Double-junction infrared LED epitaxial structure and infrared LED chip

Abstract

The invention provides a double-junction infrared LED epitaxial structure and an infrared LED chip, light absorption layers (a first light absorption layer and a second light absorption layer) are arranged on the surfaces of the two sides of the double-junction infrared LED epitaxial structure, and each light absorption layer comprises an AlGaAs / GaAs heterostructure, so that the band gap energy of each light absorption layer is slightly lower than the photon energy emitted by active regions of two junctions; on the basis, useless infrared photons emitted from the active region and propagated to the two sides of the device can be effectively absorbed by the two light absorption layers; specifically, for visible red light (620-750 nm), the photon energy of the visible red light is higher than the band gap of AlGaAs, and the visible red light can be strongly absorbed by the layer and cannot escape to the outside of the device, so that red exposure is eliminated. Secondly, through the tunnel junction technology, the two light-emitting epitaxial structures (the first epitaxial structure and the second epitaxial structure) are connected in series, and the secondary utilization of current carriers is realized in the process, so that the internal quantum efficiency (IQE) and the power conversion efficiency are remarkably improved under the same driving current, the total light output power (brightness) of the device is improved, and the light-emitting efficiency of the device is improved. Therefore, the problem of brightness loss caused by the first light absorption layer and the second light absorption layer is well compensated, and gain is finally realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LED chip, and particularly relates to a double-junction infrared LED epitaxial structure and an infrared LED chip. BACKGROUND

[0002] The infrared LED is a kind of diode capable of emitting infrared rays, and the wavelength mainly concentrates on 0.7-1.2 μm. It is a kind of light-emitting device capable of converting electric energy into light energy, and has the advantages of small size, low power consumption, good directivity and the like, and is widely applied to the fields of safety monitoring, wearable devices, infrared communication, infrared remote control devices, light sources for sensors and night lighting and the like. Since the light-emitting range of the 940 nm infrared LED covers a wide range (0.7-1.2 μm), the light in the 0.7-0.8 μm band is visible to the naked eye, and this part of the weak red light source is called red exposure. The red exposure does not have the concealment and confidentiality for the infrared LED of the security monitoring camera.

[0003] However, for the infrared LED with a center wavelength of 940 nm, the light emission is not ideal monochromatic light, but there is an emission spectrum with a certain width (the half-height width FWHM is usually 30-50 nm). This means that the light emitted not only contains the target 940 nm infrared light, but also inevitably covers a part of the light with a shorter wavelength (higher energy), and the spectral range can cover about 700 nm to 1200 nm.

[0004] The problem is that the visual cells of the human eye still have certain perception ability for near-infrared light with a wavelength in the range of 700 nm to 800 nm (although the sensitivity is much lower than that of visible light). Therefore, when a high-power 940 nm LED is working, the “short-wave leakage” of the 700-800 nm band in its spectrum will be perceived by the human eye as a circle of dim, visible reddish-brown or dark red halo, which is called “red glow”. In the application scenarios of security monitoring and the like which emphasize concealment, the red glow problem brings fatal defects:

[0005] Loss of concealment: obvious red exposure will directly expose the position of the camera, making the monitoring intention invalid, and criminals can easily evade or damage the equipment.

[0006] Lack of confidentiality: in occasions where secret defense is required, red exposure will remind people that they are in a monitored state, losing the suddenness and confidentiality of monitoring.

[0007] Poor user experience: when used for sensor of consumer electronic products (such as distance sensor of TV), the continuous red halo will also affect the appearance aesthetics of the equipment, and even cause interference to the user in a dark environment.

[0008] In view of this, the present inventors specially design a double-junction infrared LED epitaxial structure and infrared LED chip, and the present case is generated accordingly. SUMMARY

[0009] The present application aims to provide a double-junction infrared LED epitaxial structure and infrared LED chip, effectively solving the red exposure technical problems existing in the prior art infrared LED chip technology, and improving the light emitting efficiency and luminous brightness of the infrared LED.

[0010] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0011] A double-junction infrared LED epitaxial structure, comprising:

[0012] a substrate;

[0013] a first epitaxial structure, a tunnel junction, a second epitaxial structure and a window layer stacked in the first direction in turn, the first direction being perpendicular to the substrate and pointing from the substrate to the first epitaxial structure;

[0014] a light absorption layer, the light absorption layer being arranged on a side surface of the first epitaxial structure close to the substrate, or the light absorption layer being arranged on a side surface of the second epitaxial structure close to the window layer; the light absorption layer comprising an AlGaAs / GaAs heterostructure.

