Avalanche photodetector and preparation method thereof

Abstract

The invention provides an avalanche photoelectric detector and a preparation method thereof, and relates to the technical field of photoelectric detectors and optoelectronic materials, and the avalanche photoelectric detector sequentially comprises an InP substrate, a first ohmic contact layer, a buffer layer, a multiplication layer, a charge control layer, a gradient layer, an absorption layer, a second ohmic contact layer and a cladding from bottom to top. Wherein the multiplication layer is made of AlGaAsSb (AlGaAsSb); the gradient layer is made of In < x > Al < y > Ga < 1-x-y > As in which the Al component is gradually changed and the In component is kept unchanged; and the absorption layer is made of a plurality of groups of In < x > Ga < 1-x > As and GaAs < y > Sb < 1-y > which are periodically and alternately stacked and grown. According to the invention, short-wave infrared detection of an expanded wavelength and a relatively high signal-to-noise ratio can be realized, carrier capture caused by band gap difference can be effectively reduced, and lattice strain at an interface can be reduced, so that the defect density can be reduced, the injection efficiency of carriers from an absorption layer to a multiplication layer can be optimized, and the performance of the device can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detectors and optoelectronic materials, and in particular to an avalanche photoelectric detector and a preparation method thereof. Background Art

[0002] Short-wave infrared (SWIR) photodetectors (detection wavelength 1~3μm) have important application value in many fields, such as: Light Laser Detection and Ranging (LiDAR), gas detection, medical imaging and optical communication systems. Avalanche photodiode (APD) has become a key technology in high-sensitivity photodetection because of its photogenerated carrier multiplication effect. The response wavelength and noise characteristics of APD depend on the material selection of the absorption layer and the multiplication layer.

[0003] In terms of response wavelength, the APD device based on InP substrate and using lattice-matched InGaAs absorption layer has a response cutoff wavelength of , which is difficult to meet the requirements of complex environment imaging and gas detection. Special requirements of the above short-wave infrared bands.

[0004] In terms of noise characteristics, the commonly used short-wave infrared APD multiplication layers mainly include InP (hole injection multiplication layer), InAlAs (electron injection multiplication layer) and other materials. Since the effective mass of electrons is smaller than that of holes, a faster drift speed can be obtained, thereby improving the response speed of APD devices. In electron injection APD devices, InAlAs is used as a multiplication layer, and the ratio k (k=β / α) of the hole and electron ionization coefficients (β and α) is large, which will introduce significant excess noise, thereby limiting the detection capability of weak signals.

[0005] In terms of material band gap or lattice constant differences, the working principle of APD requires that after the photogenerated carriers are generated in the absorption layer, they quickly pass through the interface into the multiplication layer for avalanche multiplication. However, due to the difference in material band gaps between different layers, carriers are often captured at the interface, which hinders the effective transmission of carriers. In traditional APD designs, the absorption layer and the multiplication layer often use semiconductor materials with different band gaps, which makes the transmission of carriers between different band gap layers face huge obstacles, especially in high-responsivity and low-noise application scenarios. The carrier capture problem caused by the band gap difference is more significant. In addition, the lattice constant mismatch often occurs when selecting materials for the absorption layer and the multiplication layer, especially at the junction between different compound semiconductor materials, the lattice strain phenomenon is particularly prominent. If it cannot be effectively alleviated, the performance of the device will be seriously restricted. Existing solutions usually use different epitaxial growth techniques or interface treatment methods to alleviate the band gap difference and lattice mismatch problems, but these methods often cannot fundamentally solve the long-term performance problems caused by band gap differences and lattice constant mismatch. At the same time, traditional material design and structural layout have limited effects on improving carrier injection efficiency, and there are still certain technical bottlenecks. Summary of the invention

[0006] The present invention provides an avalanche photodetector and a preparation method thereof, which are used to achieve short-wave infrared detection with extended wavelength and a higher signal-to-noise ratio, and effectively reduce carrier capture caused by band gap differences, reduce lattice strain at the interface, thereby reducing defect density, and optimize the injection efficiency of carriers from the absorption layer to the multiplication layer, thereby improving device performance.

