Light emitting semiconductor device and method of manufacturing the same

Abstract

The application provides a light-emitting semiconductor device and a preparation method thereof; in the application, a second-type semiconductor layer comprises, from bottom to top, a second-type confinement layer, a second-type current spreading layer, a second buffer layer, a transition layer, a cutoff layer, and a second-type ohmic contact layer. In this way, the second buffer layer, the transition layer, and the cutoff layer with a gradually changed lattice constant gradient arranged between the second-type current spreading layer and the second-type ohmic contact layer can adjust the lattice constant at the interface between the second-type current spreading layer and the second-type ohmic contact layer from a previous abrupt change to a gradient match, thereby avoiding the stress caused by the lattice mismatch between the second-type current spreading layer and the second-type ohmic contact layer in the epitaxial growth process of the second-type semiconductor layer, the problem that the two cannot perform high-quality epitaxial growth, and finally improving the light-emitting efficiency of the light-emitting semiconductor device (LED).

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a light-emitting semiconductor device and its fabrication method. Background Technology

[0002] Infrared light-emitting diodes (IR LEDs) are semiconductor devices that emit infrared light, offering advantages such as low power consumption, long lifespan, small size, and high stability. Since their initial development in the 1960s, infrared LED technology has continuously evolved, with performance improvements and expanding applications. Currently, infrared LEDs are widely used in remote controls, infrared sensing, security monitoring, night vision systems, medical equipment, facial recognition, and industrial automation, among other fields.

[0003] With advancements in materials science and microelectronics technology, the efficiency, brightness, and response speed of infrared LEDs are continuously improving, and they will play an increasingly important role in fields such as the Internet, artificial intelligence, and intelligent transportation in the future.

[0004] Currently, the semiconductor layer in infrared light-emitting diodes consists of an AlGaAs current spreading layer and a GaP ohmic contact layer. However, there is a lattice mismatch between AlGaAs and GaP materials, which prevents the AlGaAs current spreading layer and GaP ohmic contact layer from being epitaxially grown and bonded with high quality. Summary of the Invention

[0005] One objective of this application is to provide a light-emitting semiconductor device to alleviate the stress caused by lattice mismatch during epitaxial growth in a type II semiconductor layer, thereby improving the luminous efficiency of the light-emitting semiconductor device (LED).

[0006] To achieve the above objectives, one embodiment of this application provides a light-emitting semiconductor device, which, from bottom to top, comprises: a substrate, a first type semiconductor layer, an active layer, and a second type semiconductor layer; wherein, the second type semiconductor layer, from bottom to top, comprises a second type confinement layer, a second type current spreading layer, a second buffer layer, a transition layer, a cutoff layer, and a second type ohmic contact layer, and the second buffer layer is Al. j Ga k As x P y Layer, where 0.025≤j≤0.1, 0.4≤k≤0.475, 0.1≤x≤0.2, 0.3≤y≤0.4, and j+k=0.5, x+y=0.5.

[0007] Optionally, the second type current spreading layer and the second buffer layer both contain Al, Ga, and As elements; the second buffer layer and the transition layer both contain Ga, As, and P elements; the transition layer and the cutoff layer both contain Ga and P elements; and the cutoff layer and the second type ohmic contact layer both contain Ga and P elements.

[0008] Optionally, the defect density of the stop layer is greater than the defect density of the second type of ohmic contact layer.

[0009] Optionally, the composition of Al and As elements in the second buffer layer gradually decreases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer, while the composition of Ga and P elements in the second buffer layer gradually increases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer.

[0010] Optionally, the composition of the second buffer layer that is in direct contact with the second type of current spreading layer is Al. 0.25 Ga 0.25 As 0.25 P 0.25 .

[0011] Optionally, the lattice constant of the second buffer layer gradually decreases from the side closer to the second type current spreading layer to the side farther away from the second type current spreading layer.

[0012] Optionally, the transition layer is Ga. 0.5 (As) m P 1-m ) 0.5 The layers are such that 0.05 < m < 0.4;

[0013] Optionally, the cutoff layer is a GaP layer.

[0014] Optionally, the second type current spreading layer is an AlGaAs layer, and the second type ohmic contact layer is a GaP layer.

[0015] Optionally, the elemental composition of the second buffer layer remains unchanged.

[0016] Optionally, the composition of the second buffer layer is Al. 0.25 Ga 0.25 As 0.25 P 0.25 .

[0017] Optionally, the thickness of the second buffer layer is 10nm~100nm.

[0018] Optionally, the thickness of the transition layer is 10nm~50nm.

[0019] Optionally, the thickness of the stop layer is 10nm~50nm.

[0020] Optionally, the second buffer layer is doped with a type II dopant, wherein the type II dopant is at least one of magnesium and zinc.

[0021] Optionally, the dopant types in the transition layer and the stop layer are the same as the dopant types in the second buffer layer.

[0022] Optionally, the first type of semiconductor layer includes, from bottom to top, a first type of ohmic contact layer, a first type of current spreading layer, and a first type of confinement layer.

[0023] Optionally, the active layer comprises, from bottom to top, a first barrier layer, a multi-quantum well layer, and a second barrier layer.

[0024] Optionally, the multi-quantum well layer is a periodic structure formed by alternating growth of well layers and barrier layers.

[0025] Optionally, the number of periods in the multi-quantum well layer is 6 to 30.

[0026] Optionally, the light-emitting semiconductor device may further include: a first buffer layer, the first buffer layer being located between the substrate and the first type of semiconductor layer.

[0027] To achieve the above objectives, one embodiment of this application also provides a method for fabricating a light-emitting semiconductor device, comprising:

[0028] Provide substrate;

[0029] A first-type semiconductor layer and an active layer are sequentially grown on the substrate;

[0030] A second type semiconductor layer is grown on the active layer; wherein, from bottom to top, the second type semiconductor layer includes a second type confinement layer, a second type current spreading layer, a second buffer layer, a transition layer, a cutoff layer, and a second type ohmic contact layer, and the second type buffer layer is Al. j Ga k As x P y Layer, where 0.025≤j≤0.1, 0.4≤k≤0.475, 0.1≤x≤0.2, 0.3≤y≤0.4, and j+k=0.5, x+y=0.5.

