Indium phosphide-based waveguide detector and preparation method thereof

Abstract

An indium phosphide-based waveguide detector and a preparation method thereof, the detector comprising: an indium phosphide substrate; an epitaxial structure layer deposited on the indium phosphide substrate, the epitaxial structure layer comprising: a first ohmic contact layer formed on the indium phosphide substrate; an enhanced absorption layer formed on the first ohmic contact layer, the enhanced absorption layer forming a cladding-absorption layer-cladding structure for absorbing light waves in the infrared band; a second ohmic contact layer formed on the enhanced absorption layer; wherein the overall refractive index of the enhanced absorption layer is greater than that of the first ohmic contact layer and the second ohmic contact layer; a first electrode connected to the first ohmic contact layer; and a second electrode connected to the second ohmic contact layer.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic devices, and in particular to an indium phosphide-based waveguide detector and a preparation method thereof. Background Art

[0002] With the rapid development of 5G communication, big data and the Internet of Things, the demand for data traffic has increased dramatically. At present, the transmission rate of optical communication has gradually increased from 40G / 100G to 200G / 400G (such as IEEE 802.3ba and 802.3bs standards). Research on optical receiving systems adapted to optical communications has also developed rapidly. Photodetectors are key components of optical receiving systems. Among them, edge-incident waveguide detectors realize the decoupling of light absorption and carrier transport directions, overcoming the problem that traditional vertical-incident photodetectors cannot simultaneously meet the high quantum efficiency and large bandwidth, and have attracted much attention. The coupling modes of waveguide detectors are divided into evanescent wave coupling and butt coupling. Evanescent wave coupling refers to the coupling of incident light into a relatively long (tens of μm) waveguide layer, and then gradually transmitting the light to the absorption layer through the evanescent wave effect at the interface between the waveguide layer and the absorption layer. Butt coupling is to dock the input waveguide with the absorption layer, directly couple the incident light into the absorption layer, and simultaneously realize light transmission and light absorption through the absorption layer.

[0003] Currently, waveguide detectors cannot achieve efficient and high-speed light detection at the same time, which limits their application to a certain extent. Summary of the invention

[0004] In view of this, the main purpose of the present disclosure is to provide an InP-based waveguide detector and a method for preparing the same, in order to partially solve at least one of the above-mentioned technical problems.

[0005] In order to achieve the above object, one aspect of the present disclosure provides an indium phosphide-based waveguide detector, comprising:

[0006] An indium phosphide substrate; an epitaxial structure layer deposited on the indium phosphide substrate, the epitaxial structure layer comprising: a first ohmic contact layer formed on the indium phosphide substrate; an enhanced absorption layer formed on the first ohmic contact layer, the enhanced absorption layer forming a cladding-absorption layer-cladding structure for absorbing light waves in the infrared band; a second ohmic contact layer formed on the enhanced absorption layer; a first electrode connected to the first ohmic contact layer; and a second electrode connected to the second ohmic contact layer.

[0007] According to an embodiment of the present disclosure, it also includes: a silicon dioxide passivation layer, covering the indium phosphide substrate outside the epitaxial structure layer, and covering the area on the epitaxial structure layer except the first electrode and the second electrode; a polyimide planarization layer, covering the silicon dioxide passivation layer.

[0008] According to an embodiment of the present disclosure, the enhanced absorption layer includes: a first cladding layer, which is formed in sequence from the first ohmic contact layer to the top: a first cladding layer, the refractive index of the first cladding layer is greater than the refractive index of the first ohmic contact layer and the second ohmic contact layer; an absorption layer, the refractive index of the absorption layer is greater than the refractive index of the first cladding layer; and a second cladding layer, the preset refractive index of the second cladding layer is greater than the refractive index of the first ohmic contact layer and the second ohmic contact layer, and less than the refractive index of the absorption layer; wherein the enhanced absorption layer utilizes the change of the refractive index of the structure within the layer and the change of the refractive index with the first ohmic contact layer and the second ohmic contact layer to absorb light waves in the infrared band.

[0009] According to an embodiment of the present disclosure, the thickness of the first cladding is determined by the refractive index of the first cladding; the thickness of the second cladding is determined by the refractive index of the second cladding; and the thickness of the absorption layer is less than 1 μm.

[0010] According to an embodiment of the present disclosure, the first cladding material includes InGaAsP or InAlGaAs; and the second cladding material includes InGaAsP or InAlGaAs.

[0011] According to an embodiment of the present disclosure, the above-mentioned first cladding material includes InGaAsP or InAlGaAs, the doping type includes n-type doping, and the doping ions include any one of silicon, tellurium, and carbon; the above-mentioned second cladding material includes InGaAsP or InAlGaAs, the doping type includes p-type doping, and the doping ions include beryllium or zinc; and the material, doping type and doping ions of the above-mentioned first cladding can be interchangeable with those of the second cladding.

