Waveguide type avalanche photodetector based on buried heterojunction and preparation method thereof

Abstract

The invention provides a waveguide type avalanche photodetector based on a buried heterojunction and a preparation method thereof. The avalanche photodetector comprises a substrate structure, a waveguide structure and an upper layer structure, the substrate structure comprises a substrate and a barrier layer arranged on the substrate; the waveguide structure comprises a waveguide layer arranged on the barrier layer and an N-type transition layer arranged on the waveguide layer, the waveguide layer comprises a ridge waveguide, the transition layer comprises a conical structure, and the ridge waveguide is in contact with the conical structure; the upper layer structure comprises an avalanche photoelectric detection structure arranged on the N-type transition layer and a buried heterojunction epitaxial structure covering the avalanche photoelectric detection structure. According to the detector provided by the invention, the leakage current of the side wall of the mesa is limited by growing the buried heterojunction, and the possibility that dark current enters the multiplication layer to be amplified is reduced; incident light is transmitted through the waveguide and is coupled into the conical structure of the transition layer, and the conical structure plays a role in spot size conversion, so that the incident light is more effectively coupled into the absorption layer.

Description

Technical Field

[0001] The present application relates to the technical field of optoelectronic materials and devices, and in particular to a waveguide-type avalanche photodetector based on a buried heterojunction and a preparation method thereof. Background Art

[0002] Avalanche photodetectors are photoelectric chips that amplify photogenerated current by multiplying photogenerated carriers through the avalanche effect, thereby achieving applications such as long-distance reception, detection, or weak light detection. While the photogenerated current is amplified, the dark current may also be amplified, and the background noise of the dark current amplification greatly affects the detection accuracy of the detector. Therefore, limiting the dark current level is one of the development trends of avalanche photodetectors.

[0003] Dark current includes sidewall leakage current. In order to limit the sidewall leakage current, the existing technology usually adopts a passivation method of growing silicon oxide and silicon nitride insulating dielectric films on the sidewalls, or covering organic polymers such as BCB glue. With the development of technology, reducing the equivalent active area size of avalanche photodetectors is one of the keys to improving the bandwidth of optoelectronic chips. Although BCB glue has a low dielectric constant, as a negative glue, it has low lithography accuracy and is difficult to apply to devices with higher precision levels. Therefore, in pursuit of higher speed and higher precision avalanche photodetectors, it is necessary to find a passivation method that can effectively limit dark current and meet higher precision requirements. Summary of the invention

[0004] To solve the above problems, the present application provides a waveguide avalanche photodetector based on a buried heterojunction and a preparation method, which limits the lateral leakage current by burying the heterojunction, thereby significantly reducing the dark current level and can be applied to miniaturized optoelectronic chips with finer structures.

[0005] This application adopts the following technical solutions:

[0006] In a first aspect, a waveguide-type avalanche photodetector based on a buried heterojunction is provided, wherein the avalanche photodetector comprises: a substrate structure, a waveguide structure, and an upper structure; wherein:

[0007] The substrate structure includes: a substrate, and a barrier layer disposed on the substrate;

[0008] The waveguide structure includes: a waveguide layer disposed on the barrier layer, and an N-type transition layer disposed on the waveguide layer; the waveguide layer includes a ridge waveguide, the transition layer includes a cone structure, and the ridge waveguide is in contact with the cone structure;

[0009] The upper structure includes: an avalanche photoelectric detection structure arranged on the N-type transition layer, and a buried heterojunction epitaxial structure covering the avalanche photoelectric detection structure.

[0010] Optionally, the avalanche photodetection structure includes: an N-type contact layer, and a mesa-shaped inner layer structure; wherein,

[0011] The N-type contact layer is disposed on the N-type transition layer;

[0012] The mesa-shaped inner layer structure is arranged on a part of the upper surface of the N-type contact layer, and comprises: an absorption layer, an N-type gradual change layer, an N-type field control layer, and a multiplication layer arranged in sequence away from the N-type contact layer.