[0031] Optionally, the second type current spreading layer and the second buffer layer both contain Al, Ga, and As elements; the second buffer layer and the transition layer both contain Ga, As, and P elements; the transition layer and the cutoff layer both contain Ga and P elements; and the cutoff layer and the second type ohmic contact layer both contain Ga and P elements.

[0032] Optionally, the defect density of the stop layer is greater than the defect density of the second type of ohmic contact layer.

[0033] Optionally, the composition of Al and As elements in the second buffer layer gradually decreases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer, while the composition of Ga and P elements in the second buffer layer gradually increases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer.

[0034] Optionally, the composition of the second buffer layer that is in direct contact with the second type of current spreading layer is Al. 0.25 Ga 0.25 As 0.25 P 0.25 .

[0035] Optionally, the lattice constant of the second buffer layer gradually decreases from the side closer to the second type current spreading layer to the side farther away from the second type current spreading layer.

[0036] Optionally, the transition layer is Ga. 0.5 (As) m P 1-m ) 0.5 The cutoff layer is a GaP layer, and 0.05 < m < 0.4.

[0037] Optionally, the second type current spreading layer is an AlGaAs layer, and the second type ohmic contact layer is a GaP layer.

[0038] Optionally, the elemental composition of the second buffer layer remains unchanged.

[0039] Optionally, the thickness of the second buffer layer is 10nm~100nm.

[0040] Optionally, the thickness of the transition layer is 10nm~50nm.

[0041] Optionally, the thickness of the stop layer is 10nm~50nm.

[0042] The light-emitting semiconductor device provided in this application has a second buffer layer, a transition layer and a stop layer sandwiched between the second type current spreading layer and the second type ohmic contact layer. By utilizing the fact that adjacent film layers in the stacked film structure of the second type semiconductor layer contain the same elements, the elements in the second type current spreading layer and the second type ohmic contact layer can be smoothly transitioned. This reduces the stress caused by lattice mismatch between the second type current spreading layer and the second type ohmic contact layer, which prevents them from undergoing high-quality epitaxial growth. Ultimately, this also improves the luminous efficiency of the light-emitting semiconductor device (LED).

[0043] Secondly, since the second buffer layer is Al j Ga k As x P y Therefore, compared to the second current spreading layer using AlGaInP material in the prior art, the second buffer layer and the second type ohmic contact layer in this application have a higher lattice matching degree. The band gap and band shift of the second buffer layer are easier to achieve, allowing for a smooth transition of elements from the second current spreading layer to the second type ohmic contact layer. Furthermore, since the second type ohmic contact layer does not contain In, it can also avoid the problem of interdiffusion at the interface between the second current spreading layer and the second type ohmic contact layer caused by the presence of In, such as the element mixing at the junction of the second current spreading layer and the second type ohmic contact layer to form AlGaInAsP material. Compared to the second current spreading layer using AlGaP material in the prior art, AlGaP material tends to have an indirect band gap, which is not conducive to light emission. The second buffer layer in this application obtains more flexible band control by introducing As element, thereby realizing the conversion from indirect band gap to direct band gap. Moreover, the lattice mismatch between AlGaP material and AlGaAs is large, making it easier to generate through dislocations. That is, the method of this application can ultimately effectively improve the luminous efficiency of light-emitting semiconductor devices (LEDs).

[0044] Furthermore, since adjacent layers in the stacked film structure of the second type semiconductor layer contain the same elements, and the elements contained in the film layer and their composition are related to the lattice constant of the film material, the lattice constants of the second type current spreading layer and the second buffer layer are similar, the lattice constants of the second buffer layer and the transition layer are similar, the lattice constants of the transition layer and the cutoff layer are similar, and the lattice constants of the cutoff layer and the second type ohmic contact layer are similar. This results in a gradient change in the lattice constant of the stacked film structure of the second type semiconductor layer from bottom to top. In other words, the lattice constant at the interface between the second type current spreading layer and the second type ohmic contact layer is adjusted from abrupt change to gradient matching. This means that the huge stress originally concentrated at a single interface between the second type current spreading layer and the second type ohmic contact layer is dispersed into the second buffer layer, the transition layer, and the cutoff layer for gradual release. This effectively reduces the lattice mismatch between the second type current spreading layer and the second type ohmic contact layer, avoiding the stress caused by lattice mismatch between the second type current spreading layer and the second type ohmic contact layer, thereby improving the luminous efficiency of the light-emitting semiconductor device (LED).

[0045] Furthermore, by adjusting the fabrication process parameters (e.g., temperature) of the stop layer, the defect density of the stop layer can be made greater than that of the second type ohmic contact layer, thereby preventing the defects of the second buffer layer and transition layer from being transmitted to the second type ohmic contact layer, i.e., stopping the transmission of defects. Attached Figure Description

[0046] The accompanying drawings provide a more in-depth understanding of embodiments of this application and are incorporated herein by reference as a whole. These drawings and descriptions are used to illustrate the principles of some embodiments. It should be noted that all drawings are schematic diagrams and are for illustrative and drawing convenience, and relative sizes and proportions have been adjusted. The same symbols represent corresponding or similar features in different embodiments.

[0047] Figure 1 The diagram illustrates the structure of a light-emitting semiconductor device in one embodiment of this application.

[0048] Figure 2 The illustration shows a fabrication flowchart of a light-emitting semiconductor device according to an embodiment of this application.

[0049] exist Figures 1 to 2 middle:

[0050] 100 - Substrate, 110 - First buffer layer, 120 - First type semiconductor layer, 130 - Active layer, 131 - First barrier layer, 132 - Multiple quantum well layer, 133 - Second barrier layer, 140 - Second type semiconductor layer, 141 - Second type confinement layer, 142 - Second type current spreading layer, 143 - Second buffer layer, 144 - Transition layer, 145 - Cut-off layer, 146 - Second type ohmic contact layer.

