Photoelectric detector and method for preparing the same

Abstract

The present disclosure provides a photodetector, comprising: a substrate, an N-type contact layer, a collection layer, a cliff layer, an absorption layer, an electron blocking layer, a P-type contact layer, a passivation layer, a first through hole, a second through hole, a p-type electrode, an n-type electrode and a microlens, wherein the passivation layer is grown on the upper surface of the substrate, the upper surface and side surface of the N-type contact layer, the side surface of the collection layer and the cliff layer, the upper surface and side surface of the absorption layer, the side surface of the electron blocking layer and the upper surface and side surface of the P-type contact layer; the first through hole is opened on the passivation layer grown on the upper surface of the N-type contact layer; the second through hole is opened on the passivation layer grown on the upper surface of the P-type contact layer; the p-type electrode is grown in the first through hole and contacts the upper surface of the P-type contact layer; the n-type electrode is grown in the second through hole and contacts the upper surface of the N-type contact layer; the microlens is arranged on the lower surface of the substrate. The present disclosure also provides a method for preparing a photodetector.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optoelectronic devices, and in particular to a photodetector and a method for preparing the same. Background Art

[0002] A single-carrier photodiode (UTC) is a device in which photogenerated holes relax rapidly in picoseconds, and only electrons are transported in the device. Since the drift velocity of electrons is nearly an order of magnitude greater than that of holes, the space charge effect is effectively alleviated. It is the most suitable detector structure for high-power analog optical communication system receivers and has become a research hotspot in the field of optoelectronics in recent years. Currently, single-carrier photodiodes used in the communication field mainly include waveguide single-carrier photodiodes and surface-incident single-carrier photodiodes. The absorption layer thickness of the waveguide single-carrier photodiode is less than 1μm, while the diameter of the incident light spot is usually greater than 2μm. Due to the thin coupling cross section, it is difficult to obtain a high coupling efficiency with the incident optical fiber. The surface-incident single-carrier photodiode structure has a mutual restriction between responsivity and bandwidth due to the coupling of light signal absorption and carrier transport path. Therefore, single-carrier photodiodes cannot achieve high response and high-bandwidth light detection at the same time, which limits their application to a certain extent. Summary of the invention

[0003] In view of the above problems, the present disclosure provides a photodetector and a method for preparing the same.

[0004] According to a first aspect of the present disclosure, there is provided a photodetector comprising:

[0005] substrate;

[0006] An N-type contact layer is disposed in the middle of the upper surface of the substrate;

[0007] A collection layer, disposed in the middle of the upper surface of the N-type contact layer;

[0008] The cliff layer is set on the upper surface of the collection layer;

[0009] The absorption layer is set on the upper surface of the cliff layer;

[0010] An electron blocking layer is disposed in the middle of the upper surface of the absorption layer;

[0011] A P-type contact layer is disposed on the upper surface of the electron blocking layer;

[0012] A passivation layer, grown on the upper surface of the substrate, the upper surface and side surfaces of the N-type contact layer, the side surfaces of the collection layer and the cliff layer, the upper surface and side surfaces of the absorption layer, the side surfaces of the electron blocking layer, and the upper surface and side surfaces of the P-type contact layer;

[0013] A first through hole is opened on the passivation layer grown on the upper surface of the N-type contact layer;

[0014] A second through hole is formed on the passivation layer grown on the upper surface of the P-type contact layer;

[0015] A p-type electrode is grown in the first through hole and contacts the upper surface of the p-type contact layer;

[0016] An n-type electrode is grown in the second through hole and contacts the upper surface of the N-type contact layer;

[0017] The microlens is arranged on the lower surface of the substrate.

[0018] Optionally, the microlens comprises a monolithically integrated lens;

[0019] The focal length of the microlens is greater than the thickness of the substrate;

[0020] The contact area between the micro lens and the substrate is larger than the area of ​​the lower surface of the absorption layer.

[0021] Optionally, both the p-type electrode and the n-type electrode are coplanar electrode structures;

[0022] The photodetector includes M n-type electrodes, M=1 or M=2;

[0023] When M=2, the M n-type electrodes are symmetrically distributed about the collection layer, and the M n-type electrodes are connected to each other.