[0012] According to an embodiment of the present disclosure, the material of the first ohmic contact layer includes InP or GaAs, the doping type includes n-type doping, and the doping ions include any one of silicon, tellurium, and carbon; the material of the second ohmic contact layer includes InP or GaAs, the doping type includes p-type doping, and the doping ions include beryllium or zinc; the material, doping type and doping ions of the first ohmic contact layer can be interchangeable with those of the second ohmic contact layer; and the polarity of the first ohmic contact layer is consistent with that of the first cladding layer, and the polarity of the second ohmic contact layer is consistent with that of the second cladding layer.

[0013] According to an embodiment of the present disclosure, the above-mentioned doping method may include in-situ doping or diffusion.

[0014] According to an embodiment of the present disclosure, the first electrode material includes AuGeNi / Au alloy; the second electrode material includes Ti / Au or Ti / Pt / Au; the material of the first electrode can be interchangeable with the second electrode; and the polarity of the first electrode is consistent with the first ohmic contact layer, and the polarity of the second electrode is consistent with the second ohmic contact layer.

[0015] According to an embodiment of the present disclosure, the dielectric constant of the polyimide planarization layer is smaller than the dielectric constant of the silicon dioxide passivation layer.

[0016] Another aspect of the present disclosure provides a method for preparing an indium phosphide-based waveguide detector, comprising:

[0017] The epitaxial structure layer is grown on the indium phosphide substrate, and the first ohmic contact layer, the first cladding layer, the absorption layer, the second cladding layer, and the second ohmic contact layer are grown in sequence from the indium phosphide substrate upward; the first mesa is formed by photolithography and / or etching outside the epitaxial structure layer, including the second ohmic contact layer, the second cladding layer, the absorption layer and the first cladding layer; after obtaining the first mesa, the second mesa is formed by photolithography and / or etching outside the epitaxial structure layer, and the second mesa includes the first ohmic contact layer; the epitaxial structure layer is passivated outside to form a silicon dioxide passivation layer; the first mesa is exposed on the silicon dioxide passivation layer by photolithography and etching. A table contact window; forming a polyimide planarization layer on the silicon dioxide passivation layer by photolithography and curing; exposing a second table contact window on the silicon dioxide passivation layer by photolithography and etching; performing ion beam sputtering and / or stripping treatment on the epitaxial structure layer to form a first electrode; performing ion beam sputtering and / or stripping treatment on the epitaxial structure layer to form a second electrode; performing thinning treatment on the indium phosphide substrate to thin the other side of the substrate relative to the epitaxial structure layer, wherein the thickness of the indium phosphide substrate after thinning is less than 150 μm; performing cleavage on the indium phosphide substrate and the epitaxial structure layer grown thereon to obtain the indium phosphide-based waveguide detector of a preset size.

[0018] According to the above-mentioned InP-based waveguide detector and its preparation method, the guided mode of the transmitted light in the InP-based waveguide detector can be expanded in the longitudinal direction of transmission through the epitaxial layer structure, thereby increasing the coupling efficiency between the transmitted light and the incident optical fiber and improving the detector's responsiveness.

[0019] Based on the above technical solutions, it can be seen that the embodiments of the present disclosure have the following beneficial effects compared with the prior art:

[0020] The indium phosphide-based waveguide detector provided by the present disclosure can expand the guided mode in the indium phosphide-based waveguide detector in the longitudinal direction by adding a first cladding layer of a medium light refractive index material between the absorption layer and the first ohmic contact layer and adding a second cladding layer of a medium light refractive index material between the absorption layer and the second ohmic contact layer, thereby increasing the coupling efficiency with the incident optical fiber and improving the responsiveness of the indium phosphide-based waveguide detector.

[0021] The absorption layer thickness of the indium phosphide-based waveguide detector provided by the present disclosure is at the sub-micron level, which reduces the transit time of carriers and the dark current of the device, and improves the bandwidth and signal-to-noise ratio of the indium phosphide-based waveguide detector.

[0022] The polyimide planarization layer of the indium phosphide-based waveguide detector provided by the present disclosure reduces the parasitic capacitance of the device and improves the response speed of the indium phosphide-based waveguide detector.

[0023] The indium phosphide-based waveguide detector provided by the present disclosure can achieve an optical coupling efficiency of more than 90% when the size is small. Compared with other existing structures, the structure and process are simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematically shows a cross-sectional view of an indium phosphide-based waveguide detector according to an embodiment of the present disclosure;

[0025] Figure 2 The flowchart of the method for preparing an indium phosphide-based waveguide detector according to an embodiment of the present disclosure is schematically shown.