[0051] In the accompanying drawings, the same parts are referred to by the same reference numerals, and the drawings are not drawn to scale. Detailed Implementation

[0052] To make the technical solutions and advantages of the embodiments of this application clearer, the technical solutions of this application will be further described in detail below with reference to the accompanying drawings and embodiments. Although exemplary implementation methods of this application are shown in the accompanying drawings, it should be understood that this application can be implemented in various forms and should not be limited to the implementation methods described herein. Rather, these implementation methods are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0053] Before describing the embodiments according to this application, the following points should be explained in advance. First, in this specification, when only "GaInP" is used, it refers to any compound in which the chemical composition ratio of the sum of Ga and In to P is 1:1, and the ratio of Ga to In is not fixed. When only "AlGaInP" is used, it refers to any compound in which the chemical composition ratio of the sum of Al, Ga, and In to P is 1:1, and the ratio of Al, Ga, and In is not fixed. Furthermore, when only "AlInP" is used, it refers to any compound in which the chemical composition ratio of the sum of Al and In to P is 1:1, and the ratio of Al to In is not fixed.

[0054] Figure 1 This is a schematic diagram of the structure of a light-emitting semiconductor device according to an embodiment of this application.

[0055] See Figure 1 The light-emitting semiconductor device comprises, from bottom to top, a substrate 100, a first type semiconductor layer 120, an active layer 130, and a second type semiconductor layer 140; wherein, the second type semiconductor layer 140 comprises, from bottom to top, a second type confinement layer 141, a second type current spreading layer 142, a second buffer layer 143, a transition layer 144, a cutoff layer 145, and a second type ohmic contact layer 146 stacked sequentially.

[0056] The substrate 100 can be a transparent insulating substrate. More specifically, the substrate 100 is preferably a GaAs (gallium arsenide) substrate, but can also be a Si (silicon) substrate, though not limited thereto. Furthermore, the light-emitting semiconductor device of this embodiment may also include a first buffer layer 110. The first buffer layer 110 is located between the substrate 100 and the first-type semiconductor layer 120, and the first buffer layer 110 can minimize the impact of surface defects of the substrate 100 on the light-emitting semiconductor device, reduce defects and dislocations in the light-emitting semiconductor device, and provide a smooth interface for the next growth step. The material of the first buffer layer 110 is preferably GaAs, and the thickness of the first buffer layer 110 is preferably 100nm-600nm, for example, 300nm, but not limited thereto. The first buffer layer 110 is doped with a first-type dopant, such as an n-type dopant, which can be at least one of silicon (Si) and tellurium (Te), but is not limited thereto. More specifically, the first-type dopant is preferably silicon (Si).

[0057] The first type semiconductor layer 120 is located on the first buffer layer 110 and can be an N-type semiconductor layer. It comprises, from bottom to top, a first type ohmic contact layer 121 (also called an n-type ohmic contact layer), a first type current spreading layer 122 (also called an n-type current spreading layer), and a first type confinement layer 123 (also called an n-type confinement layer). Specifically, the first type ohmic contact layer 121 is located on the first buffer layer 110, and its material is preferably InGaAs or GaAs, and preferably GaAs, but not limited thereto. In this embodiment, the thickness of the first type ohmic contact layer 121 is preferably 20nm-200nm, for example, 100nm. Furthermore, the first type ohmic contact layer 121 is doped with a first type dopant, such as an n-type dopant. The n-type dopant can be one of silicon (Si) and tellurium (Te), and preferably silicon (Si), but not limited thereto. The first type current spreading layer 122 is located on the first type ohmic contact layer 121, and its material is preferably AlGaAs, but not limited thereto. In this embodiment, the thickness of the first type current spreading layer 122 is preferably 3µm to 8µm, for example, 5µm. Furthermore, the first type current spreading layer 122 is also doped with a first type dopant, such as an n-type dopant, which can be at least one of silicon (Si) and tellurium (Te), and is preferably silicon (Si), but not limited thereto. The first type confinement layer 123 is located on the first type current spreading layer 122, and its material is preferably AlGaAs, but not limited thereto. In this embodiment, the thickness of the first type confinement layer 123 is preferably 200nm-1000nm, for example, 400nm. Furthermore, the first type confinement layer 123 is also doped with a first type dopant, such as an n-type dopant, which can be at least one of silicon (Si) and tellurium (Te), and is preferably silicon (Si), but not limited thereto.

[0058] The active layer 130 is located on the first type semiconductor layer 120 and is a composite film structure. Specifically, the active layer 130 includes, from bottom to top, a first barrier layer 131, a multiple quantum well layer 132, and a second barrier layer 133 in a vertical direction. The first barrier layer 131 is preferably made of AlGaAs, but is not limited to this. The first barrier layer 131 is an unintentionally doped layer. The thickness of the first barrier layer 131 is preferably 200nm to 800nm, for example, 300nm. Further, the multiple quantum well layer 132 is located on the first barrier layer 131, and is preferably made of InGaAs / AlGaAs, i.e., preferably a periodic structure formed by alternating well and barrier layers. The number of periods of the multiple quantum well layer 132 is preferably 6 to 30, i.e., the multiple quantum well layer 132 preferably has 6 to 30 pairs of well and barrier layers, for example, a multiple quantum well layer 132 with 12 periods, i.e., 12 pairs of well and barrier layers. The thickness of the multiple quantum well layer 132 is preferably 50 nm to 2000 nm, for example, 900 nm. The second barrier layer 133 is located on the multiple quantum well layer 132, and its material is preferably AlGaAs, but not limited thereto. The second barrier layer 133 is an unintentionally doped layer, and its thickness is preferably 200 nm to 800 nm, for example, 300 nm. In this way, the first barrier layer 131 and the second barrier layer 133 in the active layer 130 can be used to block electrons, reduce the leakage of electrons in the charge carriers, and better confine most electrons and holes in the multiple quantum well layer 132 in the active layer 130, thereby improving the radiative recombination efficiency and ultimately improving the luminous efficiency of the light-emitting semiconductor device (LED).

