Single-chip multi-PN-junction RGB full-color LED

Abstract

The invention discloses a single-chip multi-PN junction RGB full-color LED which comprises a substrate, a first blue light emitting unit, a second green light emitting unit and a third red light emitting unit, the first blue light emitting unit, the second green light emitting unit and the third red light emitting unit are formed on the substrate through one-time epitaxy, and a first barrier layer and a first tunnel layer are sequentially arranged between the first blue light emitting unit and the second green light emitting unit in the growth direction. A second barrier layer and a second tunnel layer are sequentially arranged between the second green light emitting unit and the third red light emitting unit along the growth direction, and the first barrier layer and the second barrier layer are made of InyGa1-yN. The first barrier layer and the second barrier layer block the diffusion of Mg atoms to the tunnel layer, thereby reducing the impurity compensation effect of the PN junctions, and improving the tunneling efficiency between the PN junctions.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor materials, and in particular to a monolithic multi-PN junction RGB full-color LED. Background Art

[0002] In the field of semiconductor lighting and display, blue light, green light and red light are the three basic colors for full-color micro-display. However, traditional full-color micro-displays usually combine separate red, green and blue (RGB) light sources or pixels. This full-color technology is complex to manufacture, has high production costs, and has poor display effects, which seriously affects the widespread use of full-color micro-displays.

[0003] In order to overcome the above shortcomings, a new type of single-chip full-color LED is urgently needed to improve the display effect. Compared with traditional full-color technology, single-chip full-color LED technology has three obvious advantages: (1) The red, green and blue LED epitaxial layers are concentrated on the same substrate, thus avoiding the complex process of separately manufacturing the red, green and blue chip combination process in the traditional process; (2) Single-chip full-color LED technology can achieve higher integration, so more pixels can be arranged in a smaller space, thereby improving resolution and pixels; (3) Single-chip full-color LED technology can achieve better color performance and contrast. Since the red, green and blue LED epitaxial layers are directly integrated on the same substrate, the luminous intensity and luminous efficiency of each color can be more accurately controlled, thereby obtaining a more realistic and bright color display effect. In addition, this technology can also reduce crosstalk between colors and improve image clarity and contrast.

[0004] In order to realize the luminescence of a single RGB full-color LED, multiple PN junctions are used to connect three-color light-emitting units in series, and tunneling is required between the PN junctions to realize the transmission of current. One solution in the prior art is to set a tunnel layer between the light-emitting units, and the tunnel layer is N-type, and a PN junction is formed through the P-type layer of the light-emitting unit and the tunnel layer. However, the tunnel layer is grown after the P-type layer of the light-emitting unit, and Mg is doped in the P-type layer. The growth temperature of the tunnel layer is relatively high, and it is easy for Mg atoms in the P-type layer to diffuse into the adjacent tunnel layer, resulting in an impurity compensation effect at the PN junction, and the PN junction tunneling cannot be realized. Summary of the invention

[0005] The purpose of the present invention is to provide a monolithic multi-PN junction RGB full-color LED in view of the deficiencies in the prior art, by setting a barrier layer to block the diffusion of Mg atoms in the P-type layer of the light-emitting unit to the tunnel layer, thereby avoiding PN junction failure.

[0006] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a monolithic multi-PN junction RGB full-color LED, comprising: a substrate, and a blue light first light-emitting unit, a green light second light-emitting unit and a red light third light-emitting unit formed on the substrate by one-time epitaxy; a first barrier layer and a first tunnel layer are sequentially arranged between the blue light first light-emitting unit and the green light second light-emitting unit along the growth direction, and a second barrier layer and a second tunnel layer are sequentially arranged between the green light second light-emitting unit and the red light third light-emitting unit along the growth direction, wherein: the material of the first barrier layer and the second barrier layer is In y Ga 1-y N.

[0007] Optionally, the thickness of the first barrier layer and the second barrier layer is h, and h ranges from 10 nm to 50 nm.

[0008] Optionally, the In composition y in the first barrier layer and the second barrier layer is in the range of 0-0.1.

[0009] Optionally, the growth temperature of the first barrier layer and the second barrier layer is T, and the range of T is 850 degrees to 1000 degrees.

[0010] Optionally, the growth rate of the first barrier layer and the second barrier layer is V, and V ranges from 0.1Å / s to 1Å / s.