[0026] 1-Indium phosphide substrate;

[0027] 2-first ohmic contact layer;

[0028] 3- first cladding;

[0029] 4- Absorption layer;

[0030] 5- second cladding;

[0031] 6- second ohmic contact layer;

[0032] 7-Silicon dioxide passivation layer;

[0033] 8-polyimide planarization layer;

[0034] 9- a first electrode;

[0035] 9-1- first a electrode;

[0036] 9-2- first b electrode;

[0037] 10- a second electrode;

[0038] 20- Strengthen the absorption layer. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] 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.

[0042] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not 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.).

[0043] In the process of implementing the concept of the present disclosure, the inventors found that there are at least the following problems in the related art:

[0044] The coupling modes of waveguide detectors can be divided into two types: evanescent wave coupling and butt coupling. The transmission mode of evanescent wave coupling is sensitive to defects and dislocations of the material at the interface, which is not conducive to the transport of carriers. At present, the thickness of the absorption layer of the waveguide detector using butt coupling is less than 1μm, while the incident spot diameter of the transmitted light is usually greater than 2μm. Due to the thin coupling cross section, it is difficult to obtain high coupling efficiency with the incident optical fiber using butt coupling. At present, waveguide detectors cannot achieve efficient and high-speed light detection at the same time, which limits their application to a certain extent.

[0045] In order to at least partially solve the technical problems existing in the related art, one aspect of the present disclosure provides an indium phosphide-based waveguide detector.

[0046] Figure 1A cross-sectional schematic diagram of an indium phosphide-based waveguide detector according to an embodiment of the present disclosure is schematically shown.

[0047] like Figure 1 As shown, the indium phosphide-based waveguide detector includes: an indium phosphide substrate 1; an epitaxial structure layer deposited on the indium phosphide substrate 1, the epitaxial structure layer including: a first ohmic contact layer 2 formed on the indium phosphide substrate 1; an enhanced absorption layer 20 formed on the first ohmic contact layer 2, the enhanced absorption layer 20 forming a cladding-absorption layer-cladding structure for absorbing light waves in the infrared band; a second ohmic contact layer 6 formed on the enhanced absorption layer 20; a first electrode 9 connected to the first ohmic contact layer 2; and a second electrode 10 connected to the second ohmic contact layer 6.

[0048] More specifically, the material used for the indium phosphide substrate 1 may be semi-insulating InP.

[0049] According to the embodiments of the present disclosure, the chemical formulas are respectively expressed as InGaAsP (indium gallium arsenic phosphide), InAlGaAs (indium aluminum gallium arsenide), InP (indium phosphide), GaAs (gallium arsenide), Ti (titanium), Pt (platinum), and Au (gold).

[0050] According to an embodiment of the present disclosure, the enhanced absorption layer 20 includes the following layers formed sequentially from the first ohmic contact layer 2 to the top:

[0051] The first cladding layer 3 has a refractive index greater than the refractive indexes of the first ohmic contact layer 2 and the second ohmic contact layer 6 .

[0052] The absorption layer 4 has a refractive index greater than that of the first cladding layer 3 .

[0053] The second cladding layer 5 has a preset refractive index that is greater than the refractive indexes of the first ohmic contact layer 2 and the second ohmic contact layer 6 , and is less than the refractive index of the absorption layer 4 .

[0054] And the absorption layer 4 has a thickness less than 1 μm.

[0055] More specifically, the material of the absorption layer 4 may be InGaAs. Preferably, the material of the absorption layer is InGa 0.53 As 0.47 The absorption layer 4 can be undoped or doped in a partially p-doped uniform manner or a partially p-doped gradient manner. When undoped, the impurity concentration of the absorption layer 4 is less than 1×10 15 / cm 3 , when partial p uniform doping or partial p gradient doping is performed, the impurity concentration is greater than 1×10 15 / cm 3The doping type and impurity concentration may be selected according to the required refractive index of the absorption layer 4. The thickness of the absorption layer 4 may be 100-300 nm, and preferably, the thickness of the absorption layer is 200 nm.

[0056] According to an embodiment of the present disclosure, the first cladding layer 3 material includes InGaAsP or InAlGaAs;

[0057] The material of the second cladding layer 5 includes InGaAsP or InAlGaAs.

[0058] More specifically, when the material of the first cladding layer 3 is n-doped, a partial n-uniform doping method can be used. The doping ions include any one of silicon, tellurium, and carbon. The n-type doping allows the first cladding layer 3 to provide electrons to the outside, and the polarity of the first cladding layer 3 is defined as positive when the n-type doping is performed.

