Photodetector and method of manufacturing the same
By employing an In composition-gradient buffer layer and an AlGaAsSb electronic barrier layer in an InGaAs-based photodetector, the dislocation density problem caused by lattice mismatch was solved, enabling effective detection of near-infrared extended wavelengths and improving photoresponse characteristics.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI
- Filing Date
- 2023-03-17
- Publication Date
- 2026-05-12
AI Technical Summary
When existing InGaAs-based photodetectors detect near-infrared extended wavelengths (2–3 μm), the increased In content leads to lattice mismatch, resulting in a larger dislocation density. This affects the crystal quality of the absorption layer and the transport efficiency of photogenerated carriers, leading to a decrease in dark current and photoresponse characteristics.
InxAl1-xAs with gradually varying In composition is used as the first buffer layer, combined with multiple sets of periodically alternating InyAl1-yAs and InyGa1-yAs layers as the second buffer layer, and AlGaAsSb is used as the electronic barrier layer to reduce dislocation density and improve crystal quality and photogenerated carrier transport efficiency.
It effectively reduced dislocation density, improved the crystal quality of the absorption layer, enhanced the detection capability of short-wave infrared extended wavelengths, reduced dark current, and improved the photoresponse characteristics of the device.
Smart Images
Figure CN116314394B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the technical fields of photodetector research and optoelectronic materials, and in particular to a photodetector and its fabrication method. Background Technology
[0002] The near-infrared extended band (2–3 μm) encompasses the absorption windows of various atmospheric gases, making it significant for diverse applications including gas detection, space remote sensing, and imaging. Detectors based on InGaAs as the absorption layer possess advantages such as high material absorption coefficient, high quantum efficiency, good room-temperature performance, and low noise. However, the InGaAs substrate needs to be matched with the InP substrate… 0.53 Ga 0.47 As materials have a cutoff response wavelength of only about 1.7 μm, making it impossible to effectively detect short-wave infrared extended wavelength bands.
[0003] By improving In x Ga 1-x The proportion of In component x in As enables InGaAs-based photodetectors to detect in the near-infrared extended wavelength range (2–3 μm). However, increasing the In component inevitably leads to a larger lattice mismatch between the absorption layer and the substrate, resulting in a larger dislocation density during growth. This leads to an increase in defects in the absorption layer and lower transport and collection efficiency of photogenerated carriers under operating conditions, affecting the dark current characteristics and photoresponse characteristics of the final device. Summary of the Invention
[0004] In view of the above problems, this disclosure provides a photodetector and its fabrication method to improve the problem of dislocation density caused by lattice mismatch.
[0005] One aspect of this disclosure provides a photodetector, comprising: a substrate, a first buffer layer, a second buffer layer, a first ohmic contact layer, an absorption layer, an electron barrier layer, and a second ohmic contact layer sequentially stacked on the substrate; wherein the first buffer layer is made of In with an In composition gradient. x Al 1-x As composition; the second buffer layer is composed of multiple sets of periodically alternating In layers grown in stacked layers. y Al 1-y As layer and In y Ga 1-y The structure consists of an As layer; the electron barrier layer is made of AlGaAsSb.
[0006] According to an embodiment of this disclosure, the In composition of the first buffer layer increases sequentially along the direction of the second buffer layer toward the substrate, and the In composition of the first buffer layer increases from 0.53 to 0.8, i.e. 0.53 < x ≤ 0.8.
[0007] According to an embodiment of this disclosure, the thickness of the first buffer layer is 30–50 nm; the doping source of the first buffer layer is Te, and the doping concentration is 1 × 10⁻⁶. 16 cm -3 ~1×10 17 cm -3 .
[0008] According to an embodiment of this disclosure, the second buffer layer is grown using 30 sets of periodically alternating In layers. y Al 1-y As layer and In y Ga 1-y As layer composition, 0.75≤y≤0.85; where In V Al 1-y As layer and In y Ga 1-y The thickness of the As layers is 10–15 nm, and the total thickness of the second buffer layer is 600–900 nm; the doping source of the second buffer layer is Te, and the doping concentration is 5 × 10⁻⁶. 16 cm -3 ~1×10 17 cm -3 .