[0024] Optionally, the absorption layer includes an intrinsic absorption layer and a doping layer, the doping layer includes p-type doping, and the doping type of the doping layer includes any one of uniform doping and gradient doping;

[0025] The doping method of the doping layer includes any one of ion implantation and diffusion;

[0026] The intrinsic absorption layer includes a PN junction, and the PN junction is a buried junction.

[0027] Optionally, the photodetector detects wavelengths including infrared light bands.

[0028] Optionally, the width of the P-type contact layer is equal to the width of the electron blocking layer;

[0029] The width of the electron blocking layer is smaller than the width of the absorption layer;

[0030] The width of the absorbing layer is equal to the width of the cliff layer;

[0031] The width of the cliff layer is equal to the width of the collection layer;

[0032] The width of the collector layer is smaller than the width of the N-type contact layer.

[0033] According to a second aspect of the present disclosure, a method for preparing a photodetector is provided, the method comprising:

[0034] An N-type contact layer, a collection layer, a cliff layer, an absorption layer, an electron blocking layer and a P-type contact layer are sequentially grown on the upper surface of the substrate;

[0035] Etching a first predetermined area of ​​the electron blocking layer and the P-type contact layer to expose the absorption layer to form a first mesa;

[0036] etching a second predetermined region of the collection layer, the cliff layer, and the absorption layer to expose the N-type contact layer to form a second mesa;

[0037] Etching a third predetermined area of ​​the N-type contact layer to expose the substrate and form a third mesa;

[0038] A passivation layer is formed on the upper surface of the substrate, the upper surface and side surface of the N-type contact layer, the side surface of the collection layer and the cliff layer, the upper surface and side surface of the absorption layer, the side surface of the electron blocking layer, and the upper surface and side surface of the P-type contact layer;

[0039] Etching a fourth preset area of ​​the passivation layer to obtain a first through hole to expose the N-type contact layer;

[0040] preparing an n-type electrode in the first through hole;

[0041] Etching a fifth predetermined area of ​​the passivation layer to obtain a second through hole to expose the P-type contact layer;

[0042] preparing a p-type electrode in the second through hole;

[0043] thinning the substrate to a predetermined thickness;

[0044] A microlens is prepared on the lower surface of the substrate to obtain a photodetector.

[0045] Optionally, the preset thickness is 150-200 μm.

[0046] Optionally, the width of the first mesa is 5-12 μm, and the width of the second mesa is 15-20 μm.

[0047] Optionally, the etching method of the first mesa, the second mesa and the third mesa includes any one of ICP dry etching, wet etching, and ICP dry etching followed by wet etching. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 The schematic diagram of the structure of a photoelectric detector provided by an embodiment of the present disclosure is shown;

[0050] Figure 2 A schematic diagram of the structure of an absorption layer of a photodetector provided by an embodiment of the present disclosure is shown;

[0051] Figure 3 A schematic diagram schematically shows a process flow of a method for preparing a photoelectric detector provided by an embodiment of the present disclosure; and

[0052] Figures 4A to 4K The schematic diagram of the structure of the photoelectric detector in each step of a photoelectric detector preparation method provided by an embodiment of the present disclosure is schematically shown.

[0053] Description of reference numerals:

[0054] 1 substrate; 2 n-type contact layer; 3 collection layer; 4 cliff layer; 5 absorption layer; 6 electron blocking layer; 7 p-type contact layer; 8 passivation layer; 9 n-type electrode; 10 p-type electrode; 11 microlens; 51 intrinsic absorption layer; 52 doping layer. DETAILED DESCRIPTION

[0055] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0056] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0057] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0058] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). Those skilled in the art should also understand that any transitional conjunctions and / or phrases that substantially indicate two or more optional items, whether in the specification, claims, or drawings, should be understood to give the possibility of including one of these items, either of these items, or both of these items. For example, the phrase "A or B" should be understood to include the possibilities of "A" or "B", or "A and B".

