a multi-quantum well active layer on the above-mentioned first n-type semiconductor layer;

[0025] S5. Epitaxially grow a first p-type semiconductor layer on the multi-quantum well active layer;

[0026] S6. Epitaxially grow an electron blocking layer on the above-mentioned first p-type semiconductor layer;

[0027] S7. Epitaxially grow a second p-type semiconductor layer on the above-mentioned electron blocking layer;

[0028] S8. Epitaxially grow a third p-type semiconductor layer on the above-mentioned second p-type semiconductor layer.

[0029] Furthermore, in step (2), the in-situ surface treatment method is as follows: A mixed gas of NH3, H2, N2, TBCl3 alone or in combination is introduced into the growth chamber in a continuous or staged pulse manner. At a growth temperature of 700 - 1000 °C, the chamber pressure is 50 - 200 torr, and in-situ thermal annealing is performed for 30 s - 30 min.

[0030] Furthermore, in step (2), when growing the Al x In y Ga 1-x-y N porous preparatory layer, SiH4 is introduced for doping in a continuous or pulsed manner, or co-doping with Mg and Si in a δ-distributed doping form is performed, with a thickness of 1 - 5 nm and a doping concentration of 1×10 17 -1×10 20 cm -3 ^-3^, or a single layer or multiple layers of Al x In y Ga 1-x-y N / GaN are grown, with a thickness of 1 - 5 nm.

[0031] Further, in step (3), the in-situ treatment method is as follows: introducing a combination or single gas of NH3, H2, N2, and TBCl3, with a temperature of 500 - 1000 °C, a time of 30 s - 30 min, and a pore size of 5 - 500 nm. The size, density, and morphology of the pores can be regulated by adjusting the treatment atmosphere, gas flow rate, temperature, pressure, and time. The ex-situ treatment method is as follows: obtained by electrochemical corrosion, photoelectrochemical corrosion, or photocatalytic corrosion of n- or p-type doped or undoped Al x In y Ga 1-x-y N method, and the electrolyte solution used is an acidic, alkaline solution, or a mixed solution with other salt solutions; such as KOH, AZ400K, NaOH, HNO3, HF, H2SO4, HCl, H2C2O4, H3PO4. Among them, the power supply used for electrochemical corrosion and photoelectrochemical corrosion is a DC power supply, and the corrosion voltage is 5 - 100 V.

[0032] Further, in steps (4) - (5), the epitaxial growth method is MOCVD, MBE, or a combination of both.

[0033] Principle of the invention: The present invention proposes an epitaxial structure of a gallium nitride-based light-emitting diode with a tunnel junction. The in-situ surface treatment can reduce the Mg compensation effect, increase the steepness of the doping concentration change at the interface, and obtain a clear interface. In addition, the porous layer in this structure can not only promote the escape of H in p-GaN but also improve the contact and enhance the current spreading ability. The epitaxial structure and its preparation method of the present invention are simpler than the conventional tunnel junction epitaxial technologies, with lower process and time costs.

[0034] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The preparation process of the present invention is simple and low in cost; (2) By in-situ treating the third p-type semiconductor layer, the present invention can effectively remove the Mg-related residues on the surface, facilitate the formation of a clear and flat interface, reduce the Mg compensation effect, increase the steepness of the doping concentration change at the interface, avoid secondary pollution of the interface by ex-situ treatment, and at the same time reduce the process and time costs; (3) During the high-temperature growth of the second and third n-type semiconductors, In will precipitate in the pores of the underlying porous Al x In y Ga 1-x-y N layer. The contact between In and p-GaN easily forms an ohmic contact, which can promote current spreading, improve the contact, and reduce the voltage drop. In addition, the porous structure is also beneficial for the escape of H in p-GaN during subsequent annealing; (4) During the growth of Al x In y Ga 1-x-yDoping is carried out during the preparation of the N-porous pre-layer, which is beneficial to the formation of the porous structure, reduces the contact resistance, and increases the tunneling probability; (5) Al in the present invention x In y Ga 1-x-y AlGaInN / GaN can be regulated by energy band engineering to reduce the tunneling barrier, generate polarization charges, and increase the tunneling probability. Description of the Drawings

[0035] Figure 1 is a schematic structural diagram of a GaN-based light-emitting diode epitaxial structure with a tunnel junction in Example 1;

[0036] Figure 2 is a top view of the pores of the AlGaInN porous layer in Example 1;

[0037] Figure 3 is a process flow chart for the preparation of a GaN-based light-emitting diode epitaxial structure with a tunnel junction in Example 1. Detailed Embodiments

[0038] Next, the present invention will be further described in conjunction with specific embodiments and the accompanying drawings.