[0059] More specifically, when the material of the second cladding layer 5 is p-doped so that the second cladding layer 5 can receive electrons from the outside, it is defined that the polarity of the second cladding layer 5 is negative when the p-doping is performed.

[0060] The material, doping type and doping ions of the first cladding layer 3 can be interchanged with those of the second cladding layer 5 .

[0061] And the first cladding layer 3 and the second cladding layer 5 may not be doped.

[0062] More specifically, when the first cladding 3 and the second cladding 5 are not doped, the charge state of the materials of the first cladding 3 and the second cladding 5 is not changed. During the detection process of the detector, the applied reverse bias depletes the first cladding 3 and the second cladding 5. The first cladding 3 and the second cladding 5 are equivalent to being merged with the absorption layer 4, thereby increasing the thickness of the absorption layer 4 and reducing the overall capacitance of the enhanced absorption layer 20.

[0063] According to an embodiment of the present disclosure, the thickness of the first cladding layer 3 is determined by the refractive index of the first cladding layer 3 ; the thickness of the second cladding layer 5 is determined by the refractive index of the second cladding layer 5 .

[0064] More specifically, the material type, doping type and / or the concentration of doping ions during doping of the first cladding 3 determine the refractive index of the first cladding 3. First claddings 3 with different refractive indices can be obtained by changing the material type, doping type and / or the concentration of doping ions during doping. The refractive index of the second cladding 5 is determined in a similar manner to that of the first cladding 3, and will not be described in detail herein.

[0065] Under the condition that the refractive index of the first cladding 3 is greater than the refractive index of the first ohmic contact layer 2 and less than the absorption layer 4, and the refractive index of the second cladding 5 is greater than the refractive index of the second ohmic contact layer 6 and less than the absorption layer 4, the first cladding 3 and the second cladding 5 with different refractive indices can be obtained by changing the material type, doping type and / or concentration of doping ions during doping of the first cladding 3 and the second cladding 5.

[0066] The thickness of the first cladding layer 3 and the second cladding layer 5 are determined according to the material type, the doping type and / or the concentration of doping ions during doping, and the refractive index.

[0067] According to an embodiment of the present disclosure, the material of the first ohmic contact layer 2 includes InP or GaAs, the doping type includes n-type doping, the doping ions include any one of silicon, tellurium, and carbon, and the polarity of the first ohmic contact layer 2 is defined as positive when n-type doping is performed.

[0068] More specifically, the thickness of the first ohmic contact layer 2 may be 300-1000 nm, and preferably, the thickness of the first ohmic contact layer 2 is 500 nm. The impurity concentration of the first ohmic contact layer 2 is greater than 1×10 18 / cm 3 .

[0069] The material of the second ohmic contact layer 6 includes InP or GaAs, the doping type includes p-type doping, the doping ions include beryllium or zinc, and it is defined that the polarity of the second ohmic contact layer 6 is negative when p-type doping is performed.

[0070] More specifically, the thickness of the second ohmic contact layer 6 may be 80-100 nm. Preferably, the thickness of the second ohmic contact layer 6 is 100 nm. The impurity concentration of the second ohmic contact layer 6 is greater than 1×10 19 / cm 3 .

[0071] The material, doping type and doping ions of the first ohmic contact layer 2 can be interchanged with those of the second ohmic contact layer 6; and

[0072] The polarity of the first ohmic contact layer 2 is consistent with that of the first cladding layer 3 , and the polarity of the second ohmic contact layer 6 is consistent with that of the second cladding layer 5 .

[0073] More specifically, the first cladding layer 3 and the first ohmic contact layer 2 maintain the same doping type, and the second cladding layer 5 and the second ohmic contact layer 6 maintain the same doping type.

[0074] According to an embodiment of the present disclosure, the material of the first electrode 9 includes AuGeNi / Au alloy.

[0075] The material of the second electrode 10 includes Ti / Au or Ti / Pt / Au.

[0076] The material of the first electrode 9 can be interchanged with that of the second electrode 10.

[0077] The polarity of the first electrode 9 is consistent with that of the first ohmic contact layer 2 , and the polarity of the second electrode 10 is consistent with that of the second ohmic contact layer 6 .

[0078] More specifically, it is defined that the first electrode 9 is made of AuGeNi / Au alloy to present a positive polarity; and it is defined that the second electrode 10 is made of Ti / Au or Ti / Pt / Au to present a negative polarity.

[0079] Furthermore, when the first cladding layer 3 and the second cladding layer are not doped, it is only necessary to make the polarity of the first electrode 9 consistent with the first ohmic contact layer 2 , and the polarity of the second electrode 10 consistent with the second ohmic contact layer 6 .

