A UV light-emitting diode with an AlInGaN insertion layer

Abstract

The present invention provides an ultraviolet light-emitting diode (UV-LED) with an AlInGaN insertion layer, and its constituent elements successively include, from bottom to top: a substrate, an AlN nucleation layer, an AlN buffer layer, an undoped AlGaN buffer layer, an n-type AlGaN layer, Al x Ga 1‑x N / Al y Ga 1‑y N multiple quantum well active region and a p-type AlGaN layer. A p-type ohmic electrode and an n-type ohmic electrode are respectively led out on the p-type AlGaN layer and the n-type AlGaN layer. An AlInGaN insertion layer with a higher bandgap than the QB but the same lattice constant as the QB is inserted in the middle of the last Al y Ga 1‑y N quantum barrier (QB) to replace the traditional electron blocking layer (EBL). The UV-LED adopting the AlInGaN insertion layer can convert the hole depletion layer caused by the polarization field at the interface between the last QB and the EBL into a hole accumulation layer, improving the hole injection efficiency. At the same time, it can effectively reduce the band bending between the last QB and the p-type region, improve the overlap degree of the electron and hole wave functions, and it is easier to confine the electrons in the active region, thereby enhancing the radiative recombination of carriers and ultimately improving the internal quantum efficiency of the UV-LED.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor optoelectronic devices, and in particular relates to an ultraviolet light emitting diode (UV-LED) with an AlInGaN insertion layer. Background Art

[0002] Due to its high photon energy and strong penetrating power, ultraviolet light is widely used in sterilization, water and air purification, solid-state lighting, detection of biochemical hazardous substances, high-density storage and military communications.

[0003] AlGaN material is the core material for preparing UV-LED. Firstly, Al x Ga 1-x N material is a wide bandgap direct bandgap semiconductor material. By adjusting the Al component in the ternary compound AlGaN, the AlGaN bandgap energy can be continuously changed between 3.4 and 6.2 eV, thereby obtaining ultraviolet light with a wavelength range from 200 to 365 nm. x Ga 1-x N is a compound with strong ionic bonding, which has high thermal stability, chemical stability and long life. In addition, AlGaN-based UV-LED has low energy consumption and zero pollution, which has significant advantages over traditional gas UV light sources such as mercury lamps and xenon lamps, and has broad application prospects and great research value.

[0004] However, the internal quantum efficiency (IQE) of existing AlGaN-based UV-LEDs is still very low, and their layer structures such as Figure 2 As shown in the figure, the IQE decreases significantly with the increase of the injected current, which is the problem of efficiency droop. One of the main reasons for the IQE of UV-LED is the low efficiency of carrier radiation recombination in MQWs. Since the lattice constants of the materials of each layer of UV-LED are not the same, there is a spontaneous polarization electric field and a piezoelectric polarization electric field with an intensity of up to MV / cm inside the UV-LED, which will cause the energy band of MQWs to bend, the wave functions of electrons and holes to separate in space, and the recombination efficiency of electrons and holes to drop seriously, which ultimately leads to a decrease in the IQE of UV-LED. At the same time, due to the asymmetric transport performance of electrons and holes, a large number of electrons leak from the MQWs region to the p-type region, resulting in non-radiative recombination of electrons and holes in the p-type region, which in turn causes a decrease in the radiation recombination efficiency and a decrease in IQE.

[0005] To reduce electron leakage, a p-type electron blocking layer (EBL) with a higher barrier height than the quantum barrier (QB) is usually added between the last layer of the quantum barrier in the UV-LED and the p-type region. However, due to the positive surface charge caused by the polarization field at the interface between the last layer of the quantum barrier and the EBL, holes are depleted at the interface, resulting in a significant reduction in the hole injection efficiency. At the same time, the activation energy of the p-EBL with a higher Al component is very high, and it is very difficult to obtain an AlGaN electron blocking layer with a high hole concentration. This reduces the hole injection efficiency while effectively blocking electrons, resulting in a limited improvement in the internal quantum efficiency (IQE) of the UV-LED. Therefore, to improve the IQE of the UV-LED, the industry urgently needs to develop a new type of semiconductor UV-LED structure. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a UV-LED that uses an AlInGaN insertion layer instead of the traditional EBL. Compared with the traditional AlGaN-based UV-LED using EBL, this structure can convert the hole depletion layer caused by the polarization field at the interface between the last layer of the QB and the EBL into a hole accumulation layer, improving the hole injection efficiency. At the same time, replacing the EBL with an AlInGaN insertion layer can effectively reduce the band bending between the last layer of the QB and the p-type region, improve the overlap degree of the electron and hole wave functions, and more easily confine electrons in the active region, thereby enhancing the radiative recombination of carriers and ultimately improving the internal quantum efficiency of the UV-LED.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An ultraviolet light-emitting diode with an AlInGaN insertion layer, characterized in that it includes a substrate, an AlN nucleation layer, an AlN buffer layer, an undoped AlGaN buffer layer, an n-type AlGaN layer, Al x Ga 1-x N / Al y Ga 1-y N multiple quantum well active region, an Al p In q Ga 1-p-q N insertion layer, and a p-type AlGaN layer, which are sequentially arranged from bottom to top. A p-type ohmic electrode is led out from the p-type AlGaN layer, and an n-type ohmic electrode is led out from the n-type AlGaN layer. The Al p In q Ga 1-p-q N insertion layer is inserted between the last layer of the Al x Ga 1-x N / Al y Ga 1-y N multiple quantum well active region and the p-type AlGaN layer. y Ga 1-yIn the middle of the N quantum barrier.

