A novel long-wave infrared detector and its preparation method

Abstract

The present application discloses a novel long-wave infrared detector, which relates to the semiconductor field. The present application is a novel structure of a pπMp type antimonide type II superlattice infrared detector based on a planar structure, with an InAs / GaSb superlattice structure as a contact layer and an absorption layer, and an InAs / GaSb / AlSb / GaSb superlattice structure as a barrier layer, wherein the contact layer, the absorption layer and the barrier layer are all p-type regions. The present application screens the barrier layer material and optimizes each layer of the device, effectively suppressing the dark current level while ensuring quantum efficiency, thereby ensuring the working performance of the device. The present application contains a T2SL structural system that can be prepared using epitaxial growth tools such as molecular beam epitaxy and metal organic chemical deposition, and the preparation process is simple.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a novel long-wave infrared detector and a preparation method thereof. Background Art

[0002] Since the Second World War, the urgent demand for military equipment applications has greatly promoted the development of infrared detector technology. Infrared focal plane detectors play a key role in various military and civilian infrared imaging systems, such as night vision reconnaissance, strategic warning, target identification and tracking, medical diagnosis, weather forecast, etc. At present, mercury cadmium telluride detectors (HgCdTe, MCT) have developed into the fourth generation, and quantum well infrared detectors (QWIP) and type II superlattice (T2SL) infrared detectors are developing towards the fourth generation. With the need for rapid development of military technology and the popularization of civilian infrared equipment, high-performance infrared detection materials are the key to the development of high-performance infrared imaging systems. The antimonide T2SL material developed in recent years is based on mature III-V semiconductor material growth technology and device technology, avoiding the disadvantages of difficult growth and high cost of MCT materials, and has a series of advantages such as quantum efficiency and wide spectrum response close to HgCdTe detectors, becoming the most preferred material to replace HgCdTe and quantum well infrared detectors.

[0003] In infrared focal plane detection systems, the dark current level is one of the important parameters to measure device performance. In superlattice infrared detectors, the main dark current mechanisms include diffusion current, recombination current, direct tunneling current, and trap-assisted tunneling current. Finding an appropriate barrier layer structure material can effectively reduce the dark current level of the device and improve the detector performance. Summary of the invention

[0004] The purpose of this application is to overcome the above problems or at least partially solve or alleviate the above problems.

[0005] According to one aspect of the present application, a novel long-wave infrared detector is provided, which is a novel antimonide type II superlattice infrared detector structure, whose overall structure is a pπMp structure, including at least a contact layer, an absorption layer and a barrier layer, wherein an InAs / GaSb superlattice structure is used as the contact layer and the absorption layer, and an InAs / GaSb / AlSb / GaSb superlattice structure is used as the barrier layer, and the contact layer, the absorption layer and the barrier layer are all p-type regions.

[0006] Optionally, the InAs / GaSb materials in the contact layer and the absorption layer can effectively control the bandgap width by controlling the thickness of InAs and GaSb, so that the wavelength range can cover the long-wave range.

[0007] Optionally, the InAs / GaSb / AlSb / GaSb material in the barrier layer effectively controls its bandgap width by controlling the thickness of InAs, GaSb and AlSb, thereby ensuring that its bandgap is large enough to hinder the movement of majority carriers.

[0008] Optionally, an InAs / GaSb superlattice structure is used as a contact layer, and a certain external bias voltage is required to start the collection of minority carriers.

[0009] Optionally, the InAs / GaSb / AlSb / GaSb superlattice structure forms an M-type InAs / GaSb / AlSb / GaSb barrier structure by inserting an AlSb layer in the middle of a GaSb layer.

[0010] Optionally, the pπMp structures are all doped with Be element, wherein the absorption layer is weakly doped with a doping concentration of 1×10 16 cm -3 The contact layer is heavily doped, with a doping concentration of 1×10 18 cm -3 The barrier layer is between the absorption layer and the contact layer, and the doping concentration is 1×10 15 cm -3 .

[0011] Optionally, the novel long-wave infrared detector comprises a GaSb substrate, a GaSb buffer layer, an InAs / GaSb superlattice lower contact layer, an InAs / GaSb superlattice absorption layer, an InAs / GaSb / AlSb / GaSb M-type superlattice barrier layer and an InAs / GaSb superlattice upper contact layer sequentially distributed along a set direction.