[0080] According to an embodiment of the present disclosure, the refractive index of the absorption layer 4 formed in the epitaxial structure layer of the indium phosphide-based waveguide detector is greater than the refractive index of the first cladding 3 and the second cladding 5, and the refractive index of the first cladding 3 and the second cladding 5 is greater than the refractive index of the first ohmic contact layer 2 and the second ohmic contact layer 6.

[0081] By forming the epitaxial structure layer with the above refractive index relationship, when the indium phosphide-based waveguide detector detects the transmission light, the transmission light is transmitted in the enhanced absorption layer 20 and absorbed by the absorption layer 4. During the transmission of the transmission light in the enhanced absorption layer 20, the spot size of the transmission light guide mode is expanded, thereby increasing the optical coupling efficiency between the waveguide and the waveguide detector.

[0082] More specifically, the transmission light is infrared light. The transmission light guide mode can be a variety of transmission light modes that can be detected by the detector. The waveguide can be an incident optical fiber or a structure that guides the transmission light in any direction.

[0083] According to the embodiments of the present disclosure, the detection speed of the indium phosphide-based waveguide detector is related to the detection bandwidth of the detector. The larger the detection bandwidth, the faster the detection speed. The detection bandwidth can be calculated by the following formula (1):

[0084]

[0085] Among them, F is the detection bandwidth; R is the total resistance of the detector; C is the total capacitance of the detector; v is the carrier drift velocity; D1 is the thickness of the absorption layer.

[0086] Improving the detection bandwidth can be achieved by reducing the total detector capacitance C, the total detector resistance R of the device, increasing the carrier drift velocity v and / or reducing the absorption layer thickness D1.

[0087] According to the embodiments of the present disclosure, the detection bandwidth can be adjusted according to actual needs by adjusting the refractive indices of the first cladding 3 and the second cladding 5 in the epitaxial structure layer having the above-mentioned refractive index relationship, and adjusting the refractive indices of the first ohmic contact layer 2 and the second ohmic contact layer 6.

[0088] More specifically, when adjusting the first cladding 3 and the second cladding 5, for the undoped case, the first cladding 3 and the second cladding 5 are merged with the absorption layer 4, and the carrier drift width increases, resulting in a decrease in the carrier drift velocity v, but the total capacitance C of the detector decreases accordingly; for the doped case, the first cladding 3, the absorption layer 4 and the second cladding 5 form a semiconductor structure, the carrier drift velocity v increases, but the total capacitance C of the detector increases compared to the undoped case. The specific parameters of the epitaxial structure layer of the indium phosphide-based waveguide detector can be selected according to the actual use requirements of the indium phosphide-based waveguide detector to obtain the optimal detection bandwidth value, thereby achieving the effect of improving the detection speed of the indium phosphide-based waveguide detector.

[0089] According to the embodiments of the present disclosure, the thickness of the absorption layer 4 of the indium phosphide-based waveguide detector can be 100-300nm, preferably 200nm. The thickness of the absorption layer of the waveguide detector with the same coupling efficiency is generally greater than the submicron level. The indium phosphide-based waveguide detector provided by the present disclosure forms an epitaxial structure layer with the above-mentioned refractive index relationship, so that the guided mode of the transmitted light in the indium phosphide-based waveguide detector is expanded in the longitudinal direction, thereby increasing the coupling efficiency with the incident optical fiber and improving the responsiveness of the detector.

[0090] According to the embodiments of the present disclosure, the thickness of the absorption layer 4 of the indium phosphide-based waveguide detector is at the sub-micron level, which reduces the transit time of carriers and the dark current of the device, and improves the bandwidth and signal-to-noise ratio of the detector.

[0091] According to an embodiment of the present disclosure, the indium phosphide-based waveguide detector further includes: a silicon dioxide passivation layer 7, an indium phosphide substrate 1 covering the outside of the epitaxial structure layer, and a region covering the epitaxial structure layer except the first electrode 9 and the second electrode 10.

[0092] More specifically, the thickness of the silicon dioxide passivation layer 7 is 400-1000 nm, and preferably, the thickness of the silicon dioxide passivation layer 7 may be 500 nm. The silicon dioxide passivation layer 7 is used to protect the epitaxial structure layer and the indium phosphide substrate 1 .

[0093] More specifically, a first mesa contact window is opened on the silicon dioxide passivation layer 7 to expose the second ohmic contact layer 6 , and the second electrode 10 is disposed in the first mesa contact window.

[0094] A second mesa contact window is opened on the silicon dioxide passivation layer 7, exposing the first ohmic contact layer 2. The second mesa contact window includes a second mesa contact a window and a second mesa contact b window. A first a electrode 9-1 is arranged in the second mesa contact a window, and a first b electrode 9-2 is arranged in the second mesa contact b window.