[0009] To optimize the above technical solutions, the specific measures taken also include:

[0010] Further, the substrate is sapphire, silicon carbide, silicon, zinc oxide, gallium nitride or aluminum nitride with polar, semi-polar or non-polar orientation.

[0011] Further, the thickness of the AlN nucleation layer is 15 - 50 nm, the thickness of the AlN buffer layer is 50 - 500 nm, the thickness of the undoped AlGaN buffer layer is 500 - 2000 nm, the thickness of the n-type AlGaN layer is 200 - 5000 nm, Al x Ga 1-x N / Al y Ga 1-y The well width of the Al x Ga 1-x N quantum well in the Al y Ga 1-y N multi-quantum well active region is 1 - 10 nm, the barrier thickness of the Al

[0012] Further, the thickness of the Al p In q Ga 1-p-q N insertion layer is 1 - 10 nm.

[0013] Further, the bandgap of the Al p In q Ga 1-p-q N insertion layer is greater than the bandgap of the Al y Ga 1-y N quantum barrier.

[0014] Further, the lattice constant of the Al p In q Ga 1-p-q N insertion layer is the same as that of the Al y Ga 1-y N quantum barrier.

[0015] Further, the materials of the p-type ohmic electrode and the n-type ohmic electrode are one kind of metal among Ni, Al, Au or Ti or an alloy material composed of multiple above metals.

[0016] The beneficial effects of the present invention are as follows: The present invention provides a UV-LED with an AlInGaN insertion layer. By using an AlInGaN quantum well insertion layer to replace the traditional EBL, the positive polarization charge generated due to lattice mismatch between the last quantum barrier and the EBL can be eliminated, turning the original hole depletion region into a hole accumulation region and improving the hole injection efficiency. At the same time, by using an AlInGaN insertion layer to replace the EBL, the energy band bending between the last QB and the p-type region can be effectively reduced, improving the overlap degree of the electron and hole wave functions, and making it easier to confine electrons in the active region, thereby enhancing the radiative recombination of carriers and ultimately greatly improving the IQE of the UV-LED. Therefore, it is of great significance for improving the luminous power of the LED. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. is a schematic diagram of the layer structure of a UV-LED with an AlInGaN insertion layer.

[0018] Figure 2 FIG. is a schematic diagram of the layer structure of a UV-LED prepared by the prior art.

[0019] Figure 3a FIG. is a schematic diagram of the comparison of the output power of a UV-LED with an AlInGaN insertion layer and a UV-LED with a traditional EBL.

[0020] Figure 3b FIG. is a schematic diagram of the comparison of the IQE of a UV-LED with an AlInGaN insertion layer and a UV-LED with a traditional EBL.

[0021] The reference numerals are as follows:

[0022] 101 - Substrate; 102 - AlN nucleation layer; 103 - AlN buffer layer; 104 - Undoped AlGaN buffer layer; 105 - n-type AlGaN layer; 106 - Al x Ga 1-x N / Al y Ga 1-y N multiple quantum well active region; 107 - Al p In q Ga 1-p-q N insertion layer; 108 - p-type AlGaN layer; 109 - p-type ohmic electrode; 110 - n-type ohmic electrode;

[0023] 201 - Sapphire substrate; 202 - AlN nucleation layer; 203 - AlN buffer layer; 204 - Undoped AlGaN buffer layer; 205 - n-type AlGaN layer; 206 - Al x Ga 1-x N / Al y Ga 1-yN multi-quantum well active region; 207- AlGaN electron blocking layer; 208- p-type AlGaN layer; 209- p-type ohmic electrode; 210- n-type ohmic electrode. DETAILED DESCRIPTION

[0024] The present invention will now be described in further detail with reference to the accompanying drawings.

[0025] like Figure 1 As shown, a UV-LED with an AlInGaN insertion layer structure includes a substrate 101, an AlN nucleation layer 102, an AlN buffer layer 103, a non-doped AlGaN buffer layer 104, an n-type AlGaN layer 105, an Al x Ga 1-x N / A y Ga 1-y N multi-quantum well active region 106, inserted in the last layer of Al y Ga 1-y Al in the middle of N quantum barrier p In q Ga 1-p-q An N-insertion layer 107 and a p-type AlGaN layer 108 , a p-type ohmic electrode 109 is drawn out on the p-type AlGaN layer 108 , and an n-type ohmic electrode 110 is drawn out on the n-type AlGaN layer 105 , wherein y>x.

[0026] In some embodiments, substrate 101 is an r-plane semi-polar oriented sapphire substrate.