[0015] Preferably, a first light absorption layer is arranged on a side surface of the first epitaxial structure close to the substrate, and a second light absorption layer is arranged on a side surface of the second epitaxial structure close to the window layer; the first light absorption layer comprising an AlGaAs / GaAs heterostructure, and the second light absorption layer comprising an AlGaAs / GaAs heterostructure.

[0016] Preferably, the first light absorption layer comprises a GaAs layer and an AlGaAs layer stacked in the first direction in turn.

[0017] Preferably, the second light absorption layer comprises an AlGaAs layer and a GaAs layer stacked in the first direction in turn.

[0018] Preferably, in the first light absorption layer, the band gap of the AlGaAs layer gradually changes. Optionally, the AlGaAs layer comprises AlGaAs with gradually changing aluminum composition. x Ga 1-x As, 0.01 < x < 0.1, x gradually increasing along the first direction.

[0019] Preferably, in the first light absorption layer, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

[0020] Preferably, in the first light-absorbing layer, the thickness of the AlGaAs layer is between 1 μm and 3 μm, inclusive; and the thickness of the GaAs layer is between 0.5 μm and 2 μm, inclusive.

[0021] Preferably, in the second light-absorbing layer, the band gap of the AlGaAs layer is graded. Optionally, the AlGaAs layer comprises an Al y Ga 1-y As layer, 0.01 < y < 0.1, y gradually decreases along the first direction.

[0022] Preferably, in the second light-absorbing layer, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

[0023] Preferably, in the second light-absorbing layer, the thickness of the AlGaAs layer is between 1 μm and 3 μm, inclusive; and the thickness of the GaAs layer is between 0.5 μm and 2 μm, inclusive.

[0024] Preferably, an N-type ohmic contact layer is provided between the substrate and the first light-absorbing layer.

[0025] Preferably, the first epitaxial structure comprises, in order along the first direction, a first N-type confinement layer, a first active region, and a first P-type confinement layer.

[0026] The second epitaxial structure comprises, in order along the first direction, a second N-type confinement layer, a second active region, and a second P-type confinement layer.

[0027] The tunnel junction comprises, in order along the first direction, a heavily doped N-type layer and a heavily doped P-type layer.

[0028] The present application also provides an infrared LED chip, comprising:

[0029] The substrate of the double-junction infrared LED epitaxial structure of claim 10 is removed to expose the N-type ohmic contact layer.

[0030] A metal mirror is laminated to a side surface of the window layer facing away from the second epitaxial structure.

[0031] A bonding layer is provided to a side surface of the metal mirror facing away from the window layer.

[0032] A substrate is provided to a side surface of the bonding layer facing away from the metal mirror.

[0033] A P-type electrode is provided to a side surface of the substrate facing away from the bonding layer.

[0034] An N-type electrode is laminated to a side surface of the N-type ohmic contact layer facing away from the first light-absorbing layer.

[0035] According to the technical solution, the double-junction infrared LED epitaxial structure is provided by sequentially stacking a first epitaxial structure, a tunnel junction, a second epitaxial structure, and a window layer, the first direction is perpendicular to the substrate and is directed from the substrate to the first epitaxial structure; a first light-absorbing layer is arranged on a side surface of the first epitaxial structure close to the substrate, and a second light-absorbing layer is arranged on a side of the second epitaxial structure close to the window layer; the first light-absorbing layer comprises an AlGaAs / GaAs heterostructure, and the second light-absorbing layer comprises an AlGaAs / GaAs heterostructure. In the application, the light-absorbing layers (the first light-absorbing layer and the second light-absorbing layer) are arranged on the two side surfaces of the double-junction infrared LED epitaxial structure, and the light-absorbing layers comprise AlGaAs / GaAs heterostructures, so that the band gap energy is slightly lower than the photon energy emitted by the active regions of the two junctions; based on this, the “useless” infrared photons emitted from the active regions and propagating to the two sides of the device can be effectively absorbed by the two light-absorbing layers; specifically, for visible red light (620-750 nm), the photon energy is higher than the band gap of AlGaAs, and the red light is strongly absorbed by the layer and cannot escape to the outside of the device, thereby eliminating “red exposure”. At the same time, the first / second light-absorbing layer is located on the path of current injection, and the heterojunction interface formed by AlGaAs / GaAs can provide an additional potential barrier, effectively limiting the carriers (electrons and holes) in the respective active regions, preventing them from excessively diffusing to the non-light-emitting area and causing non-radiative recombination, and further ensuring high internal quantum efficiency. Secondly, the two light-emitting epitaxial structures (the first epitaxial structure and the second epitaxial structure) are connected in series through the tunnel junction technology, based on which, under the driving of an external voltage, the remaining electrons and holes that do not emit light in the first epitaxial structure will be injected into the second epitaxial structure through a very thin potential barrier layer by the tunnel effect with the help of the designed built-in electric field and the tunnel layer, and emit a second photon through secondary recombination. This process realizes the secondary use of carriers, which significantly improves the internal quantum efficiency (IQE) and the power conversion efficiency under the same driving current, so as to improve the total light output power (brightness) of the device, thereby well compensating for the brightness loss problem caused by the first and second light-absorbing layers, and finally realizing gain.