[0007] The present invention provides an avalanche photodetector, which comprises, from bottom to top, an InP substrate, a first ohmic contact layer, a buffer layer, a multiplication layer, a charge control layer, a gradient layer, an absorption layer, a second ohmic contact layer and a cladding layer; The multiplication layer is made of AlGaAsSb; the gradient layer is made of In with a gradient Al composition and a constant In composition. x Al y Ga 1-x-y The absorption layer is made of multiple groups of In x Ga 1-x As and GaAs y Sb 1-y Made.

[0008] According to an avalanche photodetector provided by the present invention, the first ohmic contact layer is made of InP lattice matching. 0.53 Ga 0.47 As, the thickness of the first ohmic contact layer is 300-500 nm; the doping source of the first ohmic contact layer is Te, and the doping concentration is 7×1018 cm -3 ~2×10 19 cm -3 .

[0009] According to an avalanche photodetector provided by the present invention, the buffer layer is made of Al 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the buffer layer is 200-400 nm; the doping source of the buffer layer is Te, and the doping concentration is 9×10 17 cm -3 ~2×10 18 cm -3 .

[0010] According to an avalanche photodetector provided by the present invention, the multiplication layer is made of intrinsically doped Al that matches the InP substrate lattice. 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the multiplication layer is 1000-1500 nm.

[0011] According to an avalanche photodetector provided by the present invention, the charge control layer is made of Al 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the charge control layer is 135-150 nm; the doping source of the charge control layer is Be, and the doping concentration is 1×10 16 cm -3 ~2×10 16 cm -3 , the doping type is p-type doping.

[0012] According to an avalanche photodetector provided by the present invention, In x Al y Ga 1-x-y The Al component of As decreases along the direction from the charge control layer to the absorption layer.

[0013] According to an avalanche photodetector provided by the present invention, the Al component of the gradient layer decreases from 0.4 to 0.1, and 0.1≤y≤0.4.

[0014] According to the avalanche photodetector provided by the present invention, the gradient layer is divided into three layers in total, and the thickness of each layer is 15 nm.

[0015] According to an avalanche photodetector provided by the present invention, the absorption layer is formed by 150 groups of unintentionally doped Inx Ga 1-x As and GaAs y Sb 1-y Made of, 0.5≤x≤0.7, 0.4≤y≤0.5, each group In x Ga 1-x As and GaAs y Sb 1-y The thickness of each layer is 3-5 nm, and the total thickness of the absorption layer is 1300-1500 nm.

[0016] According to an avalanche photodetector provided by the present invention, the second ohmic contact layer is made of InP lattice matching. 0.53 Ga 0.47 As, the thickness of the second ohmic contact layer is 160-200 nm; the doping source of the second ohmic contact layer is Be, and the doping concentration is 9×10 17 cm -3 ~2×10 18 cm -3 .

[0017] According to an avalanche photodetector provided by the present invention, the cladding layer is made of In 0.53 Ga 0.47 As, the cladding has a thickness of 30-50 nm; the doping source of the cladding is Be, and the doping concentration is 7×10 18 cm -3 ~2×10 19 cm -3 .

[0018] The present invention also provides a method for preparing an avalanche photodetector, comprising: The first ohmic contact layer, buffer layer, multiplication layer, charge control layer, gradient layer, absorption layer, second ohmic contact layer and cladding layer of the epitaxial wafer are grown in sequence from bottom to top on the InP substrate by molecular beam epitaxy technology; wherein the multiplication layer is made of AlGaAsSb; the gradient layer is made of In with a gradient Al composition and a constant In composition x Al y Ga 1-x-y The absorption layer is made of multiple groups of In x Ga 1-x As and GaAs y Sb 1-y Made of; Cleaning the epitaxial wafer, and growing a sacrificial silicon dioxide layer on the cleaned epitaxial wafer; Coating a layer of first photoresist on the silicon dioxide sacrificial layer, and performing photolithography on the first photoresist to form a patterned first photoresist; Using the patterned first photoresist as a mask, etching the silicon dioxide sacrificial layer to form a patterned silicon dioxide sacrificial layer; removing the remaining first photoresist and performing cleaning; Using the patterned silicon dioxide sacrificial layer as a mask, etching the epitaxial wafer to form an epitaxial wafer having a terrace; removing the remaining sacrificial silicon dioxide layer; Depositing a passivation layer on the epitaxial wafer having the terrace; Coating a layer of second photoresist on the passivation layer, and performing photolithography on the second photoresist to form a patterned second photoresist; Using the patterned second photoresist as a mask, the passivation layer is corroded to expose the electrode window; removing the remaining second photoresist and performing cleaning; A metal layer is grown by magnetron sputtering process; Coating a layer of third photoresist on the metal layer, and performing photolithography on the third photoresist to form a patterned third photoresist; Using the patterned third photoresist as a mask, the metal layer is corroded to form an electrode; removing the remaining third photoresist and performing cleaning; The back side of the epitaxial wafer with the terrace is thinned and polished, and the final avalanche photodetector is obtained after dicing and cleavage.

