Blue-green double-peak LED epitaxial growth method

Abstract

The invention is suitable for the technical field of semiconductors, and provides a blue-green double-peak LED epitaxial growth method, which comprises the following steps: processing a substrate, growing a low-temperature GaN buffer layer, growing a non-doped GaN layer, growing a Si-doped N-type GaN layer, growing a multi-quantum well layer, growing an AlGaN electron barrier layer, growing a Mg-doped P-type GaN layer, and cooling. Wherein the growth of the multi-quantum well layer sequentially comprises the steps of growing a first MQWs, growing a tunnel junction layer, growing a second MQWs and growing an AlGaN / GaN superlattice layer, the tunnel junction layer is introduced into the multi-quantum well layer to enhance tunneling of holes, meanwhile, the AlGaN / GaN superlattice layer is introduced, gradual change of an Al component in AlGaN is controlled by controlling the introduction time of TMAl, the problem of light emitting peak broadening is solved, and the light emitting efficiency is improved. The quantum well is ensured to emit blue light and green light at the same time, the color saturation of the light is improved, and the color temperature is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, in particular to a blue-green double-peak LED epitaxial growth method. Background Art

[0002] A light-emitting diode (LED) is a semiconductor electronic device that converts electrical energy into light. When current flows through an LED, electrons and holes recombine within its quantum wells, emitting monochromatic light. As a highly efficient, environmentally friendly, and green new solid-state lighting source, LEDs have been widely used in indoor and outdoor lighting, mobile phone and television displays, traffic lights, and automotive lighting. Beyond lighting, LED applications have also expanded into various other fields, including sterilization, medical treatment, biomedicine, polymer printing, barcode verification, and optical sensors.

[0003] Currently, LEDs used in TV backlighting require dual-color light to enhance color saturation. However, existing methods for growing LED multi-quantum wells (MQWs) produce epitaxial InGaN / GaN MQWs that can only emit monochromatic wavelengths, such as blue (445-460nm) or green (500-560nm). The significant difference in energy barriers between blue and green light makes it difficult for quantum wells to emit both blue and green light simultaneously.

[0004] Therefore, in view of the above situation, there is an urgent need to provide a blue-green dual-peak LED epitaxial growth method to overcome the shortcomings in current practical applications. Summary of the Invention

[0005] The purpose of the present invention is to provide a blue-green dual-peak LED epitaxial growth method, aiming to solve the problems in the above-mentioned background technology.

[0006] The present invention is achieved by providing a blue-green dual-peak LED epitaxial growth method, the method comprising the following steps: Processing substrate, growing low-temperature GaN buffer layer, growing undoped GaN layer, growing Si-doped N-type GaN layer, growing multi-quantum well layer, growing AlGaN electron barrier layer, growing Mg-doped P-type GaN layer and cooling; The growing of the multi-quantum well layer comprises: The first MQWs are grown, a tunnel junction layer is grown, a second MQWs is grown, and an AlGaN / GaN superlattice layer is grown.

[0007] As a further solution of the present invention: the growth of the first MQWs is specifically as follows: First, a first InGaN well layer is grown, and then a first GaN barrier layer with a thickness of D1 is grown, and the growth of the first InGaN well layer and the first GaN barrier layer is repeated for 8 to 13 cycles; The In content in the first InGaN well layer is controlled to be 15-20%, and the first MQWs emit blue light.

[0008] As a further solution of the present invention: the growth tunnel junction layer is specifically: First, a Si-doped InGaN layer is grown, and then a Si-doped GaN layer is grown, and the sum of the thicknesses of the InGaN layer and the GaN layer is D2, and D2 is 0.3-0.5 times that of D1.

[0009] As a further solution of the present invention, the growth of the second MQWs is specifically as follows: First, a second InGaN well layer is grown, and then a second GaN barrier layer with a thickness of D1 is grown, and the growth of the second InGaN well layer and the second GaN barrier layer is repeated for 3-6 cycles; The In content in the second InGaN well layer is controlled to be 15-20%, and the In content in the second InGaN well layer is controlled to gradually increase from the first period to the last period, and the second MQWs emit green light.

[0010] As a further solution of the present invention: the first GaN barrier layer and the second GaN barrier layer are both doped with Si, and the Si doping concentration is 2E17-5E17.

[0011] As a further solution of the present invention: the growth of the AlGaN / GaN superlattice layer adopts a pulse growth method; During the growth process, NH3 and TMAl are both introduced in pulses, and the Al composition gradient in AlGaN is controlled by controlling the introduction time t of TMAl.

[0012] As a further solution of the present invention: the NH3 introduction and closing time are 1-2 seconds, the TMA1 closing time is 1-4 seconds, and the pulse period is 50-100; The TMAl introduction time t was controlled to decrease uniformly from 12 seconds to 2 seconds, so that the Al atomic molar content of the AlGaN layer was uniformly and gradually decreased from 20% to 6%.

[0013] As a further solution of the present invention: the value of D1 is 8-15nm.

[0014] As a further solution of the present invention: the Si doping concentration in the tunnel junction layer is 2E17-5E17.