[0036] Further, by setting the first light-absorbing layer includes GaAs layer and AlGaAs layer stacked in the first direction, the wide band gap material (AlGaAs layer) is used as the first line of defense, and the highest energy photons are preferentially absorbed near the active region of the first epitaxial structure to reduce the non-radiative recombination probability of the highest energy photons, thereby solving the problem of affecting the reliability of the device due to local heating caused by the highest energy photons.

[0037] Similarly, by setting the second light-absorbing layer includes AlGaAs layer and GaAs layer stacked in the first direction, the wide band gap material (AlGaAs layer) is used as the first line of defense, and the highest energy photons are preferentially absorbed near the active region of the second epitaxial structure to reduce the non-radiative recombination probability of the highest energy photons, thereby solving the problem of affecting the reliability of the device due to local heating caused by the highest energy photons; the narrow band gap material (GaAs) is used as the second line of defense for fine filtering, so that the lowest energy target infrared photons (such as 940nm wavelength photons) can successively pass through the AlGaAs and GaAs layers and be emitted from the chip.

[0038] Then, by setting the band gap of the AlGaAs layer in the first light-absorbing layer gradually changes, and optionally, the AlGaAs layer includes Al x Ga 1-x As, 0.01 < x < 0.1, x gradually increases along the first direction, or the band gap of the AlGaAs layer in the second light-absorbing layer gradually changes. Optionally, the AlGaAs layer includes an Al

[0039] The application also provides an infrared LED chip based on the above-mentioned double-junction infrared LED epitaxial structure, which has the above-mentioned beneficial effects. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0041] Figure 1Structure diagram of a double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0042] Figure 2 Structure diagram of a first light-absorbing layer of a double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0043] Figure 3 Structure diagram of a tunnel junction of another double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0044] Figure 4 Structure diagram of a second light-absorbing layer of a double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0045] Figure 5 Structure diagram of a first active region of a double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0046] Figure 6 Structure diagram of a second active region of a double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0047] Figure 7 Structure diagram of still another double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0048] Figure 8 Structure diagram of another double-junction infrared LED epitaxial structure provided in Embodiment 1 of the present application;

[0049] Explanation of symbols in the figure:

[0050] 1, substrate;

[0051] 2, N-type buffer layer;

[0052] 3, N-type etching stop layer

[0053] 4, N-type ohmic contact layer

[0054] 5, first light-absorbing layer, 51, GaAs layer, 52, AlGaAs layer;

[0055] 6, first epitaxial structure, 61, first N-type confinement layer, 62, first active region, 63, first P-type confinement layer, 62.1, potential well material layer, 62.2, potential barrier material layer;

[0056] 7, tunnel junction, 71, heavily doped N-type AlGaAs layer, 72, heavily doped P-type GaAs layer;

[0057] 8. Second epitaxial structure, 81. Second N-type confinement layer, 82. Second active region, 83. Second P-type confinement layer, 82.1. Potential well material layer, 82.2. Potential barrier material layer;

[0058] 9. Second light absorption layer, 91. AlGaAs layer, 92. GaAs layer;

[0059] 10. P-type window layer. DETAILED DESCRIPTION

[0060] In order to make the content of the present application clearer, the content of the present application will be further described below in combination with the drawings. The present application is not limited to this specific embodiment. Based on the embodiment in the present application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0061] Embodiment 1

[0062] A double-junction infrared LED epitaxial structure comprises:

[0063] Substrate 1;

[0064] A first epitaxial structure 6, a tunnel junction 7, a second epitaxial structure 8 and a window layer are sequentially stacked along a first direction, the first direction being perpendicular to the substrate 1 and pointing from the substrate 1 to the first epitaxial structure 6;

[0065] A light absorption layer is arranged on a side surface of the first epitaxial structure 6 close to the substrate 1, or the light absorption layer is arranged on a side surface of the second epitaxial structure 8 close to the window layer; the light absorption layer comprises an AlGaAs / GaAs heterostructure.

[0066] Preferably, a first light absorption layer 5 is arranged on a side surface of the first epitaxial structure 6 close to the substrate 1, and a second light absorption layer 9 is arranged on a side surface of the second epitaxial structure 8 close to the window layer; the first light absorption layer 5 comprises an AlGaAs / GaAs heterostructure, and the second light absorption layer 9 comprises an AlGaAs / GaAs heterostructure.

