Semiconductor infrared avalanche detector and preparation method thereof

Abstract

The invention provides a semiconductor infrared avalanche detector. The semiconductor infrared avalanche detector comprises a substrate layer, a buffer layer, a multiplication layer, an absorption layer and a contact layer. The substrate layer is located at the bottommost layer of the detector. The buffer layer is over the substrate layer. The multiplication layer is over the buffer layer. The absorber layer is over the multiplication layer. The contact layer is located above the absorption layer and located on the topmost layer of the detector. The multiplication layer and the buffer layer are lattice-matched. The interior of the absorption layer is of a superlattice structure. The invention also comprises a method. According to the semiconductor infrared avalanche detector, the carrier ionization characteristic of the semiconductor infrared avalanche detector can be effectively regulated and controlled based on the antimony and bismuth-containing compound semiconductor multiplication layer and the superlattice absorption layer structure, the low-noise avalanche detector is achieved, and the semiconductor infrared avalanche detector is suitable for medium-wave infrared and long-wave infrared weak signal detection. According to the method, a conventional molecular beam epitaxy method is adopted for growth, the structure and the preparation operation process are simple and easy to control, and the method can be conveniently popularized to preparation of array type detector focal plane chips.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic materials and devices, and particularly to a semiconductor infrared avalanche detector and a preparation method thereof. Background Art

[0002] With the increasing demand for weak optical signal detection in many scientific and technological fields, the research on weak optical signal detection technology has attracted the attention of countries around the world and has become a hot topic in current international research. At present, the devices used to achieve weak optical signal detection mainly include photomultiplier tubes, avalanche photodiodes, superconducting single-photon detectors, etc. Photomultiplier tubes have high gain in the visible and ultraviolet bands and have been widely studied and applied. However, in the infrared communication band, their application is limited due to disadvantages such as mismatched response wavelength, high noise, and low quantum efficiency. Superconducting single-photon detectors have excellent performance but must operate at extremely low temperatures. In the infrared band, avalanche detectors have advantages such as high quantum efficiency, large response wavelength range, low operating voltage, and low power consumption, and thus have obtained rapid development.

[0003] Avalanche detectors have higher sensitivity and detectivity than ordinary PN detectors due to their internal multiplication effect, and are particularly suitable for the detection of weak optical signals, and have important applications in many fields such as quantum communication and lidar. Avalanche detectors with silicon as the absorption layer are commonly used in the visible light band. In the near-infrared band with a wavelength of about 1.1 microns or more, avalanche detectors mainly use III-V materials such as InGaAsP as the absorption layer. In the mid-wave infrared band, II-VI mercury cadmium telluride materials are mostly used as the absorption layer. Mercury cadmium telluride materials have lower excess noise due to their unique energy band structure and multiplication ionization characteristics. However, the preparation of mercury cadmium telluride materials is difficult and their stability is challenging. Antimonide type-II superlattice materials as the absorption layer can detect mid-wave and long-wave infrared signals, and their energy band structure is mainly affected by the thickness of the superlattice materials. The uniformity and stability of their material and device performance have attractive prospects.

[0004] In terms of the structure of avalanche detectors, the early structures only adopted a simple PIN structure, operating at a relatively high reverse voltage. However, the excessively high operating voltage made the homojunction devices have significant noise. For traditional near-infrared InGaAs avalanche detectors, a heterostructure with a separated absorption region and gain region was later developed. An InP multiplication region with a relatively wider bandgap was added outside the absorption region to form a structure with a separated absorption region and multiplication region. A transition layer was also introduced between the narrow-bandgap InGaAs absorption region and the wide-bandgap InP multiplication region to reduce the accumulation effect of energy band spikes on carriers, forming a structure with a separated absorption region and multiplication region and having a transition layer. Or by introducing a charge region, a so-called structure with a separated absorption region, charge region, and multiplication region and having a transition layer was formed. For avalanche detectors in other wavelength bands or with other absorption layers, relatively less research has been conducted on their structures.