[0013] Optionally, the buried heterojunction epitaxial structure forms a mesa-shaped outer layer structure covering the avalanche photodetection structure, and the buried heterojunction epitaxial structure includes: a first P-type film layer, an N-type film layer, and a second P-type film layer; wherein,

[0014] The first P-type film layer is disposed on a portion of the upper surface of the N-type contact layer and covers the side surfaces of the absorption layer, the N-type graded layer, and the N-type field control layer;

[0015] The N-type film layer is disposed on the first P-type film layer and covers the side surface of the multiplication layer;

[0016] The second P-type film layer is disposed on the N-type film layer and covers the upper surface of the multiplication layer.

[0017] Optionally, the avalanche photodetector further includes: a passivation layer, a P-pole metal, and an N-pole metal; wherein,

[0018] The passivation layer covers the barrier layer, the waveguide structure except the cone-shaped structure and the ridge-shaped waveguide, and the side surface of the upper structure, and the passivation layer also covers the upper surface of the second P-type film layer;

[0019] The passivation layer forms a P-pole window on the upper surface of the second P-type film layer, and forms an N-pole window on the upper surface of the N-type contact layer where the mesa-shaped inner layer structure and the mesa-shaped outer layer structure are not provided;

[0020] The P-pole metal is arranged in the P-pole window;

[0021] The N-pole metal is arranged in the N-pole window.

[0022] Optionally, a waveguide end face anti-reflection film is provided on the side end face of the ridge waveguide.

[0023] Optionally, the substrate is a semi-insulating InP substrate;

[0024] The barrier layer is a semi-insulating InP barrier layer, and the thickness of the barrier layer is 0.3-1 μm.

[0025] Optionally, the waveguide layer is a semi-insulating InGaAsP waveguide layer, and the thickness of the waveguide layer is 0.3-1 μm;

[0026] The N-type transition layer is an nI nGaAsP transition layer, the thickness of the N-type transition layer is 0.05-0.2 μm, and the doping concentration is 1×10 17 ~5×10 17 cm -3 .

[0027] Optionally, the N-type contact layer is an nI nP contact layer, the thickness of the N-type contact layer is 0.3-1 μm, and the doping concentration is 1×10 18 ~3×10 18 cm -3 ;

[0028] The absorption layer is an iI nGaAs absorption layer, the thickness of the absorption layer is 0.2 to 3 μm, and the absorption layer is non-doped;

[0029] The N-type graded layer is an nI nGaAsP graded layer, the thickness of the N-type graded layer is 0.05-0.3 μm, and the doping concentration is 1×10 16 ~3×10 16 cm -3 ;

[0030] The N-type field control layer is an nI nP field control layer, the thickness of the N-type field control layer is 0.05-0.3 μm, and the doping concentration is 1×10 17 ~5×10 17 cm -3 ;

[0031] The multiplication layer is an iI nP multiplication layer, the thickness of the multiplication layer is 0.1-0.5 μm, and the multiplication layer is non-doped.

[0032] Optionally, the first P-type film layer is a first pI nP layer, the thickness of the first P-type film layer is 0.3-3.6 μm, and the doping concentration is 1×10 17 ~10×10 17 cm -3 ;

[0033] The N-type film layer is an nI nP layer, the thickness of the N-type film layer is 0.15-0.6 μm, and the doping concentration is 1×10 17 ~10×10 17 cm -3 ;

[0034] The second P-type film layer is a second pI nP layer, and the thickness of the second P-type film layer is 0.8-6 μm, and the doping concentration is 5×10 18 ~13×10 18 cm -3 .

[0035] In a second aspect, a method for preparing a waveguide avalanche photodetector based on a buried heterojunction is provided, comprising the following steps:

[0036] forming a substrate structure; wherein the substrate structure comprises: a substrate, and a barrier layer disposed on the substrate;

[0037] A waveguide structure is formed; wherein the waveguide structure comprises: a waveguide layer disposed on the barrier layer, and an N-type transition layer disposed on the waveguide layer; the waveguide layer comprises a ridge waveguide, the transition layer comprises a cone structure, and the ridge waveguide contacts the cone structure;

[0038] An upper structure is formed; wherein the upper structure includes: an avalanche photoelectric detection structure arranged on the N-type transition layer, and a buried heterojunction epitaxial structure covering the avalanche photoelectric detection structure.