[0095] The polyimide planarization layer 8 covers the silicon dioxide passivation layer 7 .

[0096] The thickness of the polyimide planarization layer 8 may be 1-3 μm.

[0097] According to an embodiment of the present disclosure, the dielectric constant of the polyimide planarization layer 8 is smaller than the dielectric constant of the silicon dioxide passivation layer 7 .

[0098] More specifically, the dielectric constant of the polyimide can be set to 2.9, which is less than the dielectric constant of 3.9 of the silicon dioxide passivation layer 7. When the polyimide planarization layer 8 covers the silicon dioxide passivation layer 7, the height difference between the silicon dioxide passivation layer covering the epitaxial structure layer and the silicon dioxide passivation layer covering the indium phosphide substrate 1 outside the epitaxial structure layer is reduced, that is, a polyimide planarization layer 8 with a thickness of D2 is formed around the first electrode.

[0099] The total capacitance of the detector may include parasitic capacitance. According to the capacitance formula C=εS / D2, by selecting a polyimide material with a small dielectric constant ε and a large thickness D2, and controlling the contact area S between the polyimide planarization layer 8 formed by the polyimide material and the electrode, a smaller parasitic capacitance is obtained, thereby obtaining a smaller total capacitance of the detector, thereby improving the detection bandwidth of the indium phosphide-based waveguide detector and improving the response speed of the indium phosphide-based waveguide detector.

[0100] According to the embodiments of the present disclosure, by forming an epitaxial structure layer with the above-mentioned refractive index relationship, the spot size of the guided mode in the InP-based waveguide detector is expanded, and the optical coupling efficiency between the waveguide and the InP-based waveguide detector is increased; by using a butt coupling method, light is directly coupled from the waveguide to the absorption material, and the absorption efficiency per unit length of the InP-based waveguide detector is increased; by using the design of the polyimide flattening layer 8, the parasitic capacitance of the InP-based waveguide detector is reduced, and the response speed of the InP-based waveguide detector is improved; and a silicon dioxide passivation structure is used to improve the stability of the InP-based waveguide detector. The InP-based waveguide detector structure provided by the present invention can be prepared by traditional photolithography and etching processes, and the preparation process is simple, meeting the detection requirements of high response, high speed and high signal-to-noise ratio.

[0101] Another aspect of the present disclosure provides a method for preparing an InP-based waveguide detector.

[0102] Figure 2The flowchart of the method for preparing an indium phosphide-based waveguide detector according to an embodiment of the present disclosure is schematically shown.

[0103] like Figure 2 As shown, the method for preparing an InP-based waveguide detector includes steps S101-S111.

[0104] Step S101 , growing epitaxial structural layers on an indium phosphide substrate 1 , and sequentially growing a first ohmic contact layer 2 , a first cladding layer 3 , an absorption layer 4 , a second cladding layer 5 , and a second ohmic contact layer 6 from the indium phosphide substrate 1 upward.

[0105] According to an embodiment of the present disclosure, a method for growing an epitaxial structure layer may include: Metal-organic Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE) or Chemical Vapor Deposition (CVD).

[0106] Step S102 , performing photolithography and / or etching processing on the outside of the epitaxial structure layer to form a first mesa, including a second ohmic contact layer 6 , a second cladding layer 5 , an absorption layer 4 and a first cladding layer 3 .

[0107] According to an embodiment of the present disclosure, preparing the first mesa may include: removing the second ohmic contact layer 6 , the upper cladding layer 5 , the absorption layer 4 , and the lower cladding layer 3 outside the photoresist mask by photolithography and / or etching to expose the first ohmic contact layer 2 .

[0108] According to an embodiment of the present disclosure, the width of the first mesa can be controlled when preparing the first mesa, wherein the width of the first mesa is controlled to be equal to the width of the absorption layer 4, which can be 3-5 μm.

[0109] Step S103 , after obtaining the first mesa, performing photolithography and / or etching processing outside the epitaxial structure layer to form a second mesa, the second mesa including the first ohmic contact layer 2 .

[0110] According to an embodiment of the present disclosure, the first ohmic contact layer 2 may be formed into a "convex" structure by photolithography and / or etching. The width of the second mesa is greater than that of the first mesa, and the width of the second mesa may be 30-50 μm.