[0059] The second type semiconductor layer 140 is located on the active layer 130, and the doping type of the second type semiconductor layer 140 is opposite to that of the first type semiconductor layer 120. For example, the first type semiconductor layer is an N-type semiconductor layer, while the second type semiconductor layer 140 is a P-type semiconductor layer. The second type semiconductor layer 140 may include, from bottom to top in the vertical direction, the following: a second type confinement layer 141, a second type current spreading layer 142, a second buffer layer 143, a transition layer 144, a stop layer 145, and a second type ohmic contact layer 146.

[0060] Specifically, the second type confinement layer 141 is located on the active layer 130, and its material is preferably AlGaAs, but not limited thereto. In this embodiment, the thickness of the second type confinement layer 141 is preferably 200nm-1000nm, for example, 400nm. Furthermore, the second type confinement layer 141 is doped with a second type dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), and preferably magnesium (Mg), but not limited thereto. The second type current spreading layer 142 is located on the second type confinement layer 141, and its material is preferably AlGaAs, but not limited thereto. Furthermore, the second type current spreading layer 142 is also doped with a second type dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), and preferably magnesium (Mg), but not limited thereto. In this embodiment, the thickness of the second type current spreading layer 142 is preferably 200nm-3000nm, for example, 1000nm. The second buffer layer 143 is located on the second type current spreading layer 142, and the second type ohmic contact layer 146 is located on the second buffer layer 143.

[0061] In this embodiment, after forming the second type current spreading layer 142, the second type ohmic contact layer 146 is not formed directly. Instead, a composite film structure is formed between them, namely, a second buffer layer 143, a transition layer 144, and a stop layer 145. The second buffer layer 143 is located on the second type current spreading layer 142, the transition layer 143 is located on the second buffer layer 143, the stop layer 144 is located on the transition layer 143, and finally, the second type ohmic contact layer 146 is located on the stop layer 145. In this embodiment, the second buffer layer 143 is Al. j Ga k As x P y The second buffer layer 143 has a thickness ranging from 10 nm to 100 nm, for example, 50 nm. Furthermore, the second buffer layer 143 is doped with a type II dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), preferably Mg, but not limited thereto. The thickness of the second buffer layer 143 is 0.025 ≤ j ≤ 0.1, 0.4 ≤ k ≤ 0.475, 0.1 ≤ x ≤ 0.2, 0.3 ≤ y ≤ 0.4, and j + k = 0.5, x + y = 0.5.

[0062] In this embodiment, the composition of the elements contained in the second buffer layer 143 can remain constant or change, and this application preferably specifies that the composition of the elements contained in the second buffer layer 143 changes. Specifically, the growth of the second buffer layer 143 is preferably carried out in the reaction chamber of an MOCVD growth furnace, and the material composition changes during the growth process from the start to the end; for example, the composition of the second buffer layer 143 gradually changes such that the composition of Al and As elements gradually decreases from the side closer to the second type current spread layer 142 to the side farther away from the second type current spread layer 142, while the composition of Ga and P elements gradually changes (increases) from the side closer to the second type current spread layer 142 to the side farther away from the second type current spread layer 142. For example, the initial composition of the second buffer layer 143 can be Al. 0.25 Ga 0.25 As 0.25 P 0.25 The component at the end of growth is Al j Ga k As x P y Wherein, 0.025 < j < 0.1, 0.4 < k < 0.475, 0.1 < x < 0.2, 0.3 < y < 0.4, and j + k = 0.5, x + y = 0.5, preferably, j = 0.05, k = 0.45, x = 0.15, y = 0.35.

[0063] Since the elemental composition of the second buffer layer 142 in this application can gradually change along the direction from the side close to the second type current spreading layer 142 to the side away from the second type current spreading layer 142, and the elemental composition is related to the lattice constant of the film material, the lattice constant of the second buffer layer 143 at different thickness positions along the direction from the side close to the second type current spreading layer 142 to the side away from the second type current spreading layer 142 is different, that is, it gradually decreases from bottom to top along the thickness direction; thus, the lattice constant and elemental composition of the second buffer layer 143 near the second type current spreading layer 142 are different from those of the second type current spreading layer 142. The lattice constant and elements of the material are brought closer together. Then, a transition layer 144 is formed. Since the lattice constant of the GaAsP material in the transition layer 144 is 5.46~5.53, which is close to that of the GaP material in the second type ohmic contact layer 146, the transition of lattice constant and material elements is further completed. Then, a stop layer 145 with GaP material is grown. Taking advantage of the fact that the defect density of the stop layer 145 is greater than that of the second type ohmic contact layer 146, the residual stress and defects in the second buffer layer 143 and the transition layer 144 are annihilated in the stop layer 145, which provides an excellent growth platform for the subsequent epitaxial growth of the second type ohmic contact layer 146.

[0064] It should be noted that in other embodiments, since a second buffer layer 143, a transition layer 144, and a stop layer 145 are sequentially stacked between the second type current spreading layer 142 and the second type ohmic contact layer 146, and the second type current spreading layer 142 and the second buffer layer 143 contain the same elements, the second buffer layer 143 and the transition layer 144 contain the same elements, the transition layer 144 and the stop layer 145 contain the same elements, and the stop layer 145 and the second type ohmic contact layer 146 contain the same elements, the elements in the second type current spreading layer 142 to the second type ohmic contact layer 146 can be smoothly transitioned by utilizing the fact that adjacent layers in the stacked film structure of the second type semiconductor layer 140 contain the same elements. Therefore, even if the elemental composition of the second buffer layer 142 remains unchanged along the direction from the side close to the second type current spreading layer 142 to the side away from the second type current spreading layer 142, the purpose of this application can still be achieved.