[0012] According to another aspect of the present application, a method for preparing the novel long-wave infrared detector is provided, characterized in that the method is performed according to the following steps:

[0013] Step 100, growing a GaSb buffer layer on a GaSb substrate, and performing p-type doping;

[0014] Step 200, growing a super lattice structure on the buffer layer as a lower contact layer, p-type doping, the super lattice structure is 13MLInAs / 7MLGaSb;

[0015] Step 300, growing a super lattice structure on the lower contact layer as an absorption layer, p-type doping, the super lattice structure is 13MLInAs / 7ML GaSb;

[0016] Step 400, growing a super lattice structure as a barrier layer on the absorption layer, p-type doping, the super lattice structure is 6MLInAs / 3ML GaSb / 5ML AlSb / 3ML GaSb;

[0017] Step 500, growing a super lattice structure on the barrier layer as an upper contact layer, and doping it with p-type, wherein the super lattice structure is 13MLInAs / 7ML GaSb;

[0018] In step 600 , the electrodes are installed between the lower contact layer and the buffer layer, and above the upper contact layer.

[0019] Optionally, in step 100, a 200 nm GaSb buffer layer is grown on the GaSb substrate, with a doping concentration of 1×10 18 cm -3 ;

[0020] In step 200, a 500 nm superlattice structure is grown on the buffer layer as a lower contact layer, and the doping concentration is 1×10 18 cm -3 ;

[0021] In step 300, a 2400 nm superlattice structure is grown on the lower contact layer as an absorption layer, and the doping concentration is 1×10 16 cm -3 ;

[0022] In step 400, an 800 nm superlattice structure is grown on the absorption layer as a barrier layer, and the doping concentration is 1×10 15 cm -3 ;

[0023] In step 500, a 500 nm superlattice structure is grown on the barrier layer as an upper contact layer, and the doping concentration is 1×10 18 cm -3 .

[0024] The new long-wave infrared detector of the present application is a new structure of a pπMp type antimonide type II superlattice infrared detector based on a planar structure, with an InAs / GaSb superlattice structure as a contact layer and an absorption layer, and an InAs / GaSb / AlSb / GaSb superlattice structure as a barrier layer, wherein the contact layer, the absorption layer and the barrier layer are all p-type regions. The present application screens the barrier layer material and optimizes each layer of the device, effectively suppressing the dark current level while ensuring quantum efficiency, thereby ensuring the working performance of the device. The T2SL structural system of the present application can be prepared using epitaxial growth tools such as molecular beam epitaxy and metal organic chemical deposition, and the preparation process is simple.

[0025] Based on the detailed description of the specific embodiments of the present application in combination with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Hereinafter, some specific embodiments of the present application will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0027] Figure 1 is a schematic diagram of an epitaxial structure of a novel long-wave infrared detector according to an embodiment of the present application;

[0028] Figure 2 is a schematic performance band diagram of a novel long-wave infrared detector of the present application;

[0029] Figure 3 The dark current level and quantum efficiency diagram before and after optimization are shown when a bias voltage of -0.2V is applied to the lower contact layer of the present application at 77K.

[0030] Figure 1 The symbols in the table have the following meanings:

[0031] 1-InAs / GaSb superlattice upper contact layer;

[0032] 2-InAs / GaSb / AlSb / GaSb M-type superlattice barrier layer;

[0033] 3-InAs / GaSb superlattice absorption layer;

[0034] 4-InAs / GaSb superlattice lower contact layer;

[0035] 5-GaSb buffer layer;

[0036] 6-GaSb substrate. DETAILED DESCRIPTION

[0037] Figure 1 It is a schematic diagram of the epitaxial structure of a new type of long-wave infrared detector according to an embodiment of the present application.

[0038] See also Figure 1This embodiment provides a new type of long-wave infrared detector, which is a new type of antimonide type II superlattice infrared detector structure, and its overall structure is a pπMp structure, which at least includes a contact layer, an absorption layer and a barrier layer. Among them, the InAs / GaSb superlattice structure is used as the contact layer and the absorption layer, and the InAs / GaSb / AlSb / GaSb superlattice structure is used as the barrier layer, and the contact layer, the absorption layer and the barrier layer are all p-type regions.

[0039] For the barrier layer, an AlSb layer is inserted in the middle of the GaSb layer to form an M-type InAs / GaSb / AlSb / GaSb barrier structure, and the device performance is optimized by controlling the thickness of InAs, GaSb and AlSb. For the contact layers at both ends, p-type heavy doping is selected to ensure the minority carrier type.

[0040] More specifically, the InAs / GaSb materials in the contact layer and the absorption layer effectively control the bandgap width by controlling the thickness of InAs and GaSb, so that the wavelength range can cover the long-wave range.