[0005] An important performance parameter of semiconductor infrared avalanche detectors is noise. In the relatively mainstream avalanche detector structure with a separated absorption region and multiplication region, the main component of the device noise is excess noise, which is mainly affected by the ratio of the electron and hole ionization coefficients of the multiplication region material. The ionization coefficient characteristics of semiconductor materials are most mainly affected by the intrinsic characteristic parameters of the materials. For mid- and far-infrared semiconductor avalanche detectors using InAs / GaSb or InAs / InAsSb superlattices as the optical absorption layer, InAs / GaSb, InAs / AlSb, or InAs / InAsSb and other superlattice materials are still generally used as the multiplication layer at present. This is mainly because it is relatively convenient to adjust and match the lattice with the absorption layer material, so materials of the same type and system as the absorption layer are used. However, the ratio of the electron and hole ionization coefficients of such materials is relatively large, indicating that the electron ionization coefficient and the hole ionization coefficient are relatively close, thus causing relatively large noise in semiconductor infrared avalanche detectors. Therefore, there is an urgent need to develop new infrared avalanche detector structures. Summary of the Invention

[0006] The purpose of the present invention is to provide a semiconductor infrared avalanche detector and its manufacturing method, mainly to solve the problems existing in the above-mentioned prior art, and it can overcome the defects of high noise and limited regulation in mid- and far-infrared avalanche detectors in the prior art.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is to provide a semiconductor infrared avalanche detector, characterized in that it includes a substrate layer, a buffer layer, a multiplication layer, an absorption layer, and a contact layer; the substrate layer is located at the bottommost layer of the detector; the buffer layer is located above the substrate layer; the multiplication layer is located above the buffer layer; the absorption layer is located above the multiplication layer; the contact layer is located above the absorption layer and at the topmost layer of the detector; the multiplication layer is lattice-matched with the buffer layer; the inside of the absorption layer is a superlattice structure.

[0008] Further, the material of the substrate layer is GaSb or InAs.

[0009] Further, when the material of the substrate layer is GaSb, the material of the buffer layer is N-type GaSb; when the material of the substrate layer is InAs, the material of the buffer layer is N-type InAs; the thickness of the buffer layer is 1 to 2 micrometers, and the electron concentration is 1×10 18 cm -3 to 5×10 18 cm -3 .

[0010] Further, the material of the multiplication layer is AlGaAsSbBi or AlGaPSbBi, and the thickness is 0.3 to 2 micrometers; the multiplication layer is not doped and lattice-matched with the GaSb or InAs of the buffer layer.

[0011] Further, when the material of the substrate layer is GaSb, the material of the contact layer is P-type GaSb; when the material of the substrate layer is InAs, the material of the contact layer is P-type InAs; the thickness of the contact layer is 0.3 to 1 micrometer, and the hole concentration is 1×10 18 cm -3 to 8×10 18 cm -3 .

[0012] Further, the absorption layer is composed of InAs and GaSb, or forms a superlattice structure composed of InAs and InAsSb; the absorption layer is not doped.

[0013] Further, when the absorption layer forms a superlattice structure composed of InAs and GaSb, in each superlattice period, the thickness of InAs is 11 to 16 atomic layers, and the thickness of GaSb is 5 to 8 atomic layers; when the absorption layer forms a superlattice structure composed of InAs and InAsSb, in each superlattice period, the thickness of InAs is 11 to 14 atomic layers, and the thickness of InAsSb is 4 to 7 atomic layers.

[0014] Further, an N electrode is disposed on the buffer layer; a P electrode is disposed on the contact layer; the N electrode and the P electrode are used for external electrical connection of the detector.

[0015] The present invention also discloses a preparation method for manufacturing the above semiconductor infrared avalanche detector, which is characterized by including the steps of:

[0016] Step S100, preprocessing the substrate layer;

[0017] Step S200: Grow the buffer layer made of the same material as the substrate layer on the substrate layer.

[0018] Step S300: Grow the multiplication layer lattice-matched to the buffer layer on the buffer layer.

[0019] Step S400: Grow the absorption layer on the multiplication layer.

[0020] Step S500: Grow the contact layer on the absorption layer.

[0021] Step S600: Position the photosensitive surface of the detector using photolithography.

[0022] Step S700: Use an etching process to etch away the contact layer, the absorption layer, and the multiplication layer in the area outside the photosensitive surface of the detector to form a detector structure.

[0023] Step S800: Generate an N electrode and a P electrode on the buffer layer and the contact layer respectively; the N electrode is connected to the buffer layer, and the P electrode is connected to the contact layer.

[0024] Furthermore, in step S800, it also includes:

[0025] Step S801: Deposit a passivation film on the buffer layer and the contact layer.

[0026] Step S802: Use photolithography to form an N electrode region and a P electrode region on the buffer layer and the contact layer.

[0027] Step S803: Etch away the passivation film on the N electrode region and the P electrode region.

[0028] Step S804: Grow an N-type ohmic contact metal on the N electrode region to form an N electrode; grow a P-type ohmic contact metal on the P electrode region to form a P electrode.