[0065] The transition layer 144 is located on the second buffer layer 143, and is preferably GaAsP, Ga 0.5 (As) m P 1-m The transition layer 144 has a thickness of 0.5 nm, where 0.05 < m < 0.4, and more preferably m = 0.1. The transition layer 144 is also doped with a type II dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), preferably magnesium (Mg), but not limited thereto. The thickness of the transition layer 144 is preferably 10 nm to 50 nm, for example, 20 nm. The stop layer 145 is located on the transition layer 144, and the material is preferably GaP. The stop layer 145 is also doped with a type II dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), and also preferably magnesium (Mg), but not limited thereto. Furthermore, the thickness of the stop layer 145 is preferably 10 nm to 50 nm, for example, 20 nm. In this embodiment, by adjusting the parameters of the preparation process of the cutoff layer 145, such as adjusting the temperature in the reaction chamber of the MOCVD growth furnace, the growth mode of the cutoff layer 145 can be made to be low temperature and low speed growth, thereby controlling the defect density of the cutoff layer 145 to be greater than the defect density of the second type ohmic contact layer 146, preventing the defects generated during the growth of the second buffer layer 143 and the transition layer 144 from being transmitted to the second type ohmic contact layer 146, thus achieving the function of stopping defect transmission.

[0066] The material of the second type ohmic contact layer 146 is preferably GaP. Obviously, since the material of the second type current spreading layer 142 in the second semiconductor layer 140 is AlGaAs and the material of the second type ohmic contact layer 146 is GaP, and the lattice mismatch of AlGaAs (lattice constant between 5.65 and 5.66) and GaP (lattice constant between 5.45) is between 3.6% and 3.8%, this will inevitably make it difficult for the two to achieve high-quality epitaxial growth and bonding, that is, a large number of growth defects will be generated during the epitaxial growth process, which will ultimately seriously affect the performance of the light-emitting semiconductor device.

[0067] It is understood that the lattice constant of AlGaAs material can change with the composition. Therefore, in this embodiment, the lattice constant and material elements of the second buffer layer 143 are gradually brought closer to GaP material by changing the elemental composition of AlGaAsP material, for example, gradually decreasing the composition of Al and As elements and gradually increasing the composition of Ga and P elements. Then, the transition layer 144 is connected. Since the lattice constant of GaAsP material in the transition layer 144 is 5.46~5.53, which is close to that of GaP material, the transition of lattice constant and material elements is further completed. Then, the residual stress and defects are annihilated by growing a stop layer 145 made of GaP material, providing an excellent growth platform for the subsequent epitaxial growth of the second type ohmic contact layer 146.

[0068] Figure 2 This is a flowchart illustrating the fabrication process of a light-emitting semiconductor device in one embodiment of this application.

[0069] See Figure 2 , Figure 2 The fabrication method of the light-emitting semiconductor device shown may specifically include the following steps:

[0070] Step S1: Provide substrate 100;

[0071] Step S2: A first buffer layer 110, a cutoff layer 120, a first type semiconductor layer 120 and an active layer 130 are sequentially grown on the substrate 100;

[0072] Step S3: Grow a second type semiconductor layer 140 on the active layer 130; wherein, the second type semiconductor layer 140 includes, from bottom to top, a second type confinement layer 141, a second type current spreading layer 142, a second buffer layer 143, a transition layer 144, a cutoff layer 145, and a second type ohmic contact layer 146, and the second type buffer layer 143 is Al. j Ga k As x P yLayer, where 0.025≤j≤0.1, 0.4≤k≤0.475, 0.1≤x≤0.2, 0.3≤y≤0.4, and j+k=0.5, x+y=0.5.

[0073] In this embodiment, the fabrication process of the light-emitting semiconductor device can be any one of metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or ultra-high vacuum chemical vapor deposition (UHVCVD), preferably MOCVD. The following specific embodiments use MOCVD as an example for illustration.

[0074] Step S1 is performed to provide a substrate 100. The substrate 100 is preferably a GaAs (gallium arsenide) substrate, but may also be a Si (silicon) substrate, but is not limited thereto.

[0075] Step S2 is performed to grow a first buffer layer 110 on the substrate 100. The first buffer layer 110 can minimize the impact of surface defects on the substrate 100 on the light-emitting semiconductor device, reduce the possibility of defects and dislocations in the light-emitting semiconductor device, and provide a smooth interface for the next growth step. The material of the first buffer layer 110 is preferably GaAs, but not limited to it. The first buffer layer 110 is doped with a type-1 dopant, such as an N-type dopant, which can be at least one of silicon (Si) and tellurium (Te), but is not limited to it. Further, the type-1 dopant is preferably silicon (Si).

[0076] The first buffer layer 110 is preferably grown in the reaction chamber of an MOCVD growth furnace to a thickness of 100 nm to 600 nm. For example, a first buffer layer 110 with a thickness of 300 nm is grown.

[0077] After the step of growing the first buffer layer 110, a first type semiconductor layer 120 is grown on the first buffer layer 110. The first type semiconductor layer 120 may sequentially include a first type ohmic contact layer 121, a first type current spreading layer 122, and a first type confinement layer 123 from bottom to top. Therefore, after the step of growing the first buffer layer 110, the first type ohmic contact layer 121 is grown on the first buffer layer 110.

[0078] The first type ohmic contact layer 121 can be made of AlGaInP or GaAs, preferably InGaAs or GaAs, and more preferably GaAs, but is not limited thereto. The first type ohmic contact layer 121 is doped with a type I dopant, such as an N-type dopant, which can be silicon (Si) or tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably silicon (Si).

[0079] The growth of the first type of ohmic contact layer 121 is preferably carried out in the reaction chamber of an MOCVD growth furnace, with a thickness of 20 nm to 200 nm. For example, a first type of ohmic contact layer 121 with a thickness of 100 nm is grown.

[0080] After the step of growing the first type ohmic contact layer 121, a first type current spreading layer 122 is grown on the first type ohmic contact layer 121. The material of the first type current spreading layer 122 is preferably AlGaAs, but not limited to this. The growth of the first type current spreading layer 122 is preferably carried out in the reaction chamber of an MOCVD growth furnace, resulting in a thickness of 3µm to 8µm. For example, a first type current spreading layer 132 with a thickness of 5µm is grown.