[0041] More specifically, the InAs / GaSb / AlSb / GaSb material in the barrier layer effectively controls its bandgap width by controlling the thickness of InAs, GaSb and AlSb, ensuring that its bandgap is large enough to hinder the movement of majority carriers.

[0042] The novel long-wave infrared detector of the present application is a novel structure of a pπMp type antimonide type II superlattice infrared detector based on a planar structure. The present application screens the barrier layer material and optimizes the parameter levels such as doping and thickness of each layer of the device, effectively suppressing the dark current level while ensuring quantum efficiency, and ensuring the working performance of the device.

[0043] More specifically, the entire pπMp structure is doped with Be element, wherein the absorption layer is weakly doped with a doping concentration of 1×10 16 cm -3 The contact layer is heavily doped, with a doping concentration of 1×10 18 cm -3 The barrier layer is between the absorption layer and the contact layer, and the doping concentration is 1×10 15 cm -3 This application mainly screens and optimizes barrier layer materials to ensure that the selected barrier layer materials can form a large hole barrier in the valence band while the device has a high quantum efficiency.

[0044] In this embodiment, Figure 1As shown, the novel long-wave infrared detector includes a GaSb substrate 1, a GaSb buffer layer 2, an InAs / GaSb superlattice lower contact layer 3, an InAs / GaSb superlattice absorption layer 4, an InAs / GaSb / AlSb / GaSb M-type superlattice barrier layer 5 and an InAs / GaSb superlattice upper contact layer 6 which are sequentially distributed along a set direction.

[0045] Figure 2 It is a schematic performance band diagram of a novel long-wave infrared detector of the present application. Figure 2 It can be clearly seen that the barrier region forms a very high hole barrier in the valence band, which divides the upper contact layer and the absorption layer, and prevents most holes injected from the upper contact layer from diffusing into the absorption layer, thus avoiding its influence on the light excitation process of the absorption layer. At the same time, there is also a barrier in the conduction band of the barrier region, which is caused by the same type of doping in the absorption region and the barrier region. The difference in doping concentration between the two regions will affect the size of the conduction band barrier. Since the absorption layer and the upper contact layer are made of the same superlattice material, the existence of the conduction band barrier plays a certain role in hindering the dark current density under low bias conditions.

[0046] Although the dark current property is better under a lower bias voltage, the photogenerated carriers at this time cannot overcome the potential barrier and be collected by the electrode. This structure can only collect photogenerated carriers normally when the turn-on voltage is reached, which is related to the height of the conduction band barrier, so the barrier height should not be too high. The conduction band barrier height of the barrier layer material given in this application is about 0.2eV, so higher photogenerated carriers can be collected only under a bias of -0.2V, which greatly reduces the process requirements of the device. Therefore, when the InAs / GaSb superlattice structure is used as the contact layer in this embodiment, a certain external bias is required to start the collection of minority carriers.

[0047] Figure 3 The dark current level and quantum efficiency diagram before and after optimization are shown in the figure when a bias of -0.2V is applied to the lower contact layer of the present invention at 77K. Theoretical calculations show that the dark current density of the structure before optimization is 10 -3 ~10 -2 A / cm 2 , the quantum efficiency peak is less than 30%; after optimization, the dark current density of the structure can be maintained at 10 -5 A / cm 2 The peak quantum efficiency can reach 42%, ensuring higher quantum efficiency while maintaining a lower dark current level.

[0048] This embodiment also provides a method for preparing a new type of long-wave infrared detector. The T2SL structural system can be prepared using epitaxial growth tools such as molecular beam epitaxy and metal organic chemical deposition.

[0049] Below Figure 1 The preparation method of the new long-wave infrared detector shown in FIG. 1 is used as an example to illustrate: follow the steps below to

[0050] Step 100, growing a 200nm GaSb buffer layer 2 on a GaSb substrate 1, p-type doping, with a doping concentration of 1×10 18 cm -3 ;

[0051] Step 200, growing a 500nm superlattice structure on the buffer layer 2 as the lower contact layer 3, p-type doping, the doping concentration is 1×10 18 cm -3 , the superlattice structure is 13ML InAs / 7ML GaSb;

[0052] Step 300, growing a 2400nm superlattice structure on the lower contact layer 3 as an absorption layer 4, p-type doping, the doping concentration is 1×10 16 cm -3 , the superlattice structure is 13ML InAs / 7ML GaSb;

[0053] Step 400, growing an 800 nm superlattice structure on the absorption layer 4 as the barrier layer 5, p-type doping, the doping concentration is 1×10 15 cm -3 , the superlattice structure is 6ML InAs / 3ML GaSb / 5ML AlSb / 3ML GaSb;

[0054] Step 500, growing a 500nm superlattice structure on the barrier layer 5 as the upper contact layer 6, p-type doping, the doping concentration is 1×10 18 cm -3 , the superlattice structure is 13ML InAs / 7ML GaSb;

[0055] Step 600: The electrode includes a lower electrode and an upper electrode. The lower electrode may be installed between the lower contact layer 3 and the buffer layer 2, and the upper electrode is installed above the upper contact layer.