[0059] The present invention provides a photodetector and a method for preparing the same. The photodetector comprises: a substrate; an N-type contact layer, arranged in the middle of the upper surface of the substrate; a collection layer, arranged in the middle of the upper surface of the N-type contact layer; a cliff layer, arranged on the upper surface of the collection layer; an absorption layer, arranged on the upper surface of the cliff layer; an electron blocking layer, arranged in the middle of the upper surface of the absorption layer; a P-type contact layer, arranged on the upper surface of the electron blocking layer; a passivation layer, grown on the upper surface of the substrate, the upper surface and side surface of the N-type contact layer, the collection layer and the cliff layer; The side of the cliff layer, the upper surface and side of the above-mentioned absorption layer, the side of the above-mentioned electron blocking layer, and the upper surface and side of the above-mentioned P-type contact layer; a first through hole, opened on the above-mentioned passivation layer grown on the upper surface of the above-mentioned N-type contact layer; a second through hole, opened on the above-mentioned passivation layer grown on the upper surface of the above-mentioned P-type contact layer; a p-type electrode, grown in the above-mentioned first through hole, and in contact with the upper surface of the above-mentioned P-type contact layer; an n-type electrode, grown in the above-mentioned second through hole, and in contact with the upper surface of the above-mentioned N-type contact layer; a microlens, arranged on the lower surface of the above-mentioned substrate. The photodetector provided by the present disclosure includes a three-level table, and the bandwidth and responsiveness of the device can be controlled by controlling the width of the three table tops, so that the photodetector can simultaneously achieve high-speed and high-response detection.

[0060] The following will be passed Figure 1-2 A photoelectric detector of the disclosed embodiment is described in detail to enable those skilled in the art to more clearly understand the technical solution of the present disclosure.

[0061] Figure 1 The structural diagram of a photoelectric detector provided by an embodiment of the present disclosure is schematically shown.

[0062] like Figure 1As shown, in one embodiment of the present disclosure, the photodetector includes: a substrate 1; an N-type contact layer 2, arranged in the middle of the upper surface of the substrate 1; a collection layer 3, arranged in the middle of the upper surface of the N-type contact layer 2; a cliff layer 4, arranged on the upper surface of the collection layer 3; an absorption layer 5, arranged on the upper surface of the cliff layer 4; an electron blocking layer 6, arranged in the middle of the upper surface of the absorption layer 5; a P-type contact layer 7, arranged on the upper surface of the electron blocking layer 6; a passivation layer 8, grown on the upper surface of the substrate 1, the upper surface and side of the N-type contact layer 2, the collection layer 3 and the cliff layer 4, the upper surface and side surface of the above-mentioned absorption layer 5, the side surface of the above-mentioned electron blocking layer 6 and the upper surface and side surface of the above-mentioned P-type contact layer 7; a first through hole is opened on the above-mentioned passivation layer 8 grown on the upper surface of the above-mentioned N-type contact layer 2; a second through hole is opened on the above-mentioned passivation layer 8 grown on the upper surface of the above-mentioned P-type contact layer 7; a p-type electrode 10 is grown in the above-mentioned first through hole and in contact with the upper surface of the above-mentioned P-type contact layer 7; an n-type electrode 9 is grown in the above-mentioned second through hole and in contact with the upper surface of the above-mentioned N-type contact layer 2; a microlens 11 is arranged on the lower surface of the above-mentioned substrate 1.

[0063] In this embodiment, the upper surface of the substrate 1 is sequentially provided with an N-type contact layer 2, a collection layer 3, a cliff layer 4, an absorption layer 5, an electron blocking layer 6 and a P-type contact layer 7, wherein the N-type contact layer 2 is provided in the middle of the upper surface of the substrate 1, the collection layer 3 is provided in the middle of the upper surface of the N-type contact layer 2, the electron blocking layer 6 is provided in the middle of the upper surface of the absorption layer 5, and the width of the P-type contact layer 7 is equal to the width of the electron blocking layer 6, the width of the electron blocking layer 6 is smaller than the width of the absorption layer 5, the width of the absorption layer 5 is equal to the width of the cliff layer 4, the width of the collection layer 3 is equal to the width of the collection layer 3, and the width of the collection layer 3 is smaller than the width of the N-type contact layer 2 (such as Figure 1As shown), the photodetector provided by the present invention includes three levels of mesas, namely, the mesas formed between the substrate 1 and the N-type contact layer 2, the mesas formed between the N-type contact layer 2 and the collection layer 3, and the mesas formed between the absorption layer 5 and the electron blocking layer 6. A passivation layer 8 is also grown on the upper surface of the above structure, that is, a passivation layer 8 is grown on the upper surface of the substrate 1, the upper surface and side surface of the N-type contact layer 2, the side surface of the collection layer 3 and the cliff layer 4, the upper surface and side surface of the absorption layer 5, the side surface of the electron blocking layer 6, and the upper surface and side surface of the P-type contact layer 7. A first through hole is opened in the passivation layer 8 on the upper surface of the N-type contact layer 2, and a second through hole is opened in the passivation layer 8 on the upper surface of the P-type contact layer 7. A p-type electrode 10 and an n-type electrode 9 are grown in the first through hole and the second through hole, respectively. The p-type electrode 10 and the n-type electrode 9 are both coplanar electrode structures. The photodetector in this embodiment includes M n-type electrodes 9, M=1 or M=2. When M=2, the M n-type electrodes 9 are symmetrically distributed about the collection layer 3, and the M n-type electrodes 9 are connected to each other. A microlens 11 is also provided on the lower surface of the substrate 1. The microlens 11 can be a monolithic integrated lens. The focal length of the microlens 11 in this embodiment is greater than the thickness of the substrate 1, and the contact area between the microlens 11 and the substrate 1 is greater than the area of ​​the lower surface of the absorption layer 5. In this embodiment, the detection wavelength of the photodetector provided by the present disclosure includes the infrared light band. The photodetector provided by the present disclosure includes a three-level table. By controlling the width of the three-level table, the bandwidth and responsivity of the device can be controlled. Specifically, by controlling the width of the table formed between the absorption layer 5 and the electron blocking layer 6, the junction area of ​​the PN junction can be controlled, thereby controlling the bandwidth of the device. By controlling the width of the table formed between the N-type contact layer 2 and the collection layer 3 (that is, the width of the absorption layer 5), the responsivity of the device can be controlled, so that the photodetector can simultaneously achieve high-speed and high-response detection.