[0081] After the step of growing the first type current spreading layer 122, the first type confinement layer 123 is grown on the first type current spreading layer 122. The material of the first type confinement layer 123 is preferably AlGaAs, but not limited thereto. The growth of the first type confinement layer 123 is preferably: the first type confinement layer 123 with a thickness of 200nm-1000nm is grown in the reaction chamber of the MOCVD growth furnace, for example, the first type confinement layer 123 with a thickness of 400nm is grown.

[0082] After the step of growing the first type confinement layer 123, an active layer 130 is grown on the first type confinement layer 123. The active layer 130 is preferably a composite film structure, that is, the active layer 130 includes, from bottom to top in the vertical direction, a first barrier layer 131, a multiple quantum well layer 132, and a second barrier layer 133. The first barrier layer 131 is preferably made of AlGaAs, but is not limited to this. The first barrier layer 131 is preferably grown in the reaction chamber of an MOCVD growth furnace to a thickness of 200 nm to 800 nm, for example, a first barrier layer 131 with a thickness of 300 nm. Furthermore, the first barrier layer 131 is an unintentionally doped layer.

[0083] After the step of growing the first barrier layer 131, a multi-quantum well layer 132 is grown on the first barrier layer 131. The material of the multi-quantum well layer 132 is preferably InGaAs / AlGaAs, that is, it is preferably a periodic structure formed by alternating well layers and barrier layers, and the number of periods of the multi-quantum well layer 132 is preferably 6 to 30, that is, the multi-quantum well layer 132 preferably has 6 to 30 pairs of well layers and barrier layers, for example, a multi-quantum well layer 132 with 12 periods, i.e., 12 pairs of well layers and barrier layers. The growth of the multi-quantum well layer 132 is preferably: the multi-quantum well layer 132 with a thickness of 50 nm to 2000 nm is grown in the reaction chamber of an MOCVD growth furnace, for example, a multi-quantum well layer 132 with a thickness of 900 nm is grown.

[0084] After the step of growing the multi-quantum well layer 132, a second barrier layer 133 is grown on the multi-quantum well layer 132. The second barrier layer 133 is preferably made of AlGaAs and is an unintentionally doped layer. The growth of the second barrier layer 133 is preferably carried out in the reaction chamber of an MOCVD growth furnace, with a thickness of 200 nm to 800 nm, for example, growing a second barrier layer 133 with a thickness of 300 nm.

[0085] In this way, the first barrier layer 131 and the second barrier layer 133 in the active layer 130 can be used to block electrons, reduce the leakage of electrons in the charge carriers, and better confine most electrons and holes in the multi-quantum well layer 132 in the active layer 130, thereby improving the radiative recombination efficiency and ultimately improving the luminous efficiency of the light-emitting semiconductor device (LED).

[0086] Step S3 is performed to grow a second type semiconductor layer 140 on the active layer 130. The second type semiconductor 140 includes a second type confinement layer 141, a second type current spreading layer 142, a second buffer layer 143, a transition layer 144, a stop layer 145, and a second type ohmic contact layer 146. Therefore, after growing the active layer 130, the second type confinement layer 141 is grown on the active layer 130. The material of the second type confinement layer 141 is preferably AlGaAs, but not limited thereto. The growth of the second type confinement layer 141 is preferably performed by growing a 200nm-1000nm thick second type confinement layer 141 in the reaction chamber of an MOCVD growth furnace, for example, growing a 400nm thick second type confinement layer 141. Furthermore, the second type confinement layer 141 is doped with a second type dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), and is preferably magnesium (Mg), but not limited thereto.

[0087] After the step of growing the second type confinement layer 141, a second type current spreading layer 142 is grown on the second type confinement layer 141. The material of the second type current spreading layer 142 is preferably AlGaAs, but not limited to it. The growth of the second type current spreading layer 142 is preferably carried out in the reaction chamber of an MOCVD growth furnace, with a thickness of 200 nm-3000 nm, for example, growing a second type current spreading layer 142 with a thickness of 1000 nm. Furthermore, the second type current spreading layer 142 is also doped with a second type dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), preferably magnesium (Mg), but not limited to it.

[0088] After the step of growing the second type current spreading layer 142, a second buffer layer 143 is grown on the second type current spreading layer 142; in this embodiment, the second buffer layer 143 is Al. j Ga k As x P y The second buffer layer 143 has a thickness ranging from 10 nm to 100 nm, for example, 50 nm, and is doped with a type II dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), preferably Mg, but not limited to this. The second buffer layer 143 is preferably grown in the reaction chamber of an MOCVD growth furnace, and the material composition changes during the growth process; for example, the composition of the second buffer layer 143 gradually changes, with the Al and As elements gradually decreasing and the Ga and P elements gradually increasing. For example, the initial composition of the second buffer layer 143 is Al... 0.25 Ga 0.25 As 0.25 P 0.25 The component at the end of growth is Al j Ga k As x P y Wherein, 0.025 < j < 0.1, 0.4 < k < 0.475, 0.1 < x < 0.2, 0.3 < y < 0.4, and j + k = 0.5, x + y = 0.5. Preferably, j = 0.05, k = 0.45, x = 0.15, and y = 0.35. The material of the transition layer 144 is preferably GaAsP, and the composition of the transition layer 144 is Ga... 0.5 (A) s mP 1-mThe transition layer 144 is doped with a second-type dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), but is not limited thereto. Further, the first-type dopant is preferably Mg. The transition layer 144 is preferably grown in the reaction chamber of an MOCVD growth furnace to a thickness of 10 nm to 50 nm. Preferably, a transition layer 144 with a thickness of 20 nm is grown. The material of the stop layer 145 is preferably GaP; the stop layer 145 is doped with a second-type dopant, such as a p-type dopant, which can be at least one of magnesium (Mg) and zinc (Zn), but is not limited thereto. Further, the first-type dopant is preferably Mg. The stop layer 145 is preferably grown in the reaction chamber of an MOCVD growth furnace to a thickness of 10 nm to 50 nm, and the growth method is low-temperature, low-speed growth. Preferably, a stop layer 145 with a thickness of 20 nm is grown.