[0019] The present invention provides an avalanche photodetector and a method for preparing the same. The avalanche photodetector includes, from bottom to top, an InP substrate, a first ohmic contact layer, a buffer layer, a multiplication layer, a charge control layer, a gradient layer, an absorption layer, a second ohmic contact layer, and a cladding layer. The multiplication layer is made of AlGaAsSb. Using AlGaAsSb, a low-k material, as the multiplication layer can effectively reduce the excess noise factor of the avalanche photodetector and achieve a higher signal-to-noise ratio. The gradient layer uses In with a gradient Al component and a constant In component. x Al y Ga 1-x-y As, using In x Al y Ga 1-x-y As a graded layer, the problem caused by the difference in material band gap or lattice constant can be alleviated by changing the Al composition, effectively reducing the carrier capture caused by the band gap difference, reducing the lattice strain at the interface, thereby reducing the defect density and optimizing the injection efficiency of carriers from the absorption layer to the multiplication layer, thereby improving the device performance. x Ga 1-xAs and GaAs y Sb 1-y The invention adopts an InGaAs / GaAsSb superlattice structure to replace the traditional InGaAs as the absorption layer, and expands the response wavelength from 1.55 μm to 2 μm, so as to realize short-wave infrared detection with an extended wavelength. Therefore, the invention can realize short-wave infrared detection with an extended wavelength and a higher signal-to-noise ratio, and effectively reduce the carrier capture caused by the band gap difference, reduce the lattice strain at the interface, thereby reducing the defect density, and optimize the injection efficiency of carriers from the absorption layer to the multiplication layer, thereby improving the device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of the structure of an avalanche photodetector provided in an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of the k value suppression of antimonide provided in an embodiment of the present invention.

[0023] Figure 3 Schematic diagram of two types of superlattice energy bands provided by an embodiment of the present invention.

[0024] Figure 4 It is a schematic flow chart of a method for preparing an avalanche photodetector provided in an embodiment of the present invention.

[0025] Figure 5 It is a schematic diagram of the process flow of a method for preparing an avalanche photodetector provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Combine the following Figure 1-Figure 5 The avalanche photodetector and the method for making the same are described.

[0028] Please refer to Figure 1 , Figure 1Schematic diagram of the structure of an avalanche photodetector provided by an embodiment of the present invention. Figure 1 As shown, the avalanche photodetector includes, from bottom to top, an InP substrate 1, a first ohmic contact layer 2, a buffer layer 3, a multiplication layer 4, a charge control layer 5, a gradient layer 6, an absorption layer 7, a second ohmic contact layer 8 and a cladding layer 9.

[0029] The InP substrate 1 is made of InP, and the thickness of the InP substrate 1 may be 320 μm.

[0030] Optionally, the first ohmic contact layer 2 is made of InP lattice matching. 0.53 Ga 0.47 As, the thickness of the first ohmic contact layer 2 is 300-500 nm. The doping source of the first ohmic contact layer 2 is Te, and the doping concentration is 7×10 18 cm -3 ~2×10 19 cm -3 .

[0031] Optionally, the buffer layer 3 is made of Al 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the buffer layer 3 is 200-400 nm. The doping source of the buffer layer 3 is Te, and the doping concentration is 9×10 17 cm -3 ~2×10 18 cm -3 .