[0029] In view of the above technical features, the semiconductor infrared avalanche detector and its manufacturing method of the present invention have the following advantages compared with the prior art:

[0030] 1. The semiconductor infrared avalanche detector of the present invention, based on the compound semiconductor multiplication layer containing antimony and bismuth and the superlattice absorption layer structure, can effectively regulate the carrier ionization characteristics of the semiconductor infrared avalanche detector, realize an avalanche detector with low noise, and is suitable for detecting weak signals in mid-wave infrared and long-wave infrared.

[0031] 2. The preparation method of the semiconductor infrared avalanche detector of the present invention uses the conventional molecular beam epitaxy method for growth. The structure and preparation operation process are simple, easy to control, and can be conveniently extended to the preparation of the focal plane chip of the array-type avalanche detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of the semiconductor infrared avalanche detector of the present invention;

[0033] Figure 2 is a schematic structural diagram of a preferred embodiment of the semiconductor infrared avalanche detector of the present invention;

[0034] Figure 3 is a schematic structural diagram of another preferred embodiment of the semiconductor infrared avalanche detector of the present invention;

[0035] Figure 4 is a flowchart of the method for preparing the semiconductor infrared avalanche detector of the present invention.

[0036] In the figure: 1 - substrate layer, 2 - buffer layer, 3 - multiplication layer, 4 - absorption layer, 5 - contact layer, 6 - N electrode, 7 - P electrode, 8 - passivation film. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The present invention will be further described below in conjunction with the specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0038] Please refer to Figures 1 to 3 , the present invention discloses a semiconductor infrared avalanche detector. As shown in the figure, a preferred embodiment thereof includes a substrate layer 1, a buffer layer 2, a multiplication layer 3, an absorption layer 4, and a contact layer 5. The substrate layer 1 is located at the bottom layer of the detector. Above the substrate layer 1 is the buffer layer 2. And the multiplication layer 3 is located above the buffer layer 2. The lattice of the multiplication layer 3 matches that of the buffer layer 2. Above the multiplication layer 3 is the absorption layer 4. The absorption layer 4 has a superlattice structure inside. The contact layer 5 is located above the absorption layer 4 and is at the top layer of the detector.

[0039] The material of the substrate layer 1 can be selected as GaSb or InAs. The material of the buffer layer 2 matches that of the substrate layer 1, that is, when the material of the substrate layer 1 is GaSb, the material of the buffer layer 2 is N-type GaSb. Similarly, when the material of the substrate layer 1 is InAs, the material of the buffer layer is N-type InAs. The thickness of the buffer layer is preferably 1 to 2 micrometers according to different requirements, and its electron concentration is 1×10 18 cm -3to 5×10 18 cm -3 。A passivation film 8 is covered on the buffer layer 2. The N electrode 6 passes through the passivation film 8 and is connected to the buffer layer 2, serving as an external electrical connection point of the detector.

[0040] There are also two choices for the material of the multiplication layer 3 above the buffer layer 2, namely Al GaAsSbBi or AlGaPSbBi, and the thickness is preferably 0.3 micrometers to 2 micrometers. The multiplication layer 3 is not doped, and its lattice structure matches that of GaSb or InAs constituting the buffer layer 2.

[0041] Above the multiplication layer 3 is the absorption layer 4, which has a superlattice structure. The superlattice structure is composed of two materials, which can be selected from InAs and GaSb, or from InAs and InAsSb. The absorption layer 4 is not doped. The microstructure of the superlattice structures composed of different materials is slightly different. However, there is a certain relationship between the thicknesses of the two materials. Specifically, when the absorption layer 4 has a superlattice structure composed of InAs and GaSb, in each superlattice period, the thickness of InAs is preferably 11 to 16 atomic layers, and the thickness of GaSb is preferably 5 to 8 atomic layers. When the absorption layer 4 has a superlattice structure composed of InAs and InAsSb, in each superlattice period, the thickness of InAs is preferably 11 to 14 atomic layers, and the thickness of InAsSb is preferably 4 to 7 atomic layers.

[0042] Above the absorption layer 4 is the contact layer 5. Similar to the buffer layer 2, the material of the contact layer 5 is related to the material of the substrate layer 1. Specifically, when the material of the substrate layer 1 is GaSb, the material of the contact layer 5 is selected as P-type GaSb. When the material of the substrate layer 1 is InAs, the material of the contact layer 5 is selected as P-type InAs. The thickness of the contact layer 5 is preferably 0.3 micrometers to 1 micrometer, and the hole concentration is 1×10 18 cm -3 to 8×10 18 cm -3 。A passivation film 8 is covered on the contact layer 5. The P electrode 7 passes through the passivation film 8 and is connected to the contact layer 5, serving as another external electrical connection point of the detector. The N electrode 6 and the P electrode 7 match to form a complete external electrical connection of the detector.