[0009] According to an embodiment of this disclosure, the first ohmic contact layer uses In 0.8 Al 0.2 The first ohmic contact layer is made of As, with a thickness of 150–200 nm; the doping source for the first ohmic contact layer is Te, with a doping concentration of 5 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
[0010] According to embodiments of this disclosure, the absorber layer uses In 0.8 Ga 0.2 The absorber layer is made of As and has a thickness of 2–2.5 μm; the absorber layer is unintentionally doped.
[0011] According to embodiments of this disclosure, the thickness of the electron barrier layer is 50–100 nm; the electron barrier layer is unintentionally doped.
[0012] According to an embodiment of this disclosure, the second ohmic contact layer uses In 0.8 Al 0.2 The second ohmic contact layer is made of As, with a thickness of 150–200 nm; the doping source of the second ohmic contact layer is Te or Be, with a doping concentration of 1 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
[0013] According to an embodiment of this disclosure, the substrate is made of GaSb; the thickness of the substrate is 50 μm.
[0014] This disclosure also discloses a method for fabricating a photodetector, comprising: sequentially stacking a first buffer layer, a second buffer layer, a first ohmic contact layer, an absorption layer, an electron barrier layer, and a second ohmic contact layer on a substrate; wherein the first buffer layer is made of In with a graded In composition. x Al 1-x As composition; the second buffer layer is composed of multiple sets of periodically alternating In layers grown in stacked layers. y Al 1-y As layer and In y Ga 1-y Composed of As layers.
[0015] The at least one technical solution adopted in the embodiments of this disclosure has at least the following beneficial effects: This disclosure adopts In 0.8 Ga 0.2 As an absorption layer, As can be used to achieve effective detection in the extended short-wave infrared wavelength band; this disclosure uses In with gradually varying In composition. x Al 1-x As, and In y Al 1-y As layer and In y Ga 1-y The buffer layer prepared with As reduces the dislocation density caused by the large lattice mismatch between the high In content absorption layer and the substrate, reduces defects in the absorption layer, and improves the crystal quality of the absorption layer; this disclosure adopts the same method as In 0.8 Ga 0.2 As lattice-matched AlGaAsSb, as an electronic barrier layer, effectively improves the transport and collection efficiency of photogenerated carriers, reduces the recombination current generated by the depletion region, and thus reduces the dark current of the device. Attached Figure Description
[0016] To gain a more complete understanding of this disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, wherein:
[0017] Figure 1 A schematic diagram of the overall structure of the photodetector provided in an embodiment of this disclosure is shown.
[0018] [Explanation of Labels in the Attached Image]
[0019] 1. Substrate; 2. First buffer layer; 3. Second buffer layer; 4. First ohmic contact layer; 5. Absorption layer; 6. Electron barrier layer; 7. Second ohmic contact layer. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.
[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.
[0022] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.
[0023] In the description of this disclosure, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the subsystem or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.
[0024] Throughout the accompanying drawings, identical elements are represented by the same or similar reference numerals. Conventional structures or constructions have been omitted where they may cause confusion in understanding this disclosure. Furthermore, the shapes, dimensions, and positional relationships of the components in the drawings do not reflect actual size, scale, or actual positional relationships. Additionally, any reference numerals placed between parentheses in the claims should not be construed as limiting the claims.
[0025] Similarly, to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present disclosure. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0027] The near-infrared extended band (2–3 μm) encompasses the absorption windows of various atmospheric gases, making it significant for diverse applications including gas detection, space remote sensing, and imaging. Detectors based on InGaAs as the absorption layer possess advantages such as high material absorption coefficient, high quantum efficiency, good room-temperature performance, and low noise. However, the InGaAs substrate needs to be matched with the InP substrate… 0.53 Ga 0.47 As materials have a cutoff response wavelength of only about 1.7 μm, making it impossible to effectively detect short-wave infrared extended wavelength bands.
[0028] By improving In x Ga 1-x The proportion of In component x in As enables InGaAs-based photodetectors to detect in the near-infrared extended wavelength range (2–3 μm). However, increasing the In component inevitably leads to a larger lattice mismatch between the absorption layer and the substrate, resulting in a larger dislocation density during growth. This leads to an increase in defects in the absorption layer and lower transport and collection efficiency of photogenerated carriers under operating conditions, affecting the dark current characteristics and photoresponse characteristics of the final device.