[0032] The multiplication layer 4 is made of AlGaAsSb. The low-k material AlGaAsSb is used as the multiplication layer 4. The introduction of antimony (Sb) element significantly increases the splitting energy level of the valence band of the multiplication layer and keeps it away from the heavy hole and light hole energy bands, which can effectively suppress hole ionization and reduce the k value, thereby effectively reducing the excess noise factor of the avalanche photodetector, achieving a higher signal-to-noise ratio, and improving the performance of the multiplication layer 4.

[0033] Optionally, the multiplication layer 4 is made of intrinsically doped Al that matches the InP substrate lattice. 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the multiplication layer 4 is 1000~1500nm.

[0034] Experiments have shown that the introduction of antimony (Sb) can reduce the k value. Specifically, Figure 2 Figure (a) shows the transition process of holes, and the arrows indicate the movement paths of holes. By increasing the energy of the spin-split coupling band, such as Figure 2As shown in Figure (b), the spin-splitting coupling energy level and the light and heavy hole bands are separated, the collision ionization of holes located in the heavy hole band is suppressed, and the collision ionization coefficient ratio of electrons and holes increases, that is, the k value decreases.

[0035] Optionally, the charge control layer 5 is made of Al 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the charge control layer 5 is 135-150 nm. The doping source of the charge control layer 5 is Be, and the doping concentration is 1×10 16 cm -3 ~2×10 16 cm -3 , the doping type is p-type doping.

[0036] The graded layer 6 uses an In layer with a graded Al composition and a constant In composition. x Al y Ga 1-x-y Made of As. x Al y Ga 1-x-y As is used as the gradient layer 6, and can alleviate the problems caused by the difference in material band gap or lattice constant by changing the Al component, effectively reduce the carrier capture caused by the band gap difference, reduce the lattice strain at the interface, thereby reducing the defect density, and optimize the injection efficiency of carriers from the absorption layer 7 to the multiplication layer 4, thereby improving the device performance.

[0037] Optionally, the gradient layer 6 has In x Al y Ga 1-x-y The Al component of As decreases gradually along the direction from the charge control layer 5 to the absorption layer 7 .

[0038] Optionally, the Al composition of the graded layer 6 decreases from 0.4 to 0.1, 0.1≤y≤0.4.

[0039] Optionally, the gradient layer 6 is divided into three layers in total, and the thickness of each layer is 15 nm.

[0040] The absorption layer 7 is made of multiple groups of In x Ga 1-x As and GaAs y Sb 1-y Made. Figure 3As shown, the material system of the InGaAs / GaAsSb type II superlattice structure has a high conduction band energy band offset and a low valence band energy band offset. Therefore, using the InGaAs / GaAsSb superlattice structure instead of the traditional InGaAs as the absorption layer 7 can effectively extend the response wavelength from 1.55μm to more than 2μm, and can achieve short-wave infrared detection with extended wavelength.

[0041] Optionally, the absorption layer 7 is formed by 150 groups of unintentionally doped In x Ga 1-x As and GaAs y Sb 1-y Made of, 0.5≤x≤0.7, 0.4≤y≤0.5, each group In x Ga 1-x As and GaAs y Sb 1-y The thickness of each layer is 3-5 nm, and the total thickness of the absorption layer 7 is 1300-1500 nm.

[0042] Optionally, the second ohmic contact layer 8 is made of InP lattice matching. 0.53 Ga 0.47 As, the thickness of the second ohmic contact layer 8 is 160-200 nm. The doping source of the second ohmic contact layer 8 is Be, and the doping concentration is 9×10 17 cm -3 ~2×10 18 cm -3 .

[0043] Optionally, the cladding 9 is made of In 0.53 Ga 0.47 As, the thickness of cladding 9 is 30~50nm. The doping source of cladding 9 is Be, and the doping concentration is 7×10 18 cm -3 ~2×10 19 cm -3 .