[0111] According to an embodiment of the present disclosure, when preparing the first mesa and the second mesa, the etching process may include an inductively coupled plasma (ICP) dry etching method, a wet etching method, or a two-step method of ICP dry etching followed by wet etching. When using ICP dry etching, the pattern transfer is accurate; when using wet etching, a smooth mesa etching morphology can be obtained; when using the two-step method of ICP dry etching followed by wet etching, the obtained pattern transfer is highly accurate, the mesa sidewall is smooth, and the increased dark current caused by damage to the mesa sidewall is avoided.

[0112] Step S104: performing a passivation treatment on the outside of the epitaxial structure layer to form a silicon dioxide passivation layer 7.

[0113] According to an embodiment of the present invention, forming the silicon dioxide passivation layer 7 may include: after the device obtained in step S103 is cleaned, using a plasma enhanced chemical vapor deposition (PECVD) system or an inductively coupled plasma vapor deposition (ICPCVD) system to prepare the silicon dioxide passivation layer 7.

[0114] Step S105 , exposing a first mesa contact window on the silicon dioxide passivation layer 7 by photolithography and etching.

[0115] According to an embodiment of the present invention, preparing the first mesa electrode contact may include: using photoresist as a mask, opening a first mesa contact window by reactive ion etching (RIE) equipment or HF acid (hydrofluoric acid) etching to expose a portion of the second ohmic contact layer 6.

[0116] Step S106 , forming a polyimide planarization layer 8 on the silicon dioxide passivation layer 7 by photolithography and curing.

[0117] According to an embodiment of the present invention, a first mesa contact window pattern and a second mesa contact window pattern are defined on the silicon dioxide passivation layer 7 by using a photosensitive polyimide material and then cured to form a polyimide planarization layer 8 .

[0118] Step S107 , exposing a second mesa contact window on the silicon dioxide passivation layer 7 by photolithography and etching.

[0119] Step S108 , performing ion beam sputtering and / or stripping treatment on the epitaxial structure layer to form a first electrode 9 .

[0120] According to an embodiment of the present invention, the first electrode 9 includes a first a-electrode 9-1 and a first b-electrode 9-2. Figure 1 As shown, the length of the absorption layer 4 between the first a-electrode 9-1 and the first b-electrode 9-2 is the width of the absorption layer 4, which can be 3-5 μm. The first a-electrode 9-1 and the first b-electrode 9-2 are electrically connected to the first ohmic contact layer 2 to form a good ohmic contact.

[0121] Step S109 , performing ion beam sputtering and / or lift-off treatment on the epitaxial structure layer to form a second electrode 10 .

[0122] According to the embodiment of the present invention, the second electrode 10 and the second ohmic contact layer 6 are electrically connected to form a good ohmic contact.

[0123] According to an embodiment of the present invention, it is necessary to lead out the first electrode 9 and the second electrode 10 through electrode leads, and connect the probe of a source voltage meter to the electrode leads. A bias voltage of corresponding polarity is applied to the first electrode 9 and the second electrode 10 through the source voltage meter so that the indium phosphide-based waveguide detector can work normally, and the low dielectric constant of the polyimide material of the polyimide planarization layer 8 is used to reduce the parasitic capacitance of the electrode leads.

[0124] Step S110 , thinning the indium phosphide substrate 1 to thin the other side of the substrate relative to the epitaxial structure layer, and the thickness of the indium phosphide substrate 1 after thinning is less than 150 μm.

[0125] According to an embodiment of the present invention, the thinning method may include at least one of the following: manual thinning or machine thinning, and the solute ratio of the thinning liquid used for thinning may be Al 2 O 3 :H 2 O=1:3.

[0126] Step S111, cleaving the indium phosphide substrate 1 and the structural layer grown thereon to obtain an indium phosphide-based waveguide detector of a predetermined size.

[0127] According to an embodiment of the present invention, the device obtained through steps S101 to S110 is precisely cleaved to obtain the final length size of the InP-based waveguide probe. The length of the InP-based waveguide probe may be 10-20 μm.

[0128] According to the embodiments of the present invention, other types of substrates or other materials can also be used to prepare waveguide detectors, and as long as the relevant structures are met, they should also be included in the protection scope of the present invention.

[0129] It should also be noted that the implementations not described in the specification or drawings are all forms known to those skilled in the art and are not described in detail. The directional terms mentioned in the embodiments, such as "up", "down", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present invention. Demonstrations containing specific values ​​may be provided herein, but these parameters do not need to be exactly equal to the corresponding values, but may be approximately equal to the corresponding values ​​within an acceptable error tolerance or design constraint. Furthermore, in the preparation method, the steps, unless specifically described or must occur in sequence, are not limited to those listed above and may be changed or rearranged according to the desired design.