[0056] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by technicians in the field to which this application belongs.

[0057] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0058] In addition, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0059] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0060] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0061] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A new type of long-wave infrared detector, characterized in that: It is a new type of antimonide type II superlattice infrared detector structure, whose overall structure is a pπMp structure, which at least includes a contact layer, an absorption layer and a barrier layer, wherein an InAs / GaSb superlattice structure is used as the contact layer and the absorption layer, and an InAs / GaSb / AlSb / GaSb superlattice structure is used as the barrier layer, and the contact layer, the absorption layer and the barrier layer are all p-type regions; The pπMp structure includes a GaSb substrate, a GaSb buffer layer, an InAs / GaSb superlattice lower contact layer, an InAs / GaSb superlattice absorption layer, an InAs / GaSb / AlSb / GaSb M-type superlattice barrier layer and an InAs / GaSb superlattice upper contact layer which are sequentially distributed along a set direction.

2. The novel long-wave infrared detector according to claim 1 is characterized in that: The InAs / GaSb materials in the contact layer and the absorption layer can effectively control the bandgap width by controlling the thickness of InAs and GaSb, so that the wavelength range can cover the long-wave range.

3. The novel long-wave infrared detector according to claim 1 is characterized in that: The InAs / GaSb / AlSb / GaSb material in the barrier layer effectively controls its forbidden band width by controlling the thickness of InAs, GaSb and AlSb, thereby ensuring that its band gap is large enough to hinder the movement of majority carriers.

4. The novel long-wave infrared detector according to claim 1 is characterized in that: Using an InAs / GaSb superlattice structure as the contact layer requires a certain external bias to start collecting minority carriers.

5. The novel long-wave infrared detector according to claim 1 is characterized in that: The InAs / GaSb / AlSb / GaSb superlattice structure forms an M-type InAs / GaSb / AlSb / GaSb barrier structure by inserting an AlSb layer in the middle of a GaSb layer.

6. The novel long-wave infrared detector according to claim 1 is characterized in that: The pπMp structures are all doped with Be elements, wherein the absorption layer is weakly doped with a doping concentration of 1×10 16 cm -3 The contact layer is heavily doped, with a doping concentration of 1×10 18 cm -3 The barrier layer is between the absorption layer and the contact layer, and the doping concentration is 1×10 15 cm -3 .

7. A method for preparing the novel long-wave infrared detector according to claim 1, characterized in that: Follow the steps outlined below: Step 100, growing a GaSb buffer layer on a GaSb substrate, and performing p-type doping; Step 200, growing a super lattice structure on the buffer layer as a lower contact layer, p-type doping, the super lattice structure is 13MLInAs / 7MLGaSb; Step 300, growing a super lattice structure on the lower contact layer as an absorption layer, p-type doping, the super lattice structure is 13MLInAs / 7ML GaSb; Step 400, growing a super lattice structure as a barrier layer on the absorption layer, p-type doping, the super lattice structure is 6MLInAs / 3ML GaSb / 5ML AlSb / 3ML GaSb; Step 500, growing a super lattice structure on the barrier layer as an upper contact layer, and doping it with p-type, wherein the super lattice structure is 13MLInAs / 7ML GaSb; In step 600 , the electrodes are installed between the lower contact layer and the buffer layer, and above the upper contact layer.

8. The preparation method according to claim 7, characterized in that: In step 100, a 200 nm GaSb buffer layer is grown on a GaSb substrate with a doping concentration of 1×10 18 cm -3 ; In step 200, a 500 nm superlattice structure is grown on the buffer layer as a lower contact layer, and the doping concentration is 1×10 18 cm -3 ; In step 300, a 2400 nm superlattice structure is grown on the lower contact layer as an absorption layer, and the doping concentration is 1×10 16 cm -3 ; In step 400, an 800 nm superlattice structure is grown on the absorption layer as a barrier layer, and the doping concentration is 1×10 15 cm -3 ; In step 500, a 500 nm superlattice structure is grown on the barrier layer as an upper contact layer, and the doping concentration is 1×10 18 cm -3 .

Images