[0044] The avalanche photodetector provided by the embodiment of the present invention includes, from bottom to top, an InP substrate, a first ohmic contact layer, a buffer layer, a multiplication layer, a charge control layer, a gradient layer, an absorption layer, a second ohmic contact layer, and a cladding layer. The multiplication layer is made of AlGaAsSb. Using AlGaAsSb, a low-k material, as the multiplication layer can effectively reduce the excess noise factor of the avalanche photodetector and achieve a higher signal-to-noise ratio. The gradient layer uses In with a gradient Al composition and a constant In composition. x Al y Ga 1-x-y As, using In x Aly Ga 1-x-y As a graded layer, the problem caused by the difference in material band gap or lattice constant can be alleviated by changing the Al composition, effectively reducing the carrier capture caused by the band gap difference, reducing the lattice strain at the interface, thereby reducing the defect density and optimizing the injection efficiency of carriers from the absorption layer to the multiplication layer, thereby improving the device performance. x Ga 1-x As and GaAs y Sb 1-y The invention adopts an InGaAs / GaAsSb superlattice structure to replace the traditional InGaAs as the absorption layer, and expands the response wavelength from 1.55 μm to 2 μm, so as to realize short-wave infrared detection with an extended wavelength. Therefore, the embodiment of the present invention can realize short-wave infrared detection with an extended wavelength and a higher signal-to-noise ratio, and effectively reduce the carrier capture caused by the band gap difference, reduce the lattice strain at the interface, thereby reducing the defect density, and optimize the injection efficiency of carriers from the absorption layer to the multiplication layer, thereby improving the device performance.

[0045] The following is a description of a method for preparing the avalanche photodetector provided by the present invention. The method for preparing the avalanche photodetector described below and the avalanche photodetector described above can be referred to in correspondence with each other.

[0046] Please refer to Figure 4 , Figure 4 FIG. 1 is a flow chart of a method for preparing an avalanche photodetector provided by an embodiment of the present invention. Figure 4 As shown, the method may include steps 401 to 416.

[0047] Step 401, using molecular beam epitaxy technology to sequentially grow the first ohmic contact layer, buffer layer, multiplication layer, charge control layer, gradient layer, absorption layer, second ohmic contact layer and cladding layer of the epitaxial wafer from bottom to top on the InP substrate; wherein the multiplication layer is made of AlGaAsSb; the gradient layer is made of InxAl with a gradient Al composition and a constant In composition; y Ga 1-x-y As; the absorption layer is made of multiple groups of In x Ga 1-x As and GaAs y Sb 1-y Made.

[0048] Specifically, the multiplication layer is made of AlGaAsSb. Using AlGaAsSb, a low-k material, as the multiplication layer can effectively reduce the excess noise factor of the avalanche photodetector and achieve a higher signal-to-noise ratio.

[0049] The graded layer uses an In layer with a gradual change in Al composition and a constant In composition. x Al y Ga 1-x-y As, using In x Al y Ga 1-x-y As a graded layer, As can alleviate the problems caused by differences in material band gap or lattice constant by changing the Al component, effectively reduce carrier capture caused by band gap differences, reduce lattice strain at the interface, thereby reducing defect density, and optimize the injection efficiency of carriers from the absorption layer to the multiplication layer, thereby improving device performance.

[0050] The absorption layer is made of multiple groups of In x Ga 1-x As and GaAs y Sb 1-y It uses InGaAs / GaAsSb superlattice structure instead of traditional InGaAs as the absorption layer, extending the response wavelength from 1.55μm to 2μm, and can realize short-wave infrared detection with extended wavelength.

[0051] Step 402: clean the epitaxial wafer, and grow a sacrificial silicon dioxide layer on the cleaned epitaxial wafer.

[0052] Specifically, Figure 5 As shown in Figure (a), the epitaxial wafer is cleaned. Figure 5 As shown in Figure (b), a sacrificial silicon dioxide layer is grown on the cleaned epitaxial wafer.

[0053] Step 403 , coating a layer of first photoresist on the silicon dioxide sacrificial layer, and performing photolithography on the first photoresist to form a patterned first photoresist.

[0054] Specifically, Figure 5 As shown in Figure (c), a first photoresist layer is coated on the silicon dioxide sacrificial layer. Figure 5 As shown in FIG. 5( d ), the first photoresist is subjected to photolithography to form a patterned first photoresist.

[0055] Step 404 , using the patterned first photoresist as a mask, etching the silicon dioxide sacrificial layer to form a patterned silicon dioxide sacrificial layer.