[0029] To address the aforementioned problems, this disclosure provides a photodetector. Figure 1 A schematic diagram illustrating the overall structure of a photodetector provided in an embodiment of this disclosure is shown. The photodetector includes:
[0030] Please see Figure 1One aspect of this disclosure provides a photodetector, comprising: a substrate 1, a first buffer layer 2, a second buffer layer 3, a first ohmic contact layer 4, an absorption layer 5, an electron barrier layer 6, and a second ohmic contact layer 7 sequentially stacked on the substrate; wherein the first buffer layer 2 is made of In with a graded In composition. x Al 1-x As composition; the second buffer layer 3 is composed of multiple sets of periodically alternating In layers grown in stacked layers. y Al 1-y As layer and In y Ga 1-y The As layer is composed of an electron barrier layer 6 made of AlGaAsSb.
[0031] The In composition of the first buffer layer 2 increases sequentially along the direction of the second buffer layer 3 towards the substrate, from 0.53 to 0.8, i.e., 0.53 < x ≤ 0.8. In this embodiment of the present disclosure, the In composition increases linearly. In some other embodiments of the present disclosure, the In composition may also increase in other ways, which are not limited here.
[0032] The thickness of the first buffer layer 2 is 30–50 nm; the doping source of the first buffer layer 2 is Te, and the doping concentration is 1 × 10⁻⁶. 16 cm -3 ~1×10 17 cm -3 .
[0033] The second buffer layer 3 is grown using 30 sets of periodically alternating In layers. y Al 1-y As layer and In y Ga 1-y As layer composition, 0.75≤y≤0.85; where In y Al 1-y As layer and In y Ga 1-y The thickness of the As layers is 10–15 nm, and the total thickness of the second buffer layer 3 is 600–900 nm; the doping source of the second buffer layer 3 is re, and the doping concentration is 5 × 10⁻⁶. 16 cm -3 ~1×10 17 cm -3 .
[0034] In this embodiment of the disclosure, In with a gradual change in In composition is used. x Al 1-x As layer serves as the first buffer layer 2, and In layer is used. y Al 1-y As layer and In y Ga 1-yThe alternating As layers form a second buffer layer 3, which reduces the dislocation density caused by the large lattice mismatch between the high In content absorption layer and the substrate, reduces defects in the absorption layer, and improves the crystal quality of the absorption layer.
[0035] The first ohmic contact layer 4 uses In 0.8 Al 0.2 The first ohmic contact layer 4 is made of As and has a thickness of 150–200 nm; the doping source of the first ohmic contact layer 4 is Te, and the doping concentration is 5 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
[0036] Absorber layer 5 uses In 0.8 Ga 0.2 The absorber layer 5 is made of As and has a thickness of 2–2.5 μm; the absorber layer 5 is unintentionally doped. The electron barrier layer 6 uses AlGaAsSb material, and the absorber layer 5 uses In... 0.8 Ga 0.2 As material lattice matching effectively improves the transport and collection efficiency of photogenerated carriers, reduces the recombination current generated by the depletion region, and thus reduces the dark current of the device.
[0037] Meanwhile, in this embodiment of the disclosure, In is used 0.8 Ga 0.2 As, serving as the absorption layer 5, enables effective detection of the extended short-wave infrared wavelength band.
[0038] The thickness of the electron barrier layer 6 is 50–100 nm; the electron barrier layer 6 is unintentionally doped.
[0039] The second ohmic contact layer 7 uses In 0.8 Al 0.2 The second ohmic contact layer 7 is made of As and has a thickness of 150–200 nm; the doping source of the second ohmic contact layer 7 is Te or Be, and the doping concentration is 1 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
[0040] Substrate 1 is made of GaSb; the thickness of substrate 1 is 50 μm.
[0041] In the embodiments of this disclosure, the first buffer layer 2, the second buffer layer 3, the first ohmic contact layer 4, the absorption layer 5, the electronic barrier layer 6, and the second ohmic contact layer 7 are all grown using molecular beam epitaxy. Other growth methods may also be used in some other embodiments of this disclosure, and are not limited thereto.