[0039] Example 1: As Figure 1 shown, the GaN-based light-emitting diode epitaxial structure with a tunnel junction provided in this embodiment sequentially includes, from bottom to top: a GaN-based light-emitting diode, an AlGaInN porous layer 109, a second n-type semiconductor layer 110, and a third n-type semiconductor layer 111; wherein, the GaN-based light-emitting diode sequentially includes, from bottom to top: a growth substrate 101, a buffer layer 102, a first n-type semiconductor layer 103, a multi-quantum well active layer 104, a first p-type semiconductor layer 105, an electron blocking layer 106, a second p-type semiconductor layer 107, and a third p-type semiconductor layer 108.

[0040] As Figure 2 shown, the cross-section of the nanopores in the AlGaInN porous layer 109 is uniformly distributed 1092 or disorderly distributed 1091 perpendicular to the surface of the epitaxial wafer.

[0041] As Figure 3 shown, the preparation method steps of the above-mentioned GaN-based light-emitting diode epitaxial structure with a tunnel junction are as follows:

[0042] (1) Prepare a GaN-based light-emitting diode, and the steps are as follows:

[0043] S1: Use MOCVD to grow a GaN-based buffer layer 102, a first n-type semiconductor layer 103, an active layer 104, a first p-type semiconductor layer 105, an electron blocking layer 106, a second p-type semiconductor layer, and a third p-type semiconductor layer on the sapphire substrate 101. The specific growth conditions of the step S1 are as follows:

[0044] S101: Growth of buffer layer 102; The epitaxial buffer layer 102 is AlN, the growth temperature is 800 °C, and the thickness is 30 nm;

[0045] S102: First n-type semiconductor layer 103, at 1000 - 1200 °C, introducing TMGa, NH3, SiH4, N2, H2, growing GaN with a thickness of 5000 nm, and the Si doping concentration is 2×10 19 cm -3 ;

[0046] S103: Multiple quantum well active layer 104, at 700 - 900 °C, introducing TEGa, TMIn, TMAl, NH3, SiH4, N2, H2, growing, which is composed of an alternating barrier layer, capping layer and well layer. The barrier layer is GaN with a thickness of 15 nm, the capping layer is Al 0.1 Ga 0.9 N with a thickness of 1 - 2 nm, the well layer is In 0.2 Ga 0.8 N with a thickness of 2.5 - 3.5 nm, and the number of pairs is 9;

[0047] S104: First p-type semiconductor layer 105, at 700 - 900 °C, introducing TEGa, TMIn, TMAl, NH3, Cp2Mg, N2, H2, and its material is Al 0.02 In 0.03 Ga 0.95 N with a thickness of 20 - 50 nm, and the Mg doping concentration is 1×10 20 cm -3 ;

[0048] S105: Electron blocking layer 106, at 900 - 1100 °C, using Al 0.4 Ga 0.6 N as the barrier and GaN as the well, growing 6 pairs in a cycle with thicknesses of 2 nm and 1 nm respectively, then using Al 0.2 Ga 0.8 N as the barrier and GaN as the well, growing 3 pairs in a cycle with thicknesses of 2 nm and 1 nm respectively, then using Al 0.1 Ga 0.9 N as the barrier and GaN as the well, growing 3 pairs in a cycle with thicknesses of 2 nm and 1 nm respectively, and the total thickness is 36 nm;

[0049] S106: Second p-type semiconductor layer 107, at 900 - 1000 °C, introducing TEGa, NH3, Cp2Mg, N2, H2, and its material is GaN with a thickness of 2 - 50 nm, and the Mg doping concentration is 5×10 19 cm -3 ;