[0039] Optionally, the method comprises the following steps:

[0040] Forming a basic structure; wherein the basic structure includes: a barrier layer, a waveguide layer, an N-type transition layer, an N-type contact layer, an absorption layer, an N-type graded layer, an N-type field control layer, and a multiplication layer grown sequentially on a substrate;

[0041] A first mesa structure is formed based on the basic structure; wherein the first mesa structure is formed on the absorption layer, the N-type graded layer, the N-type field control layer, and the multiplication layer;

[0042] A planar structure is formed based on the first terrace structure; wherein the planar structure includes: a first P-type film layer, an N-type film layer, and a second P-type film layer;

[0043] A second mesa structure is formed based on the planar structure; wherein the second mesa structure includes: a first substructure formed by a first P-type film layer, an N-type film layer, and a second P-type film layer, and a second substructure formed by an N-type contact layer;

[0044] A cone structure is formed in the N-type transition layer, and a ridge waveguide is formed in the waveguide layer;

[0045] A third mesa structure is formed; wherein the third mesa structure is formed in the waveguide layer other than the ridge waveguide, and the barrier layer.

[0046] Optionally, the method further includes:

[0047] Forming a passivation layer; wherein the passivation layer covers the barrier layer, the waveguide structure except the cone-shaped structure and the ridge-shaped waveguide, and the side surface of the upper structure, and the passivation layer also covers the upper surface of the second P-type film layer;

[0048] A P-pole window and an N-pole window are formed; wherein the P-pole window is formed in the passivation layer on the upper surface of the second P-type film layer, and the N-pole window is formed in the passivation layer on the upper surface of the N-type contact layer where the mesa-shaped inner layer structure and the mesa-shaped outer layer structure are not provided;

[0049] A P-pole metal is deposited in the P-pole window, and an N-pole metal is deposited in the N-pole window.

[0050] Optionally, the method further includes:

[0051] A waveguide end face anti-reflection film is formed; wherein the waveguide end face anti-reflection film is formed on the side end face of the ridge waveguide.

[0052] At least one of the above technical solutions adopted in this application can achieve the following beneficial effects:

[0053] The waveguide avalanche photodetector based on buried heterojunction provided in the present application limits the leakage current of the side wall of the table by growing a buried heterojunction, thereby reducing the possibility of dark current entering the multiplication layer for amplification. Compared with the common method of covering with BCB glue, the buried heterojunction can achieve sidewall passivation for finer structures. The waveguide avalanche photodetector based on buried heterojunction provided in the present application transmits the incident light through the waveguide and couples it into the conical structure of the upper layer. The conical structure plays the role of mode spot conversion, allowing the incident light to be more effectively coupled into the absorption layer, thereby avoiding the problem that fine structures are difficult to couple using conventional front or back photosensitive surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0055] Figure 1 A schematic structural diagram of a waveguide avalanche photodetector based on a buried heterojunction according to an embodiment of the present application is shown;

[0056] Figure 2 A schematic structural diagram of a waveguide avalanche photodetector based on a buried heterojunction according to another embodiment of the present application is shown;

[0057] Figure 3 A schematic flow chart showing a method for preparing a waveguide-type avalanche photodetector based on a buried heterojunction according to an embodiment of the present application;

[0058] Figure 4 A schematic flow chart showing a method for preparing a waveguide-type avalanche photodetector based on a buried heterojunction according to another embodiment of the present application;

[0059] Figure 5A schematic diagram showing a basic structure formed according to another embodiment of the present application;

[0060] Figure 6 A schematic diagram showing a first stage-type structure formed based on a basic structure according to another embodiment of the present application;

[0061] Figure 7 A schematic diagram showing a planar structure formed based on a first stage-type structure according to another embodiment of the present application;

[0062] Figure 8 A schematic diagram showing a second terrace structure formed based on a planar structure according to another embodiment of the present application;