[0011] Optionally, the specific structure of the first blue light emitting unit, the second green light emitting unit and the third red light emitting unit is an N-type GaN layer, a multi-quantum well layer, a P-type Al a Ga 1-a N layer, P-type GaN layer and heavily doped P-type GaN layer.

[0012] Optionally, the first tunnel layer and the second tunnel layer are GaN containing Si, and the growth temperature of the first tunnel layer and the second tunnel layer is the same as the growth temperature of the first barrier layer and the second barrier layer.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The monolithic multi-PN junction RGB full-color LED provided by the present invention has a material of In grown between the first blue light emitting unit and the first tunnel layer and between the second green light emitting unit and the second tunnel layer. y Ga 1-y The first and second barrier layers of N are made of In y Ga 1-y Various defects and dislocations formed during the growth of the N barrier layer provide additional sites, making it easier for Mg to be replaced and embedded in In. y Ga 1-y The lattice of the N barrier layer blocks the diffusion of Mg atoms into the tunnel layer, reduces the impurity compensation effect of the PN junction, and improves the tunneling probability of the PN junction. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a monolithic multi-PN junction RGB full-color LED provided in an embodiment of the present invention.

[0015] Figure 2 A schematic structural diagram of a blue light first light emitting unit provided in an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram of the structure of a green light second light emitting unit provided in an embodiment of the present invention.

[0017] Figure 4 This is a schematic structural diagram of a red light third light emitting unit provided in an embodiment of the present invention.

[0018] Figure 5 This is a photoluminescence image of a single chip multi-PN junction RGB full-color LED in the present invention.

[0019] In the figure: 10 substrate, 20 buffer layer, 30 blue light first light emitting unit, 40 first barrier layer, 50 first tunnel layer; 60 green light second light emitting unit, 70 second barrier layer, 80 second tunnel layer, 90 red light third light emitting unit; 31 first N-type GaN layer, 32 blue light well preparation layer, 33 blue light multi-quantum well layer, 331 blue light quantum well, 332 blue light quantum barrier, 34 first P-type Al a Ga 1-a N layer, 35 a first P-type GaN layer, 36 a first heavily doped P-type GaN layer; 61 second N-type GaN layer, 62 green light well preparation layer, 63 green light multi-quantum well layer, 631 green light quantum well, 632 green light quantum barrier, 64 second P-type Al a Ga 1-a N layer, 65 a second P-type GaN layer, 66 a second heavily doped P-type GaN layer; 91 third N-type GaN layer, 92 red light well preparation layer, 93 red light multi-quantum well layer, 931 green light quantum well, 932 green light quantum barrier, 94 third P-type Al a Ga 1-a N layer, 95 a third P-type GaN layer, and 96 a third heavily doped P-type GaN layer. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the specific implementation methods or the prior art are clearly and completely described below, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the present invention, rather than all the embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present application provides a monolithic multi-PN junction RGB full-color LED, including: a substrate 10, and a blue light first light emitting unit 30, a green light second light emitting unit 60, and a red light third light emitting unit 90 formed on the substrate 10 by one-time epitaxy, a first barrier layer 40 and a first tunnel layer 50 are sequentially arranged between the blue light first light emitting unit 30 and the green light second light emitting unit 60 along the growth direction, and a second barrier layer 70 and a second tunnel layer 80 are sequentially arranged between the green light second light emitting unit 60 and the red light third light emitting unit 90 along the growth direction, wherein: the material of the first barrier layer 40 and the second barrier layer 70 is In y Ga 1-y N.

[0022] It should be noted that the present invention grows In between the light-emitting unit and the tunnel layer. y Ga 1-y N barrier layer, In y Ga 1-y Various defects and dislocations will be formed in the N barrier layer during the growth process. These defects can provide additional sites, making it easier for Mg to be replaced and embedded in the lattice, blocking the diffusion of Mg atoms to the tunnel layer, reducing the possibility of PN junction failure and increasing the tunneling probability of the PN junction.

[0023] In some embodiments of the present application, a buffer layer 20 is further grown between the substrate 10 and the first blue light emitting unit 30 .