[0056] Specifically, Figure 5 As shown in FIG. 5( e ), the silicon dioxide sacrificial layer is etched using the patterned first photoresist as a mask to form a patterned silicon dioxide sacrificial layer.

[0057] Step 405: remove the remaining first photoresist and perform cleaning.

[0058] Specifically, Figure 5 As shown in FIG. 5( f ), the remaining first photoresist is removed and cleaning is performed.

[0059] Step 406 , using the patterned silicon dioxide sacrificial layer as a mask, etching the epitaxial wafer to form an epitaxial wafer with a terrace.

[0060] Specifically, Figure 5 As shown in Figure (g), the epitaxial wafer is etched using the patterned silicon dioxide sacrificial layer as a mask to form an epitaxial wafer with a terrace.

[0061] Step 407: remove the remaining silicon dioxide sacrificial layer.

[0062] Specifically, Figure 5 As shown in Figure (h), the remaining silicon dioxide sacrificial layer is removed.

[0063] Step 408 : depositing a passivation layer on the epitaxial wafer having the mesa.

[0064] Specifically, Figure 5 As shown in Figure (i), a passivation layer is deposited on the epitaxial wafer with a terrace. The material of the passivation layer can be silicon dioxide.

[0065] Step 409 , coating a layer of second photoresist on the passivation layer, and performing photolithography on the second photoresist to form a patterned second photoresist.

[0066] Specifically, Figure 5 As shown in Figure (j), a second photoresist is coated on the passivation layer. Figure 5 As shown in FIG. 7 (k), the second photoresist is subjected to photolithography to form a patterned second photoresist.

[0067] Step 410: Use the patterned second photoresist as a mask to etch the passivation layer to expose the electrode window.

[0068] Specifically, Figure 5 As shown in FIG. 1 (l), the patterned second photoresist is used as a mask to etch the passivation layer to expose the electrode window.

[0069] Step 411: remove the remaining second photoresist and perform cleaning.

[0070] Specifically, Figure 5 As shown in FIG. 7 (m), the remaining second photoresist is removed and cleaning is performed.

[0071] Step 412: grow a metal layer using a magnetron sputtering process.

[0072] Specifically, Figure 5As shown in Figure (n), a metal layer is grown by magnetron sputtering process. The material of the metal layer is Ti or Au.

[0073] Step 413 , coating a layer of third photoresist on the metal layer, and performing photolithography on the third photoresist to form a patterned third photoresist.

[0074] Specifically, Figure 5 As shown in FIG. 8( o ), a third photoresist is coated on the metal layer.

[0075] Step 414: Use the patterned third photoresist as a mask to etch the metal layer to form an electrode.

[0076] Step 415: remove the remaining third photoresist and perform cleaning.

[0077] Step 416: thinning and polishing the back side of the epitaxial wafer with the terrace, and obtaining the final avalanche photodetector after dicing and cleavage.

[0078] Specifically, Figure 5 After photolithography, etching, stripping, cleaning, thinning, polishing and dicing, the (o) pattern is obtained. Figure 5 The avalanche photodetector shown in Figure (p).

[0079] It should be noted that the epitaxial wafer may also be grown in other ways, and this embodiment is not limited to the molecular beam epitaxy technology.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An avalanche photodetector, characterized in that: From bottom to top, it includes: InP substrate, first ohmic contact layer, buffer layer, multiplication layer, charge control layer, gradient layer, absorption layer, second ohmic contact layer and cladding layer; The multiplication layer is made of AlGaAsSb; the gradient layer is made of In with a gradient Al composition and a constant In composition. x Al y Ga 1-x-y The absorption layer is made of multiple groups of In x Ga 1-x As and GaAs y Sb 1-y Made.

2. The avalanche photodetector according to claim 1, characterized in that: The first ohmic contact layer is made of InP lattice matching 0.53 Ga 0.47 As, the thickness of the first ohmic contact layer is 300-500 nm; the doping source of the first ohmic contact layer is Te, and the doping concentration is 7×10 18 cm -3 ~2×10 19 cm -3 .

3. The avalanche photodetector according to claim 1, characterized in that: The buffer layer is made of Al 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the buffer layer is 200-400 nm; the doping source of the buffer layer is Te, and the doping concentration is 9×10 17 cm -3 ~2×10 18 cm -3 .