[0067] It is worth mentioning that the type of substrate 1 is not limited in the semiconductor epitaxial structure of the present embodiment, for example, the substrate 1 can be but is not limited to a GaAs substrate 1, etc. In addition, the specific material type of the epitaxial structure can also be not limited in the infrared LED chip of the present embodiment, for example, the epitaxial structure can be but is not limited to an AlGaAs or AlGaAsP material system.

[0068] The first epitaxial structure 6 comprises a first N-type confinement layer 61, a first active region 62 and a first P-type confinement layer 63 stacked in sequence along the first direction; the second epitaxial structure 8 comprises a second N-type confinement layer 81, a second active region 82 and a second P-type confinement layer 83 stacked in sequence along the first direction; the tunnel junction 7 comprises a heavily doped N-type layer and a heavily doped P-type layer stacked in sequence along the first direction.

[0069] On the basis of the above-mentioned embodiments, in an embodiment of the present application, the first epitaxial structure 6 and the second epitaxial structure 8 comprise functional layers based on an AlGaAs material system, and the window layer comprises a P-type GaP window layer, the tunnel junction 7 comprises a heavily doped N-type AlGaAs layer 71 and a heavily doped P-type GaAs layer 72 stacked in sequence along the first direction, the doping concentration of the heavily doped N-type AlGaAs layer 71 is 1E19 cm -3 and above (specifically, the dopant is Si, and the doping concentration is 1E19-2E20 cm -3 , including the end value); the doping concentration of the heavily doped P-type GaAs layer 72 is 1E19 cm -3 and above (specifically, the dopant is Mg, and the doping concentration is 1E19-2E20 cm -3 , including the end value). Specifically, the first N-type confinement layer 61 comprises an N-type AlGaAs confinement layer, the first active region 62 comprises an InGaAs / AlGaAsP active region, and the first P-type confinement layer 63 comprises a P-type AlGaAs confinement layer; the second N-type confinement layer 81 comprises an N-type AlGaAs confinement layer, the second active region 82 comprises an InGaAs / AlGaAsP active region, and the second P-type confinement layer 83 comprises a P-type AlGaAs confinement layer.

[0070] Further, the thickness of InGaAs in the first / second active region 82 is 6-8 nm; the thickness of AlGaAsP in the first quantum well is 20-30 nm; and the number of InGaAs / AlGaAsP pairs is 4-12.

[0071] On the basis of the above-mentioned embodiments, in an embodiment of the present application, the first light-absorbing layer 5 comprises a GaAs layer 51 and an AlGaAs layer 52 stacked in sequence along the first direction.

[0072] On the basis of the above-mentioned embodiments, in an embodiment of the present application, the second light-absorbing layer 9 comprises an AlGaAs layer 91 and a GaAs layer 92 stacked in sequence along the first direction.

[0073] On the basis of the above-mentioned embodiments, in one embodiment of the present application, in the first light-absorbing layer 5, the band gap of the AlGaAs layer gradually changes. Optionally, the AlGaAs layer comprises an Al x Ga 1-x As layer, 0.01 < x ≤ 0.1, along the first direction, x gradually increases.

[0074] On the basis of the above-mentioned embodiments, in one embodiment of the present application, in the first light-absorbing layer 5, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

[0075] On the basis of the above-mentioned embodiments, in one embodiment of the present application, in the first light-absorbing layer 5, the thickness of the AlGaAs layer is between 1 μm and 3 μm, inclusive; the thickness of the GaAs layer is between 0.5 μm and 2 μm, inclusive.

[0076] On the basis of the above-mentioned embodiments, in one embodiment of the present application, in the second light-absorbing layer 9, the band gap of the AlGaAs layer gradually changes. Optionally, the AlGaAs layer comprises an Al y Ga 1-y As layer, 0.01 < y ≤ 0.1, along the first direction, y gradually decreases.

[0077] On the basis of the above-mentioned embodiments, in one embodiment of the present application, in the second light-absorbing layer 9, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

[0078] On the basis of the above-mentioned embodiments, in one embodiment of the present application, in the second light-absorbing layer 9, the thickness of the AlGaAs layer is between 1 μm and 3 μm, inclusive; the thickness of the GaAs layer is between 0.5 μm and 2 μm, inclusive.

[0079] On the basis of the above-mentioned embodiments, in one embodiment of the present application, an N-type ohmic contact layer 4 is arranged between the substrate 1 and the first light-absorbing layer 5.