[0027] In some embodiments, the thickness of the AlN nucleation layer 102 is 20 nm, the thickness of the AlN buffer layer 103 is 103-200 nm, the thickness of the undoped AlGaN buffer layer 104 is 500 nm, the thickness of the n-type AlGaN layer 105 is 300 nm, and the thickness of the AlN buffer layer 103 is 103-200 nm. 0.45 Ga 0.55 N / A 0.6 Ga 0.4 N multi-quantum well active region 106 Al 0.45 Ga 0.55 The width of the N quantum well is 3 nm, and the Al 0.6 Ga 0.4 The thickness of the N barrier is 8 nm, the number of periods is 5, and the thickness of the p-type AlGaN layer 108 is 100 nm.

[0028] In some embodiments, the last layer of Al 0.6 Ga 0.4 Al is inserted in the middle of N quantum barrier 0.73 In 0.03 Ga 0.24 N insertion layer 107. Al 0.73In 0.03 Ga 0.24 The bandgap of GaN is larger than that of Al 0.6 Ga 0.4 N quantum barrier, and the lattice constant of Al 0.73 In 0.03 Ga 0.24 N is the same as that of Al 0.6 Ga 0.4 N quantum barrier.

[0029] Specifically, the present invention simulates and compares the luminous power and internal quantum efficiency of a UV-LED with an AlInGaN insertion layer structure adopting the above-mentioned implementation manner and a conventional UV-LED with an Al 0.7 Ga 0.3 N EBL before the last quantum barrier and the p-type AlGaN region. Among them, for the conventional UV-LED with an Al Figure 2 as shown 0.7 Ga 0.3 N EBL, the thickness of the AlGaN electron blocking layer 207 is 100 nm, and the remaining simulation parameters are the same as those of the above-mentioned implementation scheme. The specific simulation results are as shown in Figure 3a and 3b shown.

[0030] As can be seen from the figure, when the injection current is 200 mA, the luminous power and IQE of the UV-LED with an AlInGaN insertion layer are increased by 27.6% and 42.3% respectively compared with the conventional UV-LED with an EBL, which fully shows that replacing the conventional EBL with an AlInGaN insertion layer can improve the luminous performance of the UV-LED.

[0031] It should be noted that the terms such as "upper", "lower", "left", "right", "front", "rear", etc. cited in the invention are only for the convenience of description and are not used to limit the scope of implementation of the present invention. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope of implementation of the present invention.

[0032] The above is only the preferred implementation manner of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. An ultraviolet light-emitting diode with an AlInGaN insertion layer, characterized in that, The invention comprises a substrate (101), an AlN nucleation layer (102), an AlN buffer layer (103), a non-doped AlGaN buffer layer (104), an n-type AlGaN layer (105), and an Al x Ga 1-x N / A y Ga 1-y N multi-quantum well active region (106), Al p In q Ga 1-p-q N insertion layer (107) and p-type AlGaN layer (108), a p-type ohmic electrode (109) is drawn out from the p-type AlGaN layer (108), an n-type ohmic electrode (110) is drawn out from the n-type AlGaN layer (105), and the Al p In q Ga 1-p-q N insertion layer (107) is inserted in Al x Ga 1-x N / A y Ga 1-y The last layer of Al in the N multi-quantum well active region (106) y Ga 1-y N quantum barrier in the middle; the Al p In q Ga 1-p-q The bandgap of the N-insertion layer (107) is larger than that of the Al y Ga 1-y The bandgap width of the N quantum barrier; the Al p In q Ga 1-p-q The lattice constant of the N-insertion layer (107) and Al y Ga 1-y The lattice constants of the N quantum barriers are the same.

2. The ultraviolet light-emitting diode with an AlInGaN insertion layer as described in claim 1, characterized in that: The substrate (101) is sapphire, silicon carbide, silicon, zinc oxide, gallium nitride or aluminum nitride with polar, semi-polar or non-polar orientation.

3. The ultraviolet light-emitting diode with an AlInGaN insertion layer according to claim 1, characterized in that: The thickness of the AlN nucleation layer (102) is 15 - 50 nm, the thickness of the AlN buffer layer (103) is 50 - 500 nm, the thickness of the undoped AlGaN buffer layer (104) is 500 - 2000 nm, the thickness of the n-type AlGaN layer (105) is 200 - 5000 nm, Al x Ga 1-x N / Al y Ga 1-y The well width of the Al x Ga 1-x N quantum well in the N multi-quantum well active region (106) is 1 - 10 nm, the barrier thickness of the Al y Ga 1-y N quantum barrier is 4 - 30 nm, the number of periods is 3 - 50, the thickness of the p-type AlGaN layer (108) is 50 - 500 nm, and the Al composition relationship satisfies x < y.

4. The ultraviolet light-emitting diode with an AlInGaN insertion layer as described in claim 1, wherein: The Al p In q Ga 1-p-q The thickness of the InGaN insertion layer (107) is 1 - 10 nm.

5. The ultraviolet light-emitting diode with an AlInGaN insertion layer as described in claim 1, characterized in that: The materials of the p-type ohmic electrode (109) and the n-type ohmic electrode (110) are one of the metals Ni, Al, Au or Ti or an alloy material composed of multiple of the above metals.

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