[0089] After growing the stop layer 145, a second type ohmic contact layer 146 is grown on the stop layer 145. The second type ohmic contact layer 146 is used to form an ohmic contact with a metal electrode. The material of the second type ohmic contact layer 146 is preferably GaP, but not limited thereto. The second type ohmic contact layer 146 may be doped with carbon (C).

[0090] The second type ohmic contact layer 146 is preferably grown in the reaction chamber of an MOCVD growth furnace with a thickness of 20 nm to 200 nm. Preferably, a second type ohmic contact layer 146 with a thickness of 100 nm is grown.

[0091] This embodiment effectively reduces the mismatch between AlGaAs material (second-type current spreading layer 142) and GaP material (second-type ohmic contact layer 146) by adding a second buffer layer 143, a transition layer 144, and a stop layer 145 with a lattice constant gradient change between the second-type current spreading layer 142 and the second-type ohmic contact layer 146, and by including adjacent film layers with the same elements. The structure of the second buffer layer 143 and the transition layer 144 allows the lattice constant and material elements to gradually converge, and the stop layer 145 at the end annihilates the residual stress within the stop layer 145, preventing it from continuing to diffuse upwards. This results in a high-quality epitaxial structure and improves the luminous efficiency of the light-emitting semiconductor device.

[0092] In summary, the light-emitting semiconductor device provided in this application, by sandwiching a second buffer layer, a transition layer, and a stop layer sequentially stacked between the second-type current spreading layer and the second-type ohmic contact layer, utilizes the fact that adjacent layers in the bottom-to-top stacked film structure of the second-type semiconductor layer contain the same elements. This allows for a smooth transition of elements from the second-type current spreading layer to the second-type ohmic contact layer, thereby reducing the stress caused by lattice mismatch between the second-type current spreading layer and the second-type ohmic contact layer, which prevents high-quality epitaxial growth of both layers, and ultimately improves the luminous efficiency of the light-emitting semiconductor device (LED). Secondly, since the second buffer layer is Al... j Ga k As x P yTherefore, compared to the second current spreading layer using AlGaInP material in the prior art, the second buffer layer and the second type ohmic contact layer in this application have a higher lattice matching degree. The band gap and band shift of the second buffer layer are easier to achieve, allowing for a smooth transition of elements from the second current spreading layer to the second type ohmic contact layer. Furthermore, since the second type ohmic contact layer does not contain In, it can also avoid the problem of interdiffusion at the interface between the second current spreading layer and the second type ohmic contact layer caused by the presence of In, such as the element mixing at the junction of the second current spreading layer and the second type ohmic contact layer to form AlGaInAsP material. Compared to the second current spreading layer using AlGaP material in the prior art, AlGaP material tends to have an indirect band gap, which is not conducive to light emission. The second buffer layer in this application obtains more flexible band control by introducing As element, thereby realizing the conversion from indirect band gap to direct band gap. Moreover, the lattice mismatch between AlGaP material and AlGaAs is large, making it easier to generate through dislocations. That is, the method of this application can ultimately effectively improve the luminous efficiency of light-emitting semiconductor devices (LEDs). Furthermore, since adjacent layers in the stacked film structure of the second type semiconductor layer contain the same elements, and the elements contained in the film layer and their composition are related to the lattice constant of the film material, the lattice constants of the second type current spreading layer and the second buffer layer are similar, the lattice constants of the second buffer layer and the transition layer are similar, the lattice constants of the transition layer and the cutoff layer are similar, and the lattice constants of the cutoff layer and the second type ohmic contact layer are similar. This results in a gradient change in the lattice constant of the stacked film structure of the second type semiconductor layer from bottom to top. In other words, the lattice constant at the interface between the second type current spreading layer and the second type ohmic contact layer is adjusted from abrupt change to gradient matching. This means that the huge stress originally concentrated at a single interface between the second type current spreading layer and the second type ohmic contact layer is dispersed into the second buffer layer, the transition layer, and the cutoff layer for gradual release. This effectively reduces the lattice mismatch between the second type current spreading layer and the second type ohmic contact layer, avoiding the stress caused by lattice mismatch between the second type current spreading layer and the second type ohmic contact layer, thereby improving the luminous efficiency of the light-emitting semiconductor device (LED). Furthermore, by adjusting the fabrication process parameters (e.g., temperature) of the stop layer, the defect density of the stop layer can be made greater than that of the second type ohmic contact layer, thereby preventing the defects of the second buffer layer and transition layer from being transmitted to the second type ohmic contact layer, i.e., stopping the transmission of defects.

[0093] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0094] Furthermore, it is understood that although this application has disclosed preferred embodiments above, these embodiments are not intended to limit this application. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of this application based on the disclosed technical content, or equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the scope of protection of the technical solutions of this application.

[0095] Furthermore, it should be understood that this application is not limited to the specific methods, compounds, materials, manufacturing techniques, uses, and applications described herein, which can vary. It should also be understood that the terminology described herein is used only to describe particular embodiments and is not intended to limit the scope of this application. It must be noted that the singular forms “a,” “an,” and “the” used herein and in the appended claims include plural bases unless the context clearly indicates otherwise. Thus, for example, a reference to “a step” means a reference to one or more steps, and may include secondary steps. All conjunctions used should be understood in the broadest sense. Therefore, the word “or” should be understood to have the definition of logical “or” rather than logical “exclusive OR”, unless the context clearly indicates otherwise. Structures described herein will be understood to also refer to functional equivalents of that structure. Language that can be interpreted as approximate should be understood in that way, unless the context clearly indicates otherwise.

Claims

1. A light-emitting semiconductor device, characterized in that, From bottom to top, the structure comprises: a substrate, a first-type semiconductor layer, an active layer, and a second-type semiconductor layer; wherein, the second-type semiconductor layer comprises, from bottom to top, a second-type confinement layer, a second-type current spreading layer, a second buffer layer, a transition layer, a cutoff layer, and a second-type ohmic contact layer, and the second buffer layer is Al. j Ga k As x P y Layer, where 0.025≤j≤0.1, 0.4≤k≤0.475, 0.1≤x≤0.2, 0.3≤y≤0.4, and j+k=0.5, x+y=0.