[0063] Fig. 9 A schematic diagram showing a method of forming a tapered structure in an N-type transition layer and a ridge waveguide in a waveguide layer according to another embodiment of the present application is shown, wherein: Fig. 9 a is a schematic diagram of the first angle, Fig. 9 b is a schematic diagram of the second angle;

[0064] Fig.10 A schematic diagram showing the formation of a third terrace structure according to another embodiment of the present application;

[0065] Fig.11 A schematic flow chart of a method for preparing a waveguide-type avalanche photodetector based on a buried heterojunction according to another embodiment of the present application is shown;

[0066] Fig.12 A schematic diagram showing forming a passivation layer according to yet another embodiment of the present application;

[0067] Fig.13 A schematic diagram showing the formation of a P-pole window and an N-pole window according to yet another embodiment of the present application;

[0068] Fig.14 A schematic diagram showing deposition of a P-pole metal in a P-pole window and deposition of an N-pole metal in an N-pole window according to yet another embodiment of the present application is shown. DETAILED DESCRIPTION

[0069] The exemplary embodiments of the present application will be described in more detail below. However, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to enable the scope of the present application to be fully communicated to those skilled in the art.

[0070] The disclosure of the present invention provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described in the present invention. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0071] Generally, the terms may be understood at least in part based on the usage of the above invention. For example, the term "one or more" used in the present invention depends at least in part on the above invention, and may be used to describe any component, structure or feature in a singular form, or may be used to describe a combination of components, structures or features in a plural form. Similarly, terms such as "one", "an" or "the" may also be understood at least in part based on the above invention as conveying singular usage or conveying plural usage. In addition, the term "based on..." may be understood as not necessarily intended to convey a set of exclusive factors, but may alternatively, at least in part depending on the context, allow for the presence of additional factors that do not necessarily have to be explicitly described.

[0072] It should be noted that, in the description of the present application, the meanings of the terms "on", "over", "above", "over", etc. should be interpreted in the broadest way, meaning that the description containing these terms is interpreted as "the component can be set on another component in direct contact, or there can be intermediate components or layers between the components."

[0073] For ease of description, the present application may also use spatially relative terms such as "under", "beneath", "below", "under", "upper", "lower", etc. to describe the relationship of one component to another component shown in the drawings. In addition to the orientations described in the drawings, the spatially relative terms are also intended to cover different orientations of the device in use or operation. The device can be oriented in other ways, and the spatially relative descriptions used in the present application can be interpreted accordingly.

[0074] Figure 1 A schematic structural diagram of a waveguide avalanche photodetector based on a buried heterojunction proposed in one embodiment of the present application is shown.

[0075] Reference Figure 1 As shown, the buried heterojunction-based waveguide avalanche photodetector of this embodiment may include: a substrate structure 1 , a waveguide structure 2 , and an upper structure 3 .

[0076] The substrate structure 1 includes a substrate 11 and a barrier layer 12 disposed on the substrate 11 .

[0077] The waveguide structure 2 includes: a waveguide layer 21 disposed on the barrier layer 12 , and an N-type transition layer 22 disposed on the waveguide layer 21 ; the waveguide layer includes a ridge waveguide 23 , the transition layer 22 includes a tapered structure 24 , and the ridge waveguide 23 contacts the tapered structure 24 .

[0078] The upper structure 3 includes: an avalanche photodetection structure 31 disposed on the N-type transition layer 22 , and a buried heterojunction epitaxial structure 32 covering the avalanche photodetection structure 31 .

[0079] In some optional implementations, the avalanche photodetection structure 31 includes: an N-type contact layer 311 and a mesa-shaped inner layer structure 312 .

[0080] The N-type contact layer 311 is disposed on the N-type transition layer 22 .

[0081] The mesa-shaped inner layer structure 312 is disposed on a portion of the upper surface of the N-type contact layer 311 , and includes an absorption layer 3121 , an N-type graded layer 3122 , an N-type field control layer 3123 , and a multiplication layer 3124 , which are sequentially disposed away from the N-type contact layer 311 .

[0082] In some optional embodiments, the buried heterojunction epitaxial structure 32 forms a mesa-shaped outer layer structure covering the avalanche photodetection structure 31 , and the buried heterojunction epitaxial structure 32 includes: a first P-type film layer 321 , an N-type film layer 322 , and a second P-type film layer 323 .