[0015] As a further solution of the present invention, the In content is gradually increased during the growth of the second MQWs, specifically: The molar content of In atoms in the second InGaN well layer increases gradually from the first period to the last period at a ratio of 0.5% to 1.5%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention first grows a first MQW that can excite blue light, followed by a second MQW that can excite green light. Because the barrier of the green light well is significantly lower than that of the blue light well, and the hole mobility is only 1 / 10 of that of electrons, holes are easily confined in the green light well. The present invention enhances hole tunneling by introducing a tunnel junction layer between the first and second MQWs. The thickness of the tunnel junction layer is controlled to be between 0.3 and 0.5 times the thickness of the first and second GaN barrier layers. This reduces the barrier width, making it easier for holes to tunnel from the green light well to the blue light well. Furthermore, the hole tunneling time is made comparable to the carrier lifetime, thereby increasing the hole concentration in the blue light well and ensuring sufficient carrier recombination in both the first and second MQWs. Furthermore, doping the tunnel junction layer with Si increases carrier mobility, thereby improving radiative recombination efficiency and luminescence efficiency.

[0017] The thickness of the tunnel junction layer is relatively thin, which may cause coupling between quantum wells and lead to broadening of the luminescence peak. This application introduces an AlGaN / GaN superlattice layer in the multi-quantum well and controls the gradual change of the Al component in AlGaN by controlling the introduction time of TMAl to suppress wave function overlap and reduce coupling between quantum wells, thereby avoiding broadening of the luminescence peak and ensuring that the quantum well emits blue and green light at the same time. It can also improve the color saturation of the light and reduce the color temperature. The color saturation of the light can reach 98%, and the color temperature of the light can be as low as 2000K after chip packaging.

[0018] When growing the second MQWs, controlling the In content in the InGaN well layer to gradually increase can reduce the built-in electric field, pre-compensate lattice stress, relieve compressive strain, and effectively solve the band tilt problem caused by the piezoelectric polarization field, thereby improving the radiative recombination efficiency and the luminous efficiency of the LED. DETAILED DESCRIPTION

[0019] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0021] The present invention will be further explained below with reference to specific embodiments.

[0022] An embodiment of the present invention provides a blue-green dual-peak LED epitaxial growth method, which sequentially comprises: processing a substrate, growing a low-temperature GaN buffer layer, growing an undoped GaN layer, growing a Si-doped N-type GaN layer, growing a multi-quantum well layer, growing an AlGaN electron barrier layer, growing a Mg-doped P-type GaN layer, and cooling; wherein growing the multi-quantum well layer sequentially comprises: growing a first MQW, growing a tunnel junction layer, growing a second MQW, and growing an AlGaN / GaN superlattice layer; The specific steps for growing the first MQWs are: First, a first InGaN well layer is grown, followed by a first GaN barrier layer with a thickness of D1. Eight to 13 cycles of the first InGaN well layer and the first GaN barrier layer are repeated, and the In content in the first InGaN well layer is controlled to be 15-20% (the In content of 15-20% refers to the ratio of the number of In atoms to the total number of In / Ga / N atoms). The first MQWs emit blue light. The growth tunnel junction layer is specifically: First, a Si-doped InGaN layer is grown, and then a Si-doped GaN layer is grown. The sum of the thicknesses of the InGaN layer and the GaN layer is D2, and D2 is between 0.3 and 0.5 times that of D1. The specific steps for growing the second MQWs are: First, a second InGaN well layer is grown, and then a second GaN barrier layer with a thickness of D1 is grown. The second InGaN well layer and the second GaN barrier layer are grown repeatedly for 3-6 cycles. The In content in the second InGaN well layer is controlled to be 15-20% (the In content of 15-20% refers to the ratio of the number of In atoms to the total number of the three types of In / Ga / N atoms). The In content in the second InGaN well layer is controlled to gradually increase from the first cycle to the last cycle. The second MQWs emit green light. The specific steps for growing the AlGaN / GaN superlattice layer are as follows: The AlGaN / GaN superlattice layer is grown by a pulsed growth method. During the growth process, NH3 and TMAl are both pulsed. The Al composition gradient in AlGaN is controlled by controlling the TMAl introduction time t.

[0023] Further: The first GaN barrier layer and the second GaN barrier layer are doped with Si at the same time, and the Si doping concentration is 2E17-5E17.

[0024] The value of D1 is 8-15 nm.

[0025] The Si doping concentration in the tunnel junction layer is 2E17-5E17.

[0026] The In content gradually increases when growing the second MQWs, specifically: The molar content of In atoms in the second InGaN well layer increases gradually from the first period to the last period at a ratio of 0.5% to 1.5%.

[0027] When growing the AlGaN / GaN superlattice layer, NH3 and TMAl are both pulsed, specifically: The introduction and closing time of NH3 are both 1-2 seconds, the closing time of TMA1 is 1-4 seconds, and the pulse cycle is 50-100.

[0028] The Al composition gradient in AlGaN is controlled by controlling the introduction time t of TMAl, specifically: The TMAl introduction time t was controlled to decrease uniformly from 12 seconds to 2 seconds, so that the Al atomic molar content of the AlGaN layer was uniformly and gradually decreased from 20% to 6%.