[0064] It should be understood that the examples of the number of n-type electrodes, the detection wavelength of the photodetector, etc. in this embodiment are merely exemplary to help those skilled in the art understand the technical solution of the present disclosure, and are not intended to limit the protection scope of the present disclosure.

[0065] Figure 2 The schematic diagram shows the structure of an absorption layer of a photodetector provided in one embodiment of the present disclosure.

[0066] like Figure 2 As shown, in one embodiment of the present disclosure, the absorption layer 5 of the photodetector includes an intrinsic absorption layer 51 and a doping layer 52, the doping layer 52 includes p-type doping, and the doping type of the doping layer 52 includes any one of uniform doping and gradient doping; the doping method of the doping layer 52 includes any one of ion implantation and diffusion; the intrinsic absorption layer 51 includes a PN junction, and the PN junction is a buried junction.

[0067] In this embodiment, the absorption layer 5 includes an intrinsic absorption layer 51 and a doping layer 52. Figure 2 The intrinsic absorption layer 51 is close to the cliff layer 4, and the doping layer 52 is close to the electron blocking layer 6. The doping method of the doping layer 52 in this embodiment includes any one of ion implantation and diffusion. The specific doping method can be selected according to needs. The intrinsic absorption layer 51 in this embodiment includes a PN junction, and the PN junction is a buried junction.

[0068] It should be understood that Figure 1 and Figure 2 The photodetector shown in the figure is only exemplary to facilitate those skilled in the art to understand the solution of the present disclosure, and is not intended to limit the scope of protection of the present disclosure. In some other embodiments, the material, size, shape, etc. of each layer in the above-mentioned photodetector can be selected according to actual conditions and are not limited here.

[0069] Based on the above-mentioned photoelectric detector, the present disclosure also provides a method for preparing the photoelectric detector. Figure 3~Figure 4K The method is described in detail.

[0070] Figure 3 A schematic diagram of a process for preparing a photoelectric detector provided in an embodiment of the present disclosure is shown schematically. Figures 4A to 4K The schematic diagram of the structure of the photoelectric detector in each step of a photoelectric detector preparation method provided by an embodiment of the present disclosure is schematically shown.

[0071] like Figure 3 As shown, in one embodiment of the present disclosure, the method includes operations S301 to S311.

[0072] In operation S301 , an N-type contact layer, a collection layer, a cliff layer, an absorption layer, an electron blocking layer, and a P-type contact layer are sequentially grown on an upper surface of a substrate.