[0043] Please refer to Figure 2 In this embodiment, it is selected to start manufacturing the detector on a 3-inch GaSb substrate, that is, the material of the substrate layer 1 is GaSb. On the substrate layer 1, there is a 1-micrometer-thick N-type GaSb buffer layer 2, doped with an electron concentration of 2×10 18 cm -3。On the buffer layer 2, an N electrode 6 is provided. The material of the multiplication layer 3 is undoped Al GaAsSbBi, lattice-matched to the GaSb of the buffer layer 2 below it, with a thickness of 0.5 micrometers. The absorption layer 4 located above the multiplication layer 3 has a thickness of 3 micrometers and is composed of undoped InAs and InAsSb to form a superlattice structure. The thicknesses of InAs and InAsSb in each superlattice period are 13 and 5 atomic layers respectively. The top layer is a 0.5-micrometer-thick P-type GaSb contact layer 5, doped with a hole concentration of 1×10 18 cm -3 。On the contact layer 5, a P electrode 7 is provided.

[0044] Please refer to Figure 3 。In another embodiment, it is selected to start manufacturing the detector on a 2-inch InAs substrate, that is, the material of the substrate layer 1 is InAs. On the substrate layer 1, there is a 1.5-micrometer-thick N-type InAs buffer layer 2, doped with an electron concentration of 1×10 18 cm -3 。On the buffer layer 2, an N electrode 6 is provided. The material of the multiplication layer 3 is undoped Al GaPSbBi, lattice-matched to the InAs of the buffer layer 2 below it, with a thickness of 1 micrometer. The absorption layer 4 located above the multiplication layer 3 has a thickness of 2.5 micrometers and is composed of undoped InAs and GaSb to form a superlattice structure. The thicknesses of InAs and GaSb in each superlattice period are 15 and 7 atomic layers respectively. The top layer is a 0.3-micrometer-thick P-type InAs contact layer 5, doped with a hole concentration of 2×10 18 cm -3 。On the contact layer 5, a P electrode 7 is provided.

[0045] Please refer to Figure 4 。The present invention also discloses a preparation method for manufacturing the above semiconductor infrared avalanche detector. A preferred embodiment thereof includes the steps:

[0046] Step S1, preprocess the substrate layer.

[0047] Place the substrate material in the growth chamber of the molecular beam epitaxy chamber, and process the substrate layer through stepwise heating and reflection high-energy electron diffraction to deoxidize it.

[0048] Step S2, grow the buffer layer.

[0049] After deoxidation is completed, adjust the temperature of the substrate layer to the growth temperature, and then use the molecular epitaxy process to grow the buffer layer while completing electron doping.

[0050] Step S3, grow the multiplication layer.

[0051] Use the molecular epitaxy process to grow a multiplication layer lattice-matched to the buffer layer.

[0052] Step S4, grow the absorption layer.

[0053] Using molecular epitaxy process, grow an absorption layer with a superlattice structure. In each superlattice period, the thickness of different materials is constant.

[0054] Step S5, grow the contact layer.

[0055] Using molecular epitaxy process, grow the contact layer and simultaneously complete hole doping.

[0056] Step S6, use photolithography to position the photosensitive surface of the detector.

[0057] Coat a photoresist on the surface of the epitaxial material and pattern the photolithography mesa.

[0058] Step S7, form the detector structure

[0059] Use an etching process (such as wet etching) to etch away the contact layer, absorption layer, and multiplication layer in the area outside the photosensitive surface of the detector until the buffer layer is exposed, thereby forming a detector mesa structure.

[0060] Step S8, deposit a passivation film.

[0061] Remove the photoresist and deposit a SiN passivation film on the buffer layer and the contact layer using inductively coupled plasma chemical vapor deposition.

[0062] Step S9, photolithograph the electrode area.

[0063] Photolithographically form an N electrode area and a P electrode area on the buffer layer and the contact layer respectively.

[0064] Step S10, remove the passivation film.

[0065] Use plasma etching to remove the SiN x passivation film on the N electrode area and the P electrode area.

[0066] Step S11, grow the electrodes.