[0130] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. An indium phosphide-based waveguide detector, include: Indium phosphide substrate; An epitaxial structure layer deposited on the indium phosphide substrate, the epitaxial structure layer comprising: A first ohmic contact layer is formed on the indium phosphide substrate; An enhanced absorption layer is formed on the first ohmic contact layer, and the enhanced absorption layer forms a cladding-absorption layer-cladding structure, and is used for absorbing light waves in the infrared band; A second ohmic contact layer is formed on the enhanced absorption layer; Wherein, the overall refractive index of the enhanced absorption layer is greater than that of the first ohmic contact layer and the second ohmic contact layer; a first electrode connected to the first ohmic contact layer; and a second electrode connected to the second ohmic contact layer; Wherein, the enhanced absorption layer includes the following layers formed in sequence from the first ohmic contact layer upward: A first cladding layer is directly formed on the first ohmic contact layer and is in contact with the first ohmic contact layer, wherein the refractive index of the first cladding layer is greater than the refractive indexes of the first ohmic contact layer and the second ohmic contact layer; an absorbing layer, the absorbing layer having a refractive index greater than the refractive index of the first cladding layer; and a second cladding layer, wherein a preset refractive index of the second cladding layer is greater than the refractive indexes of the first ohmic contact layer and the second ohmic contact layer, and is less than the refractive index of the absorption layer; The enhanced absorption layer absorbs light waves in the infrared band by utilizing the change of the refractive index of the structure within the layer and the change of the refractive index of the first ohmic contact layer and the second ohmic contact layer; The first cladding layer, the absorption layer and the second cladding layer are all undoped.

2. The detector according to claim 1, further comprising: include: A silicon dioxide passivation layer covering the indium phosphide substrate outside the epitaxial structure layer and covering the area on the epitaxial structure layer except the first electrode and the second electrode; A polyimide planarization layer covers the silicon dioxide passivation layer.

3. The detector according to claim 1, in, The thickness of the first cladding is determined by the refractive index of the first cladding; The thickness of the second cladding is determined by the refractive index of the second cladding; and The thickness of the absorption layer is less than 1 μm.

4. The detector according to claim 1, in, The material of the first cladding layer includes InGaAsP or InAlGaAs; The material of the second cladding layer includes InGaAsP or InAlGaAs.

5. The detector according to claim 4, in, The material of the first ohmic contact layer includes InP or GaAs, the doping type includes n-type doping, and the doping ions include any one of silicon, tellurium, and carbon; The material of the second ohmic contact layer includes InP or GaAs, the doping type includes p-type doping, and the doping ions include beryllium or zinc; The material, doping type, and doping ions of the first ohmic contact layer may be interchanged with the material, doping type, and doping ions of the second ohmic contact layer.

6. The detector according to claim 5, in, The material of the first electrode includes AuGeNi / Au alloy; The material of the second electrode includes Ti / Au or Ti / Pt / Au; The material of the first electrode can be interchangeable with the material of the second electrode; as well as The polarity of the first electrode is consistent with the polarity of the first ohmic contact layer, and the polarity of the second electrode is consistent with the polarity of the second ohmic contact layer.

7. The detector according to claim 2, in, The dielectric constant of the polyimide planarization layer is smaller than the dielectric constant of the silicon dioxide passivation layer.

8. A method for preparing the indium phosphide-based waveguide detector according to any one of claims 1 to 7, include: Growing epitaxial structural layers on an indium phosphide substrate, and sequentially growing a first ohmic contact layer, a first cladding layer, an absorption layer, a second cladding layer, and a second ohmic contact layer from the indium phosphide substrate upward; Performing photolithography and / or etching processing outside the epitaxial structure layer to form a first mesa, wherein the first mesa includes the second ohmic contact layer, the second cladding layer, the absorption layer and the first cladding layer; After obtaining the first mesa, performing photolithography and / or etching processing outside the epitaxial structure layer to form a second mesa, wherein the second mesa includes the first ohmic contact layer; Performing a passivation treatment on the outside of the epitaxial structure layer to form a silicon dioxide passivation layer; Exposing a first mesa contact window on the silicon dioxide passivation layer by photolithography and etching; forming a polyimide planarization layer on the silicon dioxide passivation layer by photolithography and curing; Exposing a second mesa contact window on the silicon dioxide passivation layer by photolithography and etching; Performing ion beam sputtering and / or stripping treatment on the epitaxial structure layer to form a first electrode; Performing ion beam sputtering and / or stripping treatment on the epitaxial structure layer to form a second electrode; Performing a thinning process on the indium phosphide substrate, thinning the other side of the substrate relative to the epitaxial structure layer, wherein the thickness of the indium phosphide substrate after thinning is less than 150 μm; The indium phosphide substrate and the structural layer grown thereon are cleaved to obtain the indium phosphide-based waveguide detector of a preset size.

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