[0073] refer to Figure 4A and Figure 2 In this embodiment, an N-type contact layer, a collection layer, a cliff layer, an absorption layer, an electron blocking layer, and a P-type contact layer are grown on the upper surface of the substrate. The growth method in this embodiment includes metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or chemical vapor deposition (CVD). The doping concentration of the N-type contact layer can be 1×10 18 cm -3 ~3×10 19 cm -3 , preferably 1×10 19 cm -3The thickness can be 300nm to 800nm, preferably 500nm. The collection layer can be lightly n-doped or undoped, with a doping concentration of less than 2×10 15 / cm 3 , which can be preferably 1×10 15 / cm 3 , the collection layer can be InP or silicon. The cliff layer is n-type doped, and the doping concentration is less than 3×10 17 / cm 3 , which can be preferably 1.4×10 17 / cm 3 The thickness can be 30nm to 100nm, preferably 70nm. The doping layer in the absorption layer is p-type doped, and the doping concentration can be 1×10 18 cm -3 ~3×10 18 cm -3 Uniform doping, preferably gradient doping, forms a self-built electric field in the absorption layer to accelerate the drift motion of electrons. The thickness of the doped layer can be 100nm to 600nm, preferably 400nm, and the thickness of the intrinsic absorption layer can be 100 to 300nm, preferably 100nm. The electron blocking layer is p-type doped, and the doping concentration can be 1×10 18 cm -3 ~5×10 18 cm -3 , preferably 2×10 18 cm -3 The thickness can be 100nm to 300nm, preferably 100nm. The doping concentration of the P-type contact layer is greater than 1×10 19 / cm 3 , which can be preferably 3×10 19 / cm 3 The thickness can be 50nm to 100nm, preferably 80nm.

[0074] In operation S302 , first predetermined regions of the electron blocking layer and the P-type contact layer are etched to expose the absorption layer, thereby forming a first mesa.

[0075] refer to Figure 4B In this embodiment, a photoresist is applied to the area outside the first preset area on the upper surface of the P-type contact layer, and the photoresist is used as a mask. The P-type contact layer and the electron blocking layer outside the photoresist mask can be removed by photolithography, dry etching, and wet etching to form a first mesa. In this embodiment, the width of the first mesa is 5 to 12 μm.

[0076] In operation S303 , a second predetermined region of the collection layer, the cliff layer, and the absorption layer is etched to expose the N-type contact layer to form a second mesa.

[0077] refer to Figure 4C In this embodiment, photoresist is applied outside the second preset area on the upper surface of the absorption layer. The photoresist is used as a mask, and the collection layer, cliff layer and absorption layer outside the photoresist mask are removed by photolithography, dry etching and wet etching until the N-type contact layer is exposed to form a second mesa. In this embodiment, the width of the second mesa is 15 to 20 μm.

[0078] In operation S304 , a third predetermined region of the N-type contact layer is etched to expose the substrate and form a third mesa.

[0079] refer to Figure 4D In this embodiment, a photoresist is applied outside the third preset area on the upper surface of the N-type contact layer, and the photoresist is used as a mask. The N-type contact layer outside the photoresist mask is removed by photolithography, dry etching and wet etching to expose the substrate, thereby forming a second mesa.

[0080] In operation S305 , a passivation layer is prepared on the upper surface of the substrate, the upper surface and side surfaces of the N-type contact layer, the sides of the collection layer and the cliff layer, the upper surface and side surfaces of the absorption layer, the side surfaces of the electron blocking layer, and the upper surface and side surfaces of the P-type contact layer.

[0081] refer to Figure 4E In this embodiment, the material of the passivation layer can be silicon dioxide. When growing the silicon dioxide passivation layer, the device is firstly cleaned organically and inorganically, and then the silicon dioxide passivation layer is prepared by a plasma enhanced chemical vapor deposition system (PECVD) or an inductively coupled plasma vapor deposition system (ICPCVD). The thickness of the silicon dioxide passivation layer in this embodiment can be 200 to 1000 nm, preferably 500 nm.

[0082] In operation S306 , a fourth predetermined region of the passivation layer is etched to obtain a first through hole to expose the N-type contact layer.

[0083] refer to Figure 4F In this embodiment, a photoresist is selected as a mask, and a first through hole is opened in the fourth preset area of ​​the passivation layer by a reactive ion etching device (RIE) or a hydrofluoric acid solution corrosion method to expose the N-type contact layer.

[0084] In operation S307 , an n-type electrode is prepared in the first through hole.