[0080] On the basis of the above-mentioned embodiments, in one embodiment of the present application, an N-type buffer layer 2 and an N-type etching stop layer 3 are further arranged in sequence between the substrate 1 and the N-type ohmic contact layer 4.

[0081] The embodiment of the present application further provides a preparation method of the double-junction infrared LED epitaxial structure, and the preparation method comprises the following steps:

[0082] S01, providing a substrate 1;

[0083] Optionally, the substrate 1 is a GaAs substrate 1, but the present application is not limited thereto, and the specific substrate can be determined according to the actual situation.

[0084] S02, forming an N-type buffer layer 2 on the surface of the substrate 1;

[0085] Optionally, the N-type buffer layer 2 is an N-type GaAs buffer layer;

[0086] Specifically, the GaAs substrate 1 is placed in a reaction chamber by using the MOCVD technology, AsH3 source and TMGa source are introduced, GaAs material layer is grown at a temperature in the range of 600-800 ℃, the thickness is between 0.1-0.5 μm, and N-type doping source (which can be Si / Te source) is doped, and the carrier concentration is in the range of 7E17 / cm3-3E18 / cm 3 ; to obtain an N-type GaAs buffer layer.

[0087] S03, forming an N-type etching stop layer 3 on the surface of the N-type buffer layer 2;

[0088] Optionally, the N-type etching stop layer 3 is an N-type GaInP etching stop layer;

[0089] Specifically, the temperature is controlled in the range of 630-750 ℃, the AsH3 source is switched to the PH3 source, and the TMIn source is introduced, the GaInP material layer is grown, the thickness is between 0.03-0.3 μm, and the N-type doping source (which can be Si / Te source) is doped, and the carrier concentration is 6E17 / cm 3 -3E18 / cm 3 ; to obtain an N-type GaInP etching stop layer, as a stop protection layer for subsequent etching removal of the substrate 1 and the buffer layer.

[0090] S04, forming an N-type ohmic contact layer 4 on the surface of the N-type etching stop layer 3;

[0091] Optionally, the N-type ohmic contact layer 4 includes an N-type GaAs ohmic contact layer;

[0092] Specifically, the temperature is in the range of 600-800 ℃, the PH3 source is switched to the AsH3 source, the TMIn source is turned off, the GaAs material layer is grown, the thickness is between 0.03-0.2 μm, the N-type doping source (which can be Si / Te source) is doped, and the carrier concentration is 6E17 / cm 3 -4E18 / cm 3 ; to obtain an N-type GaAs ohmic contact layer.

[0093] S05, forming a first light-absorbing layer 5 on the surface of the N-type ohmic contact layer 4, the first light-absorbing layer 5 including an AlGaAs / GaAs heterostructure;

[0094] Optionally, the first light-absorbing layer 5 comprises a GaAs layer and an AlGaAs layer stacked in sequence along the first direction.

[0095] Based on the above-mentioned embodiments, in one embodiment of the present application, in the first light-absorbing layer 5, the band gap of the AlGaAs layer gradually changes. Optionally, the AlGaAs layer comprises Al x Ga 1-x As, 0.01 < x < 0.1, along the first direction, x gradually increases.

[0096] Based on the above-mentioned embodiments, in one embodiment of the present application, in the first light-absorbing layer 5, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

[0097] Based on the above-mentioned embodiments, in one embodiment of the present application, in the first light-absorbing layer 5, the thickness of the AlGaAs layer is between 1 μm and 3 μm, inclusive; and the thickness of the GaAs layer is between 0.5 μm and 2 μm, inclusive.

[0098] S06, forming a first N-type confinement layer 61 on the surface of the first light-absorbing layer 5;

[0099] Optionally, the first N-type confinement layer 61 comprises an N-type AlGaAs confinement layer.

[0100] Specifically, an AlGaAs material layer is grown, the component is adjusted so that the Al component is between 15% and 50%, the thickness is between 0.1 μm and 0.6 μm, and an N-type doping source (which can be a Si or Te source) is doped, with a carrier concentration of 4E17 / cm 3 -3E18 / cm 3 to obtain the N-type AlGaAs confinement layer.

[0101] S07, forming a first active region 62 on the surface of the first N-type confinement layer 61;

[0102] Optionally, the first active region 62 comprises an InGaAs / AlGaAsP active layer.

[0103] Specifically, the temperature is maintained at 600-800℃, and an InGaAs / AlGaAsP structure is grown by controlling TMAl source, TMIn source and PH3 source, wherein InGaAs is a potential well material layer 62.1, and AlGaAsP is a potential barrier material layer 62.2; 4-12 pairs of InGaAs / AlGaAsP structures are repeatedly grown without doping source, to obtain the first active region 62.