4. The avalanche photodetector according to claim 1, characterized in that: The multiplication layer is made of intrinsically doped Al that matches the InP substrate lattice. 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the multiplication layer is 1000-1500 nm.

5. The avalanche photodetector according to claim 1, characterized in that: The charge control layer is made of Al 0.75 Ga 0.25 As 0.55 Sb 0.45 The thickness of the charge control layer is 135-150 nm; the doping source of the charge control layer is Be, and the doping concentration is 1×10 16 cm -3 ~2×10 16 cm -3 , the doping type is p-type doping.

6. The avalanche photodetector according to claim 1, characterized in that: In the gradient layer x Al y Ga 1-x-y The Al component of As decreases gradually along the direction from the charge control layer to the absorption layer.

7. The avalanche photodetector according to claim 6, characterized in that: The Al component of the gradient layer decreases from 0.4 to 0.1, 0.1≤y≤0.

4.

8. The avalanche photodetector according to claim 6 or 7, characterized in that: The gradient layer is divided into three layers in total, and the thickness of each layer is 15 nm.

9. The avalanche photodetector according to claim 1, characterized in that: The absorption layer is formed by 150 groups of unintentionally doped In x Ga 1-x As and GaAs y Sb 1-y Made of, 0.5≤x≤0.7, 0.4≤y≤0.5, each group In x Ga 1-x As and GaAs y Sb 1-y The thickness of each layer is 3-5 nm, and the total thickness of the absorption layer is 1300-1500 nm.

10. The avalanche photodetector according to claim 1, characterized in that: The second ohmic contact layer is made of InP lattice matching 0.53 Ga 0.47 As, the thickness of the second ohmic contact layer is 160-200 nm; the doping source of the second ohmic contact layer is Be, and the doping concentration is 9×10 17 cm -3 ~2×10 18 cm -3 .

11. The avalanche photodetector according to claim 1, characterized in that: The cladding layer is made of In 0.53 Ga 0.47 As, the cladding has a thickness of 30-50 nm; the doping source of the cladding is Be, and the doping concentration is 7×10 18 cm -3 ~2×10 19 cm -3 .

12. A method for preparing an avalanche photodetector, characterized in that: include: The first ohmic contact layer, buffer layer, multiplication layer, charge control layer, gradient layer, absorption layer, second ohmic contact layer and cladding layer of the epitaxial wafer are grown in sequence from bottom to top on the InP substrate by molecular beam epitaxy technology; wherein the multiplication layer is made of AlGaAsSb; the gradient layer is made of In with a gradient Al composition and a constant In composition x Al y Ga 1-x-y The absorption layer is made of multiple groups of In x Ga 1-x As and GaAs y Sb 1-y Made of; Cleaning the epitaxial wafer, and growing a sacrificial silicon dioxide layer on the cleaned epitaxial wafer; Coating a layer of first photoresist on the silicon dioxide sacrificial layer, and performing photolithography on the first photoresist to form a patterned first photoresist; Using the patterned first photoresist as a mask, etching the silicon dioxide sacrificial layer to form a patterned silicon dioxide sacrificial layer; removing the remaining first photoresist and performing cleaning; Using the patterned silicon dioxide sacrificial layer as a mask, etching the epitaxial wafer to form an epitaxial wafer having a terrace; removing the remaining sacrificial silicon dioxide layer; Depositing a passivation layer on the epitaxial wafer having the terrace; Coating a layer of second photoresist on the passivation layer, and performing photolithography on the second photoresist to form a patterned second photoresist; Using the patterned second photoresist as a mask, the passivation layer is corroded to expose the electrode window; removing the remaining second photoresist and performing cleaning; A metal layer is grown by magnetron sputtering process; Coating a layer of third photoresist on the metal layer, and performing photolithography on the third photoresist to form a patterned third photoresist; Using the patterned third photoresist as a mask, the metal layer is corroded to form an electrode; removing the remaining third photoresist and performing cleaning; The back side of the epitaxial wafer with the terrace is thinned and polished, and the final avalanche photodetector is obtained after dicing and cleavage.

Images