5.

2. The light-emitting semiconductor device as described in claim 1, characterized in that, The second type current spreading layer and the second buffer layer both contain Al, Ga and As elements; the second buffer layer and the transition layer both contain Ga, As and P elements; the transition layer and the cutoff layer both contain Ga and P elements; and the cutoff layer and the second type ohmic contact layer both contain Ga and P elements.

3. The light-emitting semiconductor device as described in claim 1, characterized in that, The defect density of the stop layer is greater than that of the second type of ohmic contact layer.

4. The light-emitting semiconductor device as described in claim 1, characterized in that, The composition of Al and As elements in the second buffer layer gradually decreases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer, while the composition of Ga and P elements in the second buffer layer gradually increases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer.

5. The light-emitting semiconductor device as described in claim 4, characterized in that, The composition of the second buffer layer, which is in direct contact with the second type current spreading layer, is Al. 0.25 Ga 0.25 As 0.25 P 0.25 .

6. The light-emitting semiconductor device as described in claim 1, characterized in that, The lattice constant of the second buffer layer gradually decreases from the side closer to the second type current spreading layer to the side farther away from the second type current spreading layer.

7. The light-emitting semiconductor device as described in claim 1, characterized in that, The transition layer is Ga. 0.5 (As) m P 1-m ) 0.5 The layers are such that 0.05 < m < 0.

4.

8. The light-emitting semiconductor device as described in claim 1, characterized in that, The cutoff layer is a GaP layer.

9. The light-emitting semiconductor device as described in claim 1, characterized in that, The second type of current spreading layer is an AlGaAs layer, and the second type of ohmic contact layer is a GaP layer.

10. The light-emitting semiconductor device as claimed in claim 1, characterized in that, The composition of each element in the second buffer layer remains unchanged.

11. The light-emitting semiconductor device as claimed in claim 10, characterized in that, The second buffer layer is composed of Al 0.25 Ga 0.25 As 0.25 P 0.25 .

12. The light-emitting semiconductor device as claimed in claim 1, characterized in that, The thickness of the second buffer layer is 10nm~100nm.

13. The light-emitting semiconductor device as claimed in claim 1, characterized in that, The thickness of the transition layer is 10nm~50nm.

14. The light-emitting semiconductor device as claimed in claim 1, characterized in that, The thickness of the stop layer is 10nm~50nm.

15. The light-emitting semiconductor device as claimed in claim 1, characterized in that, The second buffer layer is doped with a type II dopant, which is at least one of magnesium and zinc.

16. The light-emitting semiconductor device as claimed in claim 15, characterized in that, The dopant types in the transition layer and the stop layer are the same as those in the second buffer layer.

17. The light-emitting semiconductor device as claimed in claim 1, characterized in that, The first type of semiconductor layer comprises, from bottom to top, a first type of ohmic contact layer, a first type of current spreading layer, and a first type of confinement layer.

18. The light-emitting semiconductor device as claimed in claim 1, characterized in that, The active layer, from bottom to top, includes: a first barrier layer, a multiple quantum well layer, and a second barrier layer.

19. The light-emitting semiconductor device as claimed in claim 18, characterized in that, The multiple quantum well layer is a periodic structure formed by alternating growth of well layers and barrier layers.

20. The light-emitting semiconductor device as claimed in claim 19, characterized in that, The number of periods in the multi-quantum well layer is 6 to 30.

21. The light-emitting semiconductor device as claimed in claim 1, characterized in that, It also includes a first buffer layer, which is located between the substrate and the first type of semiconductor layer.

22. A method for fabricating a light-emitting semiconductor device, characterized in that, include: Provide substrate; A first-type semiconductor layer and an active layer are sequentially grown on the substrate; A second type semiconductor layer is grown on the active layer; wherein, from bottom to top, the second type semiconductor layer includes a second type confinement layer, a second type current spreading layer, a second buffer layer, a transition layer, a cutoff layer, and a second type ohmic contact layer, and the second buffer layer is Al. j Ga k As x P y Layer, where 0.025≤j≤0.1, 0.4≤k≤0.475, 0.1≤x≤0.2, 0.3≤y≤0.4, and j+k=0.5, x+y=0.

5.

23. The preparation method according to claim 22, characterized in that, The second type current spreading layer and the second buffer layer both contain Al, Ga and As elements; the second buffer layer and the transition layer both contain Ga, As and P elements; the transition layer and the cutoff layer both contain Ga and P elements; and the cutoff layer and the second type ohmic contact layer both contain Ga and P elements.

24. The preparation method according to claim 22, characterized in that, The defect density of the stop layer is greater than that of the second type of ohmic contact layer.

25. The preparation method according to claim 23, characterized in that, The composition of Al and As elements in the second buffer layer gradually decreases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer, while the composition of Ga and P elements in the second buffer layer gradually increases from the side closer to the second type current spread layer to the side farther away from the second type current spread layer.

26. The preparation method according to claim 25, characterized in that, The composition of the second buffer layer, which is in direct contact with the second type current spreading layer, is Al. 0.25 Ga 0.25 As 0.25 P 0.25 .

27. The preparation method according to claim 25, characterized in that, The lattice constant of the second buffer layer gradually decreases from the side closer to the second type current spreading layer to the side farther away from the second type current spreading layer.

28. The preparation method according to claim 22, characterized in that, The transition layer is Ga. 0.5 (As) m P 1-m ) 0.5 The cutoff layer is a GaP layer, and 0.05 < m < 0.

4.

29. The preparation method according to claim 22, characterized in that, The second type of current spreading layer is an AlGaAs layer, and the second type of ohmic contact layer is a GaP layer.

30. The preparation method according to claim 24, characterized in that, The composition of each element in the second buffer layer remains unchanged.

31. The preparation method according to claim 22, characterized in that, The thickness of the second buffer layer is 10nm~100nm.

32. The preparation method according to claim 22, characterized in that, The thickness of the transition layer is 10nm~50nm.

33. The preparation method according to claim 22, characterized in that, The thickness of the stop layer is 10nm~50nm.

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