[0104] S08, forming a first P-type confinement layer 63 on the surface of the first active region 62;

[0105] Optionally, the first P-type confinement layer 63 comprises a P-type AlGaAs confinement layer.

[0106] Specifically, an AlGaAs material layer is grown, with an Al component between 15% and 50%, a thickness between 0.1 and 0.6 μm, and a P-type dopant source (which can be a Mg / C / Zn dopant source) incorporated therein, with a carrier concentration of 4E17 / cm 3 -1E18 / cm 3 ; to obtain a P-type AlGaAs confinement layer.

[0107] S09, forming a tunnel junction 7 on the surface of the first P-type confinement layer 63;

[0108] The tunnel junction 7 comprises a heavily doped N-type AlGaAs layer 71 and a heavily doped P-type GaAs layer 72 stacked in a first direction, the heavily doped N-type AlGaAs layer 71 having a doping concentration of 1E19 cm -3 and above (specifically, the dopant is Si, with a doping concentration of 1E19-2E20 cm -3 , inclusive); and the heavily doped P-type GaAs layer 72 having a doping concentration of 1E19 cm -3 and above (specifically, the dopant is Mg, with a doping concentration of 1E19-2E20 cm -3 , inclusive).

[0109] S10, forming a second N-type confinement layer 81 on the surface of the tunnel junction 7;

[0110] Optionally, the second N-type confinement layer 81 comprises an N-type AlGaAs confinement layer.

[0111] Specifically, an AlGaAs material layer is grown, with an Al component between 15% and 50%, a thickness between 0.1 and 0.6 μm, and an N-type dopant source (which can be a Si or Te dopant source) incorporated therein, with a carrier concentration of 4E17 / cm 3 -3E18 / cm 3 ; to obtain an N-type AlGaAs confinement layer.

[0112] S11, forming a second active region 82 on the surface of the second N-type confinement layer 81;

[0113] Optionally, the second active region 82 comprises an InGaAs / AlGaAsP active layer.

[0114] Specifically, the temperature is maintained at 600-800 °C, and the InGaAs / AlGaAsP structure is grown by controlling the TMAl source, the TMIn source and the PH3 source, wherein the InGaAs is a potential well material layer 82.1, and the AlGaAsP is a potential barrier material layer 82.2; the InGaAs / AlGaAsP structure is repeatedly grown for 4-12 pairs, and no doping source is introduced to obtain the second active region 82.

[0115] S12, forming a second P-type confinement layer 83 on the surface of the second active region 82;

[0116] Optionally, the second P-type confinement layer 83 comprises a P-type AlGaAs confinement layer.

[0117] Specifically, an AlGaAs material layer is grown, the Al component is between 15% and 50%, the thickness is between 0.1 and 0.6 μm, and a P-type doping source (which can be a Mg / C / Zn doping source) is doped, and the carrier concentration is 4E17 / cm 3 -1E18 / cm 3 ; to obtain the P-type AlGaAs confinement layer.

[0118] S13, forming a second light-absorbing layer 9 on the surface of the second P-type confinement layer 83, the second light-absorbing layer 9 comprising an AlGaAs / GaAs heterostructure.

[0119] On the basis of the above embodiment, in an embodiment of the present application, the second light-absorbing layer 9 comprises an AlGaAs layer and a GaAs layer which are stacked in the first direction.

[0120] On the basis of the above embodiment, in an embodiment of the present application, in the second light-absorbing layer 9, the band gap of the AlGaAs layer gradually changes. Optionally, the AlGaAs layer comprises an Al y Ga 1-y As layer with a gradually changing aluminum component, 0.01 < y < 0.1, and y gradually decreases along the first direction.

[0121] On the basis of the above embodiment, in an embodiment of the present application, in the second light-absorbing layer 9, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

[0122] On the basis of the above embodiment, in an embodiment of the present application, in the second light-absorbing layer 9, the thickness of the AlGaAs layer is between 1 μm and 3 μm, inclusive, and the thickness of the GaAs layer is between 0.5 μm and 2 μm, inclusive.

[0123] S14, forming a P-type window layer 10 on the surface of the second light-absorbing layer 9; optionally, the window layer comprises a P-type GaP window layer.

[0124] Specifically, the temperature is raised to 600-800°C, the TMAl source and the AsH3 source are closed, a GaP material layer is grown, the thickness of which is between 0.1-4 μm, and a P-type doping source (which can be a Mg / C / Zn doping source) is incorporated, the carrier concentration of which is 0.5E18 / cm 3 -4E19 / cm 3 ; to obtain the P-type GaP window layer.