[0067] Using electron beam evaporation process, grow an N-type ohmic contact metal on the N electrode area and a P-type ohmic contact metal on the P electrode area. Then strip off the metal in the areas other than the electrode areas, leaving only the metal in the N electrode area and the P electrode area, thereby forming an N electrode in the N electrode area and a P electrode in the P electrode area. Strip off the metal in the areas other than the electrode areas, leaving only the metal in the electrode areas.

[0068] The above are only the preferred embodiments of the present invention, and do not thereby limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall similarly be included within the patent protection scope of the present invention.

Claims

1. A semiconductor infrared avalanche detector, characterized in that: The detector comprises a substrate layer, a buffer layer, a multiplication layer, an absorption layer and a contact layer; the substrate layer is located at the bottom layer of the detector; the buffer layer is located above the substrate layer; the multiplication layer is located above the buffer layer; the absorption layer is located above the multiplication layer; the contact layer is located above the absorption layer and is at the top layer of the detector; the multiplication layer is lattice matched with the buffer layer; the absorption layer has a superlattice structure inside.

2. The semiconductor infrared avalanche detector according to claim 1, characterized in that: The material of the substrate layer is GaSb or InAs.

3. The semiconductor infrared avalanche detector according to claim 2, characterized in that: When the material of the substrate layer is GaSb, the material of the buffer layer is N-type GaSb; when the material of the substrate layer is InAs, the material of the buffer layer is N-type InAs; the thickness of the buffer layer is 1 micron to 2 microns, and the electron concentration is 1×10 18 cm -3 Up to 5×10 18 cm -3 .

4. The semiconductor infrared avalanche detector according to claim 2, characterized in that: The multiplication layer is made of AlGaAsSbBi or AlGaPSbBi, with a thickness of 0.3 micrometers to 2 micrometers; the multiplication layer is undoped and lattice-matched with GaSb or InAs of the buffer layer.

5. The semiconductor infrared avalanche detector according to claim 2, characterized in that: When the material of the substrate layer is GaSb, the material of the contact layer is P-type GaSb; when the material of the substrate layer is InAs, the material of the contact layer is P-type InAs; the thickness of the contact layer is 0.3 micrometer to 1 micrometer, and the hole concentration is 1×10 18 cm -3 Up to 8×10 18 cm -3 .

6. The semiconductor infrared avalanche detector according to claim 1, characterized in that: The absorption layer is composed of InAs and GaSb, or InAs and InAsSb to form a super lattice structure; the absorption layer is undoped.

7. The semiconductor infrared avalanche detector according to claim 6, characterized in that: When the absorption layer is composed of InAs and GaSb to form a superlattice structure, in each superlattice period, the thickness of InAs is 11 to 16 atomic layers, and the thickness of GaSb is 5 to 8 atomic layers; when the absorption layer is composed of InAs and InAsSb to form a superlattice structure, in each superlattice period, the thickness of InAs is 11 to 14 atomic layers, and the thickness of InAsSb is 4 to and 7 atomic layers.

8. The semiconductor infrared avalanche detector according to claim 1, characterized in that: An N electrode is arranged on the buffer layer; a P electrode is arranged on the contact layer; and the N electrode and the P electrode are used for external electrical connection of the detector.

9. A method for manufacturing the semiconductor infrared avalanche detector according to claim 1, characterized in that: Contains steps: Step S100, pre-treating the substrate layer; Step S200, growing the buffer layer made of the same material as the substrate layer on the substrate layer; Step S300, growing the multiplication layer lattice-matched with the buffer layer on the buffer layer; Step S400, growing the absorption layer on the multiplication layer; Step S500, growing the contact layer on the absorption layer; Step S600, positioning the photosensitive surface of the detector by photolithography; Step S700, using an etching process to etch away the contact layer, the absorption layer and the multiplication layer in the area outside the photosensitive surface of the detector to form a detector structure; Step S800: Generating an N electrode and a P electrode on the buffer layer and the contact layer, respectively; the N electrode is connected to the buffer layer, and the P electrode is connected to the contact layer.

10. The method for preparing a semiconductor infrared avalanche detector according to claim 9, characterized in that: In step S800, it also includes: Step S801, depositing a passivation film on the buffer layer and the contact layer; Step S802, photolithographically forming an N-electrode region and a P-electrode region on the buffer layer and the contact layer; Step S803, etching and removing the passivation film on the N-electrode region and the P-electrode region; Step S804, growing an N-type ohmic contact metal on the N-electrode region to form an N-electrode; A P-type ohmic contact metal is grown on the P-electrode region to form a P-electrode.

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