[0050] S107: The third p-type semiconductor layer 108, at a temperature of 900 - 1100 °C, TEGa, NH3, Cp2Mg, N2, and H2 are introduced. Its material is GaN, with a thickness of 1 - 20 nm and an Mg doping concentration of 1×10 21 cm -3 ;

[0051] (2) Perform in-situ surface treatment on the gallium nitride-based light-emitting diode. A mixed gas of NH3 and TBCl3 is introduced into the growth chamber at a temperature of 700 - 900 °C and a chamber pressure of 200 torr, followed by in-situ thermal annealing for 5 min; then, using MOCVD, an AlGaInN porous pre-layer is epitaxially grown on the above-mentioned surface-treated GaN-based LED;

[0052] When growing Al 0.2 In 0.2 Ga 0.6 N, SiH4 is introduced in a pulsed manner for doping, with a thickness of 1 - 5 nm and a doping concentration of 1×10 20 cm -3 , and the temperature is 700 - 900 °C.

[0053] (3) Perform in-situ treatment on the above-mentioned AlGaInN porous pre-layer to achieve a porous structure. This layer can be a structural layer 1092 with a porous direction showing uniform distribution perpendicular to the surface of the epitaxial wafer, or a structural layer 1091 with porous disordered distribution;

[0054] During in-situ treatment, a mixed gas of NH3, H2, and TBCl3 is introduced at a temperature of 700 - 900 °C for 10 min, and the pore size is 50 - 200 nm.

[0055] (4) Using MOCVD, epitaxially grow a second n-type semiconductor layer 110 and a third n-type semiconductor layer 111 on the above-mentioned AlGaInN porous layer 109:

[0056] First, epitaxially grow a second n-type semiconductor layer 110 on the AlGaIn porous layer 109. At a temperature of 600 - 800 °C, TMGa, NH3, Cp2Mg, N2, and H2 are introduced. Its material is GaN, with a thickness of 1 - 20 nm, growth temperature, and Si doping concentration of 1×10 21 cm -3 ;

[0057] Epitaxially grow a third n-type semiconductor n-GaN layer 111 on the second n-type semiconductor layer 110. At a temperature of 1000 - 1200 °C, TMGa, NH3, SiH4, N2, and H2 are introduced to grow GaN with a thickness of 500 nm and an Si doping concentration of 2×10 19 cm -3, ensure a flat surface is formed, a good ohmic contact is formed, while protecting the underlying tunnel junction, which is beneficial to the subsequent integration with other optoelectronic devices.

[0058] In the present invention, through the in-situ surface treatment of the p-GaN layer, surface Mg-related complexes can be effectively removed, providing a flat surface for further n-GaN, improving the interface clarity, facilitating the formation of a steep doping concentration gradient, and alleviating the Mg-Si compensation effect. In addition, an AlInGaN porous structure is introduced into the tunnel junction. On the one hand, at high temperatures, the precipitated In in the pores is beneficial to the formation of ohmic contact, promotes current spreading, and enhances the lateral conductivity. On the other hand, the porous structure is conducive to the escape of H during the subsequent annealing process of p-GaN, improving the activation efficiency of Mg, solving the problem of high voltage drop of the existing MOCVD epitaxial GaN-based tunnel junction, and at the same time avoiding the problem of light absorption after introducing an InGaN insertion layer. Therefore, these advantages provided by the present invention are of great significance for the preparation of high quantum efficiency GaN-based LEDs and the realization of the stacking of high-efficiency GaN-based optoelectronic devices.

[0059] Example 2: The difference from Example 1 is that in step (3), an ex-situ treatment is used to prepare the porous structure.

[0060] For ex-situ treatment, after in-situ treatment, the GaN-based LED epitaxial wafer is taken out of the chamber, and a KOH solution is used to electrochemically etch the AlGaInN porous pre-layer into a porous structure by applying a DC voltage of 10 V, and the pore size is 10 - 500 nm.

[0061] In this embodiment, through the ex-situ treatment of the AlGaInN porous pre-layer, the preparation of the porous structure can be realized quickly and controllably. This porous structure can not only improve the contact characteristics through the precipitation of In at high temperatures, but also improve the heat dissipation capacity of the device, which is beneficial to the preparation of high-performance GaN-based LEDs.