[0125] The present application also provides an infrared LED chip, comprising:

[0126] a substrate 1 is peeled off from the double-junction infrared LED epitaxial structure according to claim 10 to expose the N-type ohmic contact layer 4;

[0127] a metal mirror is laminated on a side surface of the window layer away from the second epitaxial structure 8;

[0128] a bonding layer is arranged on a side surface of the metal mirror away from the window layer;

[0129] a substrate is arranged on a side surface of the bonding layer away from the metal mirror;

[0130] a P-type electrode is arranged on a side surface of the substrate away from the bonding layer;

[0131] an N-type electrode is laminated on a side surface of the N-type ohmic contact layer 4 away from the first light-absorbing layer 5.

[0132] Via the technical solution, the double-junction infrared LED epitaxial structure provided by the application is provided by arranging: a first epitaxial structure 6, a tunnel junction 7, a second epitaxial structure 8 and a window layer which are stacked in sequence, the first direction is perpendicular to the substrate 1 and is directed from the substrate 1 to the first epitaxial structure 6; wherein a first light-absorbing layer 5 is arranged on a side surface of the first epitaxial structure 6 close to the substrate 1, and a second light-absorbing layer 9 is arranged on a side of the second epitaxial structure 8 close to the window layer; the first light-absorbing layer 5 comprises an AlGaAs / GaAs heterostructure, and the second light-absorbing layer 9 comprises an AlGaAs / GaAs heterostructure. In the application, the light-absorbing layers (the first light-absorbing layer 5 and the second light-absorbing layer 9) are arranged on the two side surfaces of the double-junction infrared LED epitaxial structure, the light-absorbing layers comprise AlGaAs / GaAs heterostructures, and the band gap energy is slightly lower than the photon energy emitted by the active regions of the two junctions; based on this, the “useless” infrared photons emitted from the active regions and propagating to the two sides of the device can be effectively absorbed by the two light-absorbing layers; specifically, for visible red light (620-750 nm), the photon energy is higher than the band gap of AlGaAs, and the red light is strongly absorbed by the layer and cannot escape to the outside of the device, thereby eliminating “red exposure”. At the same time, the first / second light-absorbing layer 9 is located on the path of current injection, and the heterojunction interface formed by AlGaAs / GaAs can provide an additional potential barrier, effectively limiting the carriers (electrons and holes) in the respective active regions, preventing them from excessively diffusing to the non-light-emitting area and causing non-radiative recombination, and further guaranteeing high internal quantum efficiency. Secondly, the two light-emitting epitaxial structures (the first epitaxial structure 6 and the second epitaxial structure 8) are connected in series through the tunnel junction technology, based on which, under the driving of an external voltage, the remaining electrons and holes that do not emit light in the first epitaxial structure 6 will be injected into the second epitaxial structure 8 through a very thin potential barrier layer by the tunnel effect with the help of the designed built-in electric field and the tunnel layer, and emit a second photon by secondary recombination. This process realizes the secondary utilization of carriers, which significantly improves the internal quantum efficiency (IQE) and the power conversion efficiency under the same driving current, so as to improve the total light output power (brightness) of the device, thereby well compensating for the brightness loss problem caused by the first and second light-absorbing layers 9, and finally realizing net gain.

[0133] Furthermore, by setting "the first light-absorbing layer 5 to include GaAs and AlGaAs layers stacked sequentially along the first direction", the wide bandgap material (AlGaAs layer) serves as the first line of defense, preferentially absorbing the highest energy photons near the active region of the first epitaxial structure 6, reducing the nonradiative recombination probability of the highest energy photons, thereby solving the problem of localized temperature rise affecting device reliability; the narrow bandgap material (GaAs) serves as the second line of defense, performing fine filtering, so that the lowest energy target infrared photons (such as 940nm wavelength photons) can successively pass through the AlGaAs and GaAs layers and exit the chip.

[0134] Similarly, by setting "the second light-absorbing layer 9 to include AlGaAs layers and GaAs layers stacked sequentially along the first direction", the wide bandgap material (AlGaAs layer) serves as the first line of defense, preferentially absorbing the highest energy photons near the active region of the second epitaxial structure 8, reducing the nonradiative recombination probability of the highest energy photons, thereby solving the problem of local temperature rise caused by it affecting device reliability; the narrow bandgap material (GaAs) serves as the second line of defense, performing fine filtering, so that the lowest energy target infrared photons (such as photons with a wavelength of 940nm) can pass through the AlGaAs and GaAs layers successively and be emitted from the chip.