[0085] refer to Figure 4GIn this embodiment, an n-type electrode is prepared in the first through hole, and the n-type electrode and the N-type contact layer are electrically connected to form a good ohmic contact. When the number of n-type electrodes is 2, the n-type electrodes are connected to each other. The material of the n-type electrode can be AuGeNi / Au alloy, Ti / Au, Ti / Pt / Au, etc. The method for preparing the n-type electrode includes any one of electron beam evaporation and magnetron sputtering.

[0086] In operation S308 , a fifth predetermined region of the passivation layer is etched to obtain a second through hole to expose the P-type contact layer.

[0087] refer to Figure 4H In this embodiment, a photoresist is selected as a mask, and a second through hole is opened in the fifth preset area of ​​the passivation layer by a reactive ion etching device (RIE) or a hydrofluoric acid solution corrosion method to expose the P-type contact layer.

[0088] In operation S309 , a p-type electrode is prepared in the second through hole.

[0089] refer to Fig. 4I In this embodiment, a p-type electrode is prepared in the second through hole, and the p-type electrode and the p-type contact layer are electrically connected to form a good ohmic contact. The material of the p-type electrode can be Ti / Au, Ti / Pt / Au, etc. The method for preparing the p-type electrode includes any one of electron beam evaporation and magnetron sputtering.

[0090] In operation S310, the substrate is thinned to a predetermined thickness.

[0091] refer to Figure 4J In this embodiment, in order to integrate the microlens, the substrate needs to be thinned. The thinning method may include manual thinning or machine thinning. The thinning liquid used for thinning may be Al2O3:H2O=1:3. In this embodiment, the preset thickness is 150-200 μm.

[0092] In operation S311, a microlens is prepared on the lower surface of the substrate to obtain a photodetector.

[0093] refer to Figure 4K In this embodiment, the shape of the microlens is defined by photolithography, and the excess photoresist is removed by development to retain the cylindrical pattern, which is then heated and melted so that the photoresist pattern presents a spherical crown-shaped microlens pattern. Finally, the microlens pattern is transferred to the back of the photodetector by ICP dry etching.

[0094] In this embodiment, the absorption layer includes a PN junction. Since the area of ​​the formed PN junction is determined by the area of ​​the first mesa, the area of ​​the PN junction is less than the area of ​​the second mesa, that is, the formed PN junction is a buried junction. Under this structure, only the area of ​​a part of the depleted region of the absorption layer contributes to the PN junction capacitance, and the area of ​​the entire absorption layer can absorb the incident light. It can be seen from the bandwidth formula of the photodetector that when the capacitance is small, the photodetector can achieve high bandwidth. The photodetector provided by the present disclosure can deplete the collection layer by increasing the reverse bias voltage. It can be seen from the capacitance formula C=εS / D that when the thickness D of the depletion region increases, the junction capacitance of the PN junction will be further reduced, where C is the capacitance, ε is the dielectric constant, S represents the area of ​​the collection layer, and D is the thickness. The etching method of the first mesa, the second mesa and the third mesa in this embodiment includes any one of ICP dry etching, wet etching, and ICP dry etching followed by wet etching.

[0095] It should be noted that the above description of the size, material, etc. of each layer in the photodetector is only exemplary to facilitate those skilled in the art to understand the scheme of the present disclosure, and is not intended to limit the scope of protection of the present disclosure. In some other embodiments, the size, material, etc. of each layer in the above photodetector can be selected according to actual conditions and are not limited here.

[0096] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0097] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the present disclosure has been shown and described with reference to specific exemplary embodiments of the present disclosure, it should be understood by those skilled in the art that various changes in form and detail may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the attached claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-mentioned embodiments, but should be determined not only by the attached claims, but also by the equivalents of the attached claims.