[0029] In an embodiment of the present invention, a first MQW that can excite blue light is first grown, and then a second MQW that can excite green light is grown. Since the barrier of the green light well is significantly lower than that of the blue light well, and the hole mobility is only 1 / 10 of that of electrons, holes are easily confined in the green light well. The present invention enhances hole tunneling by introducing a tunnel junction layer between the first MQWs and the second MQWs. The thickness of the tunnel junction layer is controlled to be between 0.3 and 0.5 times the thickness of the first GaN barrier layer and the second GaN barrier layer. Firstly, the width of the barrier can be reduced, making it easier for holes to tunnel from the green light well to the blue light well. Secondly, the hole tunneling time can be made equivalent to the carrier lifetime, thereby increasing the hole concentration in the blue light well, so that there is sufficient carrier recombination in both the first MQWs and the second MQWs. At the same time, doping Si in the tunnel junction layer can increase carrier mobility, thereby improving radiative recombination efficiency and luminous efficiency. The thin tunnel junction layer may induce coupling between quantum wells, leading to broadening of the luminescence peak. This application introduces an AlGaN / GaN superlattice layer into the multi-quantum well and controls the gradual change of the Al component in the AlGaN by controlling the introduction time of TMAl to suppress wave function overlap and reduce coupling between quantum wells, thereby avoiding broadening of the luminescence peak and ensuring that the quantum well emits blue and green light at the same time. It can also improve the color saturation of the light and reduce the color temperature. The color saturation of the light can reach 98%, and the color temperature of the light can be as low as 2000K after chip packaging. When growing the second MQWs, controlling the In content in the InGaN well layer to gradually increase can reduce the built-in electric field, pre-compensate lattice stress, relieve compressive strain, and effectively solve the band tilt problem caused by the piezoelectric polarization field, thereby improving the radiative recombination efficiency and the luminous efficiency of the LED; compared with the existing technology, the present invention enhances the tunneling of holes by introducing a tunnel junction layer inside the multi-quantum well layer, and at the same time introduces an AlGaN / GaN superlattice layer. By controlling the introduction time of TMAl, the Al component in AlGaN is controlled to gradually change, thereby solving the problem of luminescence peak broadening, ensuring that the quantum well emits blue and green light at the same time, and improving the color saturation of the light and reducing the color temperature.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A blue-green dual-peak LED epitaxial growth method, characterized in that: The method comprises the following steps: Processing substrate, growing low-temperature GaN buffer layer, growing undoped GaN layer, growing Si-doped N-type GaN layer, growing multi-quantum well layer, growing AlGaN electron barrier layer, growing Mg-doped P-type GaN layer and cooling; The growing of the multi-quantum well layer comprises: The first MQWs are grown, a tunnel junction layer is grown, a second MQWs is grown, and an AlGaN / GaN superlattice layer is grown.

2. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 1, wherein: The first MQWs are grown as follows: First, a first InGaN well layer is grown, and then a first GaN barrier layer with a thickness of D1 is grown, and the growth of the first InGaN well layer and the first GaN barrier layer is repeated for 8 to 13 cycles; The In content in the first InGaN well layer is controlled to be 15-20%, and the first MQWs emit blue light.

3. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 1, wherein: The growth tunnel junction layer is specifically: First, a Si-doped InGaN layer is grown, and then a Si-doped GaN layer is grown, and the sum of the thicknesses of the InGaN layer and the GaN layer is D2, and D2 is 0.3-0.5 times that of D1.

4. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 2, wherein: The growth of the second MQWs is specifically as follows: First, a second InGaN well layer is grown, and then a second GaN barrier layer with a thickness of D1 is grown, and the growth of the second InGaN well layer and the second GaN barrier layer is repeated for 3-6 cycles; The In content in the second InGaN well layer is controlled to be 15-20%, and the In content in the second InGaN well layer is controlled to gradually increase from the first period to the last period, and the second MQWs emit green light.

5. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 4, characterized in that: The first GaN barrier layer and the second GaN barrier layer are both doped with Si, and the Si doping concentration is 2E17-5E17.

6. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 1, wherein: The AlGaN / GaN superlattice layer is grown using a pulse growth method; During the growth process, NH3 and TMAl are both introduced in pulses, and the Al composition gradient in AlGaN is controlled by controlling the introduction time t of TMAl.

7. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 6, wherein: The NH3 on and off time is 1-2 seconds, the TMA1 off time is 1-4 seconds, and the pulse cycle is 50-100; The TMAl introduction time t was controlled to decrease uniformly from 12 seconds to 2 seconds, so that the Al atomic molar content of the AlGaN layer was uniformly and gradually decreased from 20% to 6%.

8. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 2, wherein: The value of D1 is 8-15 nm.

9. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 3, wherein: The Si doping concentration in the tunnel junction layer is 2E17-5E17.

10. The method for growing a blue-green dual-peak epitaxial quantum well layer according to claim 4, characterized in that: The In content gradually increases when growing the second MQWs, specifically: The molar content of In atoms in the second InGaN well layer increases gradually from the first period to the last period at a ratio of 0.5% to 1.5%.