[0135] Next, by setting "in the first light-absorbing layer 5, the bandgap of the AlGaAs layer is gradually varied, optionally, the AlGaAs layer comprises Al with a gradually varying aluminum composition". x Ga 1-x As, 0.01 < x ≤ 0.1, x gradually increases along the first direction" or "In the second light-absorbing layer 9, the bandgap of the AlGaAs layer gradually changes." Optionally, the AlGaAs layer comprises Al with a gradually changing aluminum composition. y Ga 1-y As layer, 0.01 < y ≤ 0.1, y gradually decreases along the first direction, which can realize smooth carrier transport and significantly reduce voltage loss and heat generation.

[0136] The present invention also provides an infrared LED chip, which is obtained based on the above-mentioned double-junction infrared LED epitaxial structure and has the above-mentioned beneficial effects.

[0137] Example 2

[0138] like Figure 7 As shown, the difference between this embodiment and embodiment 1 is that the light-absorbing layer (i.e., the first light-absorbing layer 5) of the dual-junction infrared LED epitaxial structure provided in this embodiment is only disposed on the surface of the first epitaxial structure 6 near the substrate 1. Its preparation method can refer to the preparation method shown in embodiment 1 and omit the relevant steps of the second light-absorbing layer 9.

[0139] Example 3

[0140] like Figure 8 As shown, the difference between this embodiment and embodiment 1 is that the light-absorbing layer (i.e., the second light-absorbing layer 9) of the dual-junction infrared LED epitaxial structure provided in this embodiment is only disposed on the side surface of the second epitaxial structure 8 near the window layer. Its preparation method can refer to the preparation method shown in embodiment 1 and omit the relevant steps of the first light-absorbing layer.

[0141] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0142] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes the aforementioned element.

[0143] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A double junction infrared LED epitaxial structure, characterized in that, Comprising: a substrate; a first epitaxial structure, a tunnel junction, a second epitaxial structure and a window layer stacked in sequence along a first direction, the first direction being perpendicular to the substrate and pointing from the substrate to the first epitaxial structure; a light absorption layer, the light absorption layer being disposed on a side surface of the first epitaxial structure close to the substrate or the light absorption layer being disposed on a side surface of the second epitaxial structure close to the window layer; the light absorption layer comprising an AlGaAs / GaAs heterostructure.

2. The dual junction infrared LED epitaxial structure of claim 1, wherein, A first light absorption layer is disposed on a side surface of the first epitaxial structure close to the substrate, and a second light absorption layer is disposed on a side surface of the second epitaxial structure close to the window layer; the first light absorption layer comprises an AlGaAs / GaAs heterostructure, and the second light absorption layer comprises an AlGaAs / GaAs heterostructure.

3. The dual junction infrared LED epitaxial structure of claim 1, wherein, The first light absorption layer comprises a GaAs layer and an AlGaAs layer stacked in sequence along the first direction.

4. The dual junction infrared LED epitaxial structure of claim 1, wherein, The second light absorption layer comprises an AlGaAs layer and a GaAs layer stacked in sequence along the first direction.

5. The dual junction infrared LED epitaxial structure of claim 3, wherein, In the first light absorption layer, the band gap of the AlGaAs layer is graded.

6. The dual junction infrared LED epitaxial structure of claim 3, wherein, In the first light absorption layer, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

7. The dual junction infrared LED epitaxial structure of claim 4, wherein, In the second light absorption layer, the band gap of the AlGaAs layer is graded.

8. The dual junction infrared LED epitaxial structure of claim 4, wherein, In the second light absorption layer, the thickness of the AlGaAs layer is not less than the thickness of the GaAs layer.

9. The dual junction infrared LED epitaxial structure of claim 4, wherein, An N-type ohmic contact layer is disposed between the substrate and the first light absorption layer.

10. The double junction infrared LED epitaxial structure according to any of claims 1 to 9, wherein, The first epitaxial structure comprises a first N-type confinement layer, a first active region and a first P-type confinement layer stacked in sequence along the first direction; The second epitaxial structure comprises a second N-type confinement layer, a second active region and a second P-type confinement layer stacked in sequence along the first direction; The tunnel junction comprises a heavily doped N-type layer and a heavily doped P-type layer stacked in sequence along the first direction.

11. An infrared LED chip, characterized by Comprising: stripping the substrate from the double-junction infrared LED epitaxial structure of claim 10 to expose the N-type ohmic contact layer; a metal mirror stacked on a side surface of the window layer away from the second epitaxial structure; a bonding layer disposed on a side surface of the metal mirror away from the window layer; a substrate disposed on a side surface of the bonding layer away from the metal mirror; a P-type electrode disposed on a side surface of the substrate away from the bonding layer; an N-type electrode stacked on a side surface of the N-type ohmic contact layer away from the first light absorption layer.

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