[0024] In some embodiments of the present application, the thickness of the first barrier layer 40 and the second barrier layer 70 is h, and the range of h is 10 nm-50 nm. y Ga 1-y If the thickness of the N barrier layer is too thick, there will be more defects, which may easily lead to poor crystal quality of the underlying layer.

[0025] In some embodiments of the present application, the In composition y in the first barrier layer 40 and the second barrier layer 70 is in the range of 0-0.1.

[0026] In some embodiments of the present application, the growth temperature of the first barrier layer 40 and the second barrier layer 70 is T, and the range of T is 850 degrees to 1000 degrees.

[0027] In some embodiments of the present application, the growth rate of the first barrier layer 40 and the second barrier layer 70 is V, and the range of V is 0.1Å / s-1Å / s.

[0028] It should be noted that In y Ga 1-y N material is an important semiconductor material. During its epitaxial growth process, precise control of temperature, rate, composition and thickness parameters is crucial to obtain high-quality In y Ga 1-y The N barrier layer and its barrier effect are crucial. y Ga 1-y In order to obtain high-quality In with a certain In composition range, y Ga 1-y The N barrier layer must first be controlled within a certain growth temperature range. Too fast a growth rate will easily produce new defects, affecting the crystal quality of the underlying tunnel layer. y Ga 1-y The thickness of the N barrier layer is too thin to block the diffusion of Mg, while the In y Ga 1-y If the N barrier layer is too thick, the tunnel distance between the PN junctions will increase, which will increase the difficulty of tunneling. y Ga 1-y The N barrier layer requires a suitable range of growth conditions to be controlled.

[0029] In some embodiments of the present application, the specific structures of the blue light first light emitting unit 30, the green light second light emitting unit 60 and the red light third light emitting unit 90 are sequentially stacked N-type GaN layer, multi-quantum well layer, P-type Al a Ga 1-a N layer, P-type GaN layer and heavily doped P-type GaN layer.

[0030] In some embodiments of the present application, a preparation layer is further grown between the N-type GaN layer and the multi-quantum well layer.

[0031] In some embodiments of the present application, the first tunnel layer 50 and the second tunnel layer 80 are GaN containing Si, and the growth temperature of the first tunnel layer 50 and the second tunnel layer 80 is the same as the growth temperature of the first barrier layer 40 and the second barrier layer 70 . Example 1

[0032] See also Figure 1The present invention discloses a monolithic multi-PN junction RGB full-color LED, which includes, from bottom to top, a substrate 10, a buffer layer 20, a blue light first light emitting unit 30, a green light second light emitting unit 60, and a red light third light emitting unit 90. A first barrier layer 40 and a first tunnel layer 50 are grown between the blue light first light emitting unit 30 and the green light second light emitting unit 60, and a second barrier layer 70 and a second tunnel layer 80 are grown between the green light second light emitting unit 60 and the red light third light emitting unit 90. The substrate 10 is a silicon substrate, and the materials of the first barrier layer 40 and the second barrier layer 70 are In y Ga 1-y N, wherein the In component is 0.07, and the thickness of the first barrier layer 40 and the second barrier layer 70 is 10 nm. The first tunnel layer 50 and the second tunnel layer 80 are Si-doped GaN layers, wherein the Si doping concentration is 1E20 atom / cm 3 .

[0033] See also Figure 2 The first blue light emitting unit 30 includes a first N-type GaN layer 31, a blue light well preparation layer 32, a blue light multi-quantum well layer 33, and a first P-type Al a Ga 1-a N layer 34, a first P-type GaN layer 35 and a first heavily doped P-type GaN layer 36. a Ga 1-a The doping elements of the N layer 34, the first P-type GaN layer 35 and the first heavily doped P-type GaN layer 36 are all Mg, and the first P-type Al a Ga 1-a The thickness of the N layer 34 (a=0.2) is 30nm, and the Mg doping concentration is 3E19atom / cm 3 ; The Mg doping concentration of the first P-type GaN layer 35 is 1E20atom / cm 3 The Mg doping concentration of the first heavily doped P-type GaN layer 36 is 1.5E20atom / cm 3 .

[0034] The blue light multi-quantum well layer 33 is composed of blue light quantum wells 331 and blue light quantum barriers 332 which are periodically stacked alternately, and the number of periods is 6. The blue light quantum well layer 331 is In x Ga 1-x The N layer (x=0.18) has a thickness of 2.5 nm, and the blue light quantum barrier 322 is GaN, with a thickness of 10 nm.