Claims

1. A photoelectric detector, characterized in that: include: Substrate (1); An N-type contact layer (2) is arranged in the middle of the upper surface of the substrate (1); A collection layer (3) is arranged in the middle of the upper surface of the N-type contact layer (2); A cliff layer (4), arranged on the upper surface of the collection layer (3); An absorption layer (5) disposed on the upper surface of the cliff layer (4); An electron blocking layer (6) is arranged in the middle of the upper surface of the absorption layer (5); A P-type contact layer (7) is arranged on the upper surface of the electron blocking layer (6); a passivation layer (8) grown on the upper surface of the substrate (1), the upper surface and side surfaces of the N-type contact layer (2), the side surfaces of the collection layer (3) and the cliff layer (4), the upper surface and side surfaces of the absorption layer (5), the side surfaces of the electron blocking layer (6), and the upper surface and side surfaces of the P-type contact layer (7); A first through hole is formed on the passivation layer (8) grown on the upper surface of the N-type contact layer (2); A second through hole is formed on the passivation layer (8) grown on the upper surface of the P-type contact layer (7); A p-type electrode (10) grown in the second through hole and in contact with the upper surface of the p-type contact layer (7); An n-type electrode (9) grown in the first through hole and in contact with the upper surface of the N-type contact layer (2); A microlens (11) is arranged on the lower surface of the substrate (1), Wherein, the width of the P-type contact layer (7) is equal to the width of the electron blocking layer (6); The width of the electron blocking layer (6) is smaller than the width of the absorption layer (5), a first mesa is formed between the electron blocking layer (6) and the absorption layer (5), and the width of the first mesa is 5 to 12 μm; The width of the absorption layer (5) is equal to the width of the cliff layer (4); The width of the cliff layer (4) is equal to the width of the collection layer (3); The width of the collection layer (3) is smaller than the width of the N-type contact layer (2); a second mesa is formed between the collection layer (3) and the N-type contact layer (2); the width of the second mesa is within a range of 15 to 20 μm.

2. The photodetector according to claim 1, characterized in that: The microlens (11) comprises a monolithic integrated lens; The focal length of the microlens (11) is greater than the thickness of the substrate (1); The contact area between the microlens (11) and the substrate (1) is larger than the area of ​​the lower surface of the absorption layer (5).

3. The photodetector according to claim 1, characterized in that: The p-type electrode (10) and the n-type electrode (9) are both coplanar electrode structures; The photodetector comprises M n-type electrodes (9), M=1 or M=2; When M=2, the M n-type electrodes (9) are symmetrically distributed about the collection layer (3), and the M n-type electrodes (9) are connected to each other.

4. The photodetector according to claim 1, characterized in that: The absorption layer (5) comprises an intrinsic absorption layer (51) and a doping layer (52), the doping layer (52) comprises p-type doping, and the doping type of the doping layer (52) comprises any one of uniform doping and gradient doping; The doping method of the doping layer (52) includes any one of ion implantation and diffusion; The intrinsic absorption layer (51) comprises a PN junction, and the PN junction is a buried junction.

5. The photodetector according to claim 1, characterized in that: The photoelectric detector detects wavelengths including infrared light bands.

6. A method for preparing a photodetector according to any one of claims 1 to 5, characterized in that: The method comprises: An N-type contact layer, a collection layer, a cliff layer, an absorption layer, an electron blocking layer and a P-type contact layer are sequentially grown on the upper surface of the substrate; Etching the first predetermined area of ​​the electron blocking layer and the P-type contact layer to expose the absorption layer to form a first mesa, wherein the width of the first mesa is 5-12 μm; Etching the collection layer, the cliff layer, and a second preset area of ​​the absorption layer to expose the N-type contact layer to form a second mesa, wherein the width of the second mesa is 15-20 μm; etching a third predetermined region of the N-type contact layer to expose the substrate and form a third mesa, Wherein, the width of the P-type contact layer is equal to the width of the electron blocking layer; The width of the electron blocking layer is smaller than the width of the absorption layer; The width of the absorption layer is equal to the width of the cliff layer; The width of the cliff layer is equal to the width of the collection layer; The width of the collecting layer is smaller than the width of the N-type contact layer; A passivation layer is prepared on the upper surface of the substrate, the upper surface and side surface of the N-type contact layer, the side surface of the collection layer and the cliff layer, the upper surface and side surface of the absorption layer, the side surface of the electron blocking layer, and the upper surface and side surface of the P-type contact layer; Etching a fourth preset area of ​​the passivation layer to obtain a first through hole to expose the N-type contact layer; preparing an n-type electrode in the first through hole; Etching a fifth preset area of ​​the passivation layer to obtain a second through hole to expose the P-type contact layer; preparing a p-type electrode in the second through hole; Thinning the substrate to a preset thickness; A microlens is prepared on the lower surface of the substrate to obtain the photodetector.

7. The method for preparing a photoelectric detector according to claim 6, characterized in that: The preset thickness is 150-200 μm.

8. The method for preparing a photoelectric detector according to claim 6, characterized in that: The etching method of the first mesa, the second mesa and the third mesa comprises any one of ICP dry etching, wet etching, and ICP dry etching followed by wet etching.

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