[0042] Based on the same inventive concept, another aspect of this disclosure provides a method for fabricating a photodetector, comprising: sequentially stacking a first buffer layer 2, a second buffer layer 3, a first ohmic contact layer 4, an absorption layer 5, an electron barrier layer 6, and a second ohmic contact layer 7 on a substrate; wherein the first buffer layer 2 is made of In with a graded In composition. x Al 1-x As composition; the second buffer layer 3 is composed of multiple sets of periodically alternating In layers grown in stacked layers. y Al 1-y As layer and In y Ga 1-y The As layer is composed of an electron barrier layer 6 made of AlGaAsSb.
[0043] It should be noted that the embodiments of the preparation method of the photodetector correspond to the embodiments of the photodetector. The specific implementation details and the resulting technical effects are similar or the same as those in the embodiments of the photodetector, and will not be repeated here.
[0044] The specific embodiments described above provide a further detailed explanation of the technical solutions of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.
Claims
1. A photodetector, characterized in that, include: Substrate (1), a first buffer layer (2), a second buffer layer (3), a first ohmic contact layer (4), an absorption layer (5), an electronic barrier layer (6) and a second ohmic contact layer (7) are sequentially stacked on the substrate (1). The first buffer layer (2) uses In with a gradually changing In composition. x Al 1-x As composition; the second buffer layer (3) adopts multiple sets of periodically alternating stacked In y Al 1-y As layer and In y Ga 1-y The As layer is composed of an electron barrier layer (6) made of AlGaAsSb. The In composition of the first buffer layer (2) increases sequentially along the direction from the second buffer layer (3) toward the substrate (1), with the In composition of the first buffer layer (2) increasing from 0.53 to 0.8, i.e., 0.
53. <x≤0.8; The thickness of the first buffer layer (2) is 30~50nm; the doping source of the first buffer layer (2) is Te, and the doping concentration is 1×10⁻⁶. 16 cm -3 ~1×10 17 cm -3 ; The second buffer layer (3) is grown using 30 sets of periodically alternating In layers. y Al 1-y As layer and In y Ga 1-y As layer composition, 0.75≤y≤0.85; where In y Al 1-y As layer and In y Ga 1-y The thickness of the As layers is 10~15nm, and the total thickness of the second buffer layer (3) is 600~900nm; the doping source of the second buffer layer (3) is Te, and the doping concentration is 5×10⁻⁶. 16 cm -3 ~1×10 17 cm -3 ; The absorber layer (5) is made of In 0.8 Ga 0.2 The absorber layer (5) is made of As and has a thickness of 2~2.5μm; the absorber layer (5) is made by unintentional doping.
2. The photodetector according to claim 1, characterized in that, The first ohmic contact layer (4) uses In 0.8 Al 0.2 The first ohmic contact layer (4) is made of As and has a thickness of 150~200 nm; the doping source of the first ohmic contact layer (4) is Te, and the doping concentration is 5×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
3. The photodetector according to claim 1, characterized in that, The thickness of the electron barrier layer (6) is 50~100nm; the electron barrier layer (6) is unintentionally doped.
4. The photodetector according to claim 1, characterized in that, The second ohmic contact layer (7) uses In 0.8 Al 0.2 The second ohmic contact layer (7) is made of As and has a thickness of 150~200 nm; the doping source of the second ohmic contact layer (7) is Te or Be, and the doping concentration is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
5. The photodetector according to claim 1, characterized in that, The substrate (1) is made of GaSb; the thickness of the substrate (1) is 50 μm.
6. A method for fabricating a photodetector, used to fabricate the photodetector according to any one of claims 1-5, characterized in that, include: A first buffer layer (2), a second buffer layer (3), a first ohmic contact layer (4), an absorption layer (5), an electronic barrier layer (6), and a second ohmic contact layer (7) are sequentially stacked on a substrate (1). The first buffer layer (2) uses In with a gradually changing In composition. x Al 1-x As composition; the second buffer layer (3) adopts multiple sets of periodically alternating stacked In y Al 1-y As layer and In y Ga 1-y The As layer is composed of an electron barrier layer (6) made of AlGaAsSb.