[0035] See also Figure 3 The green light second light emitting unit 60 includes a second N-type GaN layer 61, a green light well preparation layer 62, a green light multi-quantum well layer 63, and a second P-type Al a Ga1-a N layer 64, a second P-type GaN layer 65 and a second heavily doped P-type GaN layer 66. a Ga 1-a The doping elements of the N layer 64, the second P-type GaN layer 65 and the second heavily doped P-type GaN layer 66 are all Mg. a Ga 1-a The thickness of the N layer 64 (a=0.2) is 30 nm, and the Mg doping concentration is 3E19 atom / cm 3 The Mg doping concentration of the second P-type GaN layer 65 is 1E20atom / cm 3 The Mg doping concentration of the second heavily doped P-type GaN layer 66 is 1.5E20atom / cm 3 .

[0036] The green multi-quantum well layer 63 is composed of green quantum wells 631 and green quantum barriers 632 that are periodically stacked alternately, and the number of cycles is 3. The green quantum well 631 is In x Ga 1-x The N layer (x=0.28) has a thickness of 2.8 nm, and the green light quantum barrier 632 is GaN, with a thickness of 10 nm.

[0037] See also Figure 4 The third red light emitting unit 90 includes a third N-type GaN layer 91, a red light well preparation layer 92, a red light multi-quantum well layer 93, and a third P-type Al a Ga 1-a N layer 94, a third P-type GaN layer 95 and a third heavily doped P-type GaN layer 96. a Ga 1-a The doping elements of the N layer 94, the third P-type GaN layer 95 and the third heavily doped P-type GaN layer 96 are all Mg. a Ga 1-a The thickness of the N layer 94 (a=0.2) is 30 nm, and the Mg doping concentration is 3E19 atom / cm 3 The Mg doping concentration of the third P-type GaN layer 95 is 1E20atom / cm 3 The Mg doping concentration of the third heavily doped P-type GaN layer 96 is 1.5E20atom / cm 3 .

[0038] The red light multi-quantum well layer 93 is composed of periodically alternately stacked red light quantum wells 931 and red light quantum barriers 932, and the number of periods is 3. The red light quantum well 931 is In x Ga 1-xThe N layer (x=0.35) has a thickness of 3.5 nm, and the red light quantum barrier 932 is GaN, with a thickness of 10 nm.

[0039] See also Figure 5 This is the photoluminescence image of the monolithic multi-PN junction RGB full-color LED of sample 1 prepared in this embodiment.

[0040] In this embodiment, the growth methods of the first barrier layer 40 and the second barrier layer 70 are the same. The first barrier layer 40 and the growth steps before the first barrier layer 40 in this embodiment are described below, including the following steps: Step (1), growing the buffer layer 20: placing the Si (111) substrate in a MOCVD reaction chamber, introducing a TMAl source, NH3 and H2 at a temperature of 1200°C, and growing the buffer layer to a thickness of 2800Å.

[0041] Step (2), growing the first blue light emitting unit 30: (a) first turn off the TMAl source, grow the first N-type GaN layer 31, introduce TMG source, NH3 and H2 at a temperature of 1120 degrees, and dope Si with a concentration of 2E18atom / cm 3 , the growth thickness is 2.5um. (b) Cool down and grow the blue light well preparation layer 32, turn off the TMG source and H2, turn on the TMIn source and TEG source, and pass N2, and the growth thickness is 1500 Å. (c) Grow the blue light multi-quantum well layer 33, and periodically grow 6 InGaN / GaN (2.5nm / 10nm) quantum wells. (d) Then turn off the TMIn source, pass Cp2Mg, TMG source and NH3 and raise the temperature to 1000 degrees to grow the first P-type Al a Ga 1-a N layer 34 , a first P-type GaN layer 35 and a first heavily doped P-type GaN layer 36 .

[0042] Step (3), growing the first barrier layer 40: turning off the CP2Mg source and the TMG source, turning on the TMIn source and the TEG source, cooling to 950°C while introducing ammonia to grow the first barrier layer 40, with an In component y of 7%, a growth rate of 0.4 Å / s, and a growth thickness of 100 Å.