Claims

1. A gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction, characterized in that: It includes, from bottom to top, a gallium nitride-based light-emitting diode, an AlGaInN porous layer, a second n-type semiconductor layer and a third n-type semiconductor layer.

2. The gallium nitride-based light-emitting diode epitaxial structure with tunnel junction according to claim 1, characterized in that: The cross section of the nanopores in the AlGaInN porous layer is uniformly distributed or disorderly distributed perpendicular to the surface of the epitaxial wafer; the thickness of the second n-type semiconductor layer is 1-50nm, and the Si doping concentration is>5×10 19 cm -3 The thickness of the third n-type semiconductor layer is 50-1000nm, and the Si doping concentration is >1×10 19 cm -3 .

3. The GaN-based light-emitting diode epitaxial structure with tunnel junction according to claim 1, characterized in that: The gallium nitride-based light-emitting diode comprises, from bottom to top, a growth substrate, a buffer layer, a first n-type semiconductor layer, a multi-quantum well active layer, a first p-type semiconductor layer, an electron blocking layer, a second p-type semiconductor layer, and a third p-type semiconductor layer.

4. The GaN-based light-emitting diode epitaxial structure with tunnel junction according to claim 3, characterized in that: The growth substrate includes sapphire, silicon carbide, silicon, diamond, gallium nitride, aluminum nitride or gallium oxide.

5. The GaN-based light-emitting diode epitaxial structure with tunnel junction according to claim 3, characterized in that: The material of the third p-type semiconductor layer is Al x Ga 1-x N, where 0 ≤ x < y ≤ 1, the growth temperature is 800 - 1100 °C, the thickness is 1 - 100 nm, and the Mg doping concentration is 1×10 19 -1×10 22 cm -3 .

6. A method for preparing a gallium nitride-based light-emitting diode epitaxial structure with a tunnel junction according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Preparing gallium nitride-based light-emitting diodes; (2) In-situ surface treatment of GaN-based light-emitting diodes and epitaxial growth of Al x In y Ga 1-x-y N porous preparatory layers, where 0≤x≤1, 0≤y≤1, 0 <x+y<1; (3) Al x In y Ga 1-x-y The N porous preparatory layer is processed in situ or ex situ to realize a porous structure, thereby obtaining an AlGaInN porous layer; (4) epitaxially growing a second n-type semiconductor layer on the AlGaInN porous layer; (5) epitaxially growing a third n-type semiconductor layer on the second n-type semiconductor layer, thereby obtaining a gallium nitride-based light-emitting diode epitaxial structure having a tunnel junction.

7. The preparation method according to claim 6, characterized in that: In step (2), the in-situ surface treatment method is: a single or combined mixed gas of NH3, H2, N2, and TBCl3 is introduced into the growth chamber in a continuous or staged pulse manner, at a growth temperature of 700-1000°C, a chamber pressure of 50-200torr, and in-situ thermal annealing for 30s-30min.

8. The preparation method according to claim 6, characterized in that: In step (2), during the growth of Al x In y Ga 1-x-y N porous preparatory layer, SiH4 is introduced continuously or in pulses for doping, or Mg and Si are co-doped in a delta distribution, with a thickness of 1-5 nm and a doping concentration of 1×10 17 -1×10 20 cm -3 , or grow single or multilayer Al x In y Ga 1-x-y N / GaN, thickness is 1-5nm.

9. The preparation method according to claim 6, characterized in that: In step (3), the in-situ treatment method is: introducing a combination of NH3, H2, N2, TBCl3 or a single gas at a temperature of 500-1000°C for 30s-30min, with a pore size of 5-500nm; the ex-situ treatment method is: electrochemical corrosion, photoelectrochemical corrosion or photocatalytic corrosion of n- or p-type doped or non-doped Al x In y Ga 1-x-y N method is used, the electrolyte solution used is an acidic solution, an alkaline solution or a mixture with other salt solutions; wherein the power source used for electrochemical corrosion and photoelectrochemical corrosion is a direct current power source, and the corrosion voltage is 5-100V.

10. The preparation method according to claim 6, characterized in that: In step (4) to step (5), the epitaxial growth method is MOCVD, MBE or a mixture of the two.

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