[0043] Step (4), growing the first tunnel layer 50: turn off the TMIn source, introduce SiH4 at the same temperature, and dope the Si to a concentration of 1E20atom / cm 3 . Example 2

[0044] The substrate in Example 2 is different from that in Example 1, and the substrate in Example 2 is a patterned sapphire substrate. The growth methods of the first barrier layer 40 and the second barrier layer 70 are the same, and the blue light multi-quantum well layer 33, the green light multi-quantum well layer 63 and the red light multi-quantum well layer 93 are the same as those in Example 1. The following describes the first barrier layer and the first barrier layer front growth step, which includes the following steps: Step (1), growing the buffer layer 20: placing the sapphire substrate in a MOCVD reaction chamber, introducing TMAl source, NH3 and H2, and TMG source at a temperature of 920°C to grow AlGaN.

[0045] Step (2), growing the first blue light emitting unit 30: (a) first turn off the TMAl source, grow the first N-type GaN layer 31, introduce TMG source, NH3 and H2 at a temperature of 1120 degrees, and dope Si with a concentration of 5E18atom / cm 3 , the growth thickness is 5um. (b) Cool down and grow the blue light well preparation layer 32, turn off the TMG source and H2, turn on the TMIn source and TEG source, and pass N2, and the growth thickness is 1500 Å. (c) Blue light multi-quantum well layer 33, periodically grow 6 InGaN / GaN (2.5nm / 10nm) quantum wells. (d) Then turn off the TMIn source, pass Cp2Mg, TMG source and NH3 to grow to 1000 degrees to grow the first P-type Al a Ga 1-a N layer 34 , a first P-type GaN layer 35 and a first heavily doped P-type GaN layer 36 .

[0046] Step (3), growing the first barrier layer 40: turn off the CP2Mg source and the TMG source, turn on the TMIn source and the TEG source, cool down to 950 degrees while introducing ammonia to grow InGaN, with an In component of 7%, a growth rate of 0.4Å / s, and a growth thickness of 500Å.

[0047] Step (4), growing the first tunnel layer 50: turn off the TMIn source, introduce SiH4 at the same temperature, and the Si doping concentration reaches 2E19atom / cm 3 .

Claims

1. A monolithic multi-PN junction RGB full-color LED, comprising: A substrate, and a blue light first light emitting unit, a green light second light emitting unit and a red light third light emitting unit formed on the substrate by one-time epitaxy, characterized in that a first barrier layer and a first tunnel layer are sequentially arranged between the blue light first light emitting unit and the green light second light emitting unit along the growth direction, and a second barrier layer and a second tunnel layer are sequentially arranged between the green light second light emitting unit and the red light third light emitting unit along the growth direction, wherein: the material of the first barrier layer and the second barrier layer is In y Ga 1-y N.

2. The monolithic multi-PN junction RGB full-color LED according to claim 1, characterized in that: The thickness of the first barrier layer and the second barrier layer is h, and the range of h is 10nm-50nm.

3. The monolithic multi-PN junction RGB full-color LED as claimed in claim 1, characterized in that: The In composition y in the first barrier layer and the second barrier layer is in the range of 0-0.

1.

4. The monolithic multi-PN junction RGB full-color LED as claimed in claim 3, characterized in that: The growth temperature of the first barrier layer and the second barrier layer is T, and the range of T is 850 degrees to 1000 degrees.

5. The monolithic multi-PN junction RGB full-color LED as claimed in claim 3, characterized in that: The growth rates of the first barrier layer and the second barrier layer are V, and the range of V is 0.1Å / s-1Å / s.

6. The monolithic multi-PN junction RGB full-color LED according to claim 1, characterized in that: The specific structure of the blue light first light emitting unit, the green light second light emitting unit and the red light third light emitting unit is a sequentially stacked N-type GaN layer, a multi-quantum well layer, a P-type Al a Ga 1-a N layer, P-type GaN layer and heavily doped P-type GaN layer.

7. The monolithic multi-PN junction RGB full-color LED as claimed in claim 1, characterized in that: The first tunnel layer and the second tunnel layer are GaN containing Si, and the growth temperature of the first tunnel layer and the second tunnel layer is the same as the growth temperature of the first barrier layer and the second barrier layer.

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