[0083] The first P-type film layer 321 is disposed on a portion of the upper surface of the N-type contact layer 311 , and covers the side surfaces of the absorption layer 3121 , the N-type graded layer 3122 , and the N-type field control layer 3123 .

[0084] The N-type film layer 322 is disposed on the first P-type film layer 321 and covers the side surface of the multiplication layer 3124 .

[0085] The second P-type film layer 323 is disposed on the N-type film layer 322 and covers the upper surface of the multiplication layer 3124 .

[0086] The buried heterojunction-based waveguide avalanche photodetector structure provided in the embodiment of the present application includes, from bottom to top, a substrate 11, a barrier layer 12, a waveguide layer 21, an N-type transition layer 22, an N-type contact layer 311, a mesa-shaped inner layer structure 312, and a buried heterojunction epitaxial structure 32.

[0087] The substrate 11 may be a semi-insulating InP substrate.

[0088] The barrier layer 12 may be a semi-insulating InP barrier layer, and the thickness of the barrier layer 12 is 0.3-1 μm.

[0089] The waveguide layer 21 may be a semi-insulating InGaAsP waveguide layer, and the thickness of the waveguide layer 21 is 0.3-1 μm. A ridge waveguide 23 is formed at a certain thickness on the upper surface of the waveguide layer 21 .

[0090] The N-type transition layer 22 may be an nI nGaAsP transition layer. The thickness of the N-type transition layer 22 is 0.05 to 0.2 μm, and the doping concentration is 1×10 17 ~5×10 17 cm -3 A conical structure 24 with a certain inclination angle is formed on one side of the N-type transition layer 22 close to the ridge waveguide 23 , and the conical structure 24 is in contact with the ridge waveguide 23 .

[0091] The N-type contact layer 311 may be an nI nP contact layer. The thickness of the N-type contact layer 311 is 0.3-1 μm and the doping concentration is 1×10 18 ~3×10 18 cm -3 .

[0092] The mesa-shaped inner layer structure 312 is disposed on a portion of the upper surface of the N-type contact layer 311. The mesa-shaped inner layer structure 312 includes, from bottom to top, an absorption layer 3121, an N-type graded layer 3122, an N-type field control layer 3123, and a multiplication layer 3124.

[0093] The absorption layer 3121 may be an iInGaAs absorption layer, the thickness of the absorption layer 3121 is 0.2-3 μm, and the absorption layer 3121 is intrinsically undoped.

[0094] The N-type graded layer 3122 may be an nI nGaAsP graded layer. The thickness of the N-type graded layer 3122 is 0.05-0.3 μm, and the doping concentration is 1×10 16 ~3×10 16 cm -3 .

[0095] The N-type field control layer 3123 may be an nI nP field control layer. The thickness of the N-type field control layer 3123 is 0.05-0.3 μm, and the doping concentration is 1×10 17 ~5×10 17 cm -3 .

[0096] The multiplication layer 3124 may be an iI nP multiplication layer, the thickness of the multiplication layer 3124 is 0.1-0.5 μm, and the multiplication layer 3124 is intrinsically undoped.

[0097] The buried heterojunction epitaxial structure 32 covers the mesa inner layer structure 312 and is disposed on a portion of the upper surface of the N-type contact layer 311. The buried heterojunction epitaxial structure 32 includes, from bottom to top, a first P-type film layer 321, an N-type film layer 322, and a second P-type film layer 323.

[0098] The first P-type film layer 321 may be a first pI nP layer. The thickness of the first P-type film layer 321 is 0.3-3.6 μm, and the doping concentration is 1×10 17 ~10×10 17 cm -3 .

[0099] The N-type film layer 322 may be an nI nP layer. The thickness of the N-type film layer 322 is 0.15-0.6 μm, and the doping concentration is 1×10 17 ~10×10 17 cm -3 .

[0100] The second P-type film layer 323 may be a second pI nP layer. The thickness of the second P-type film layer 323 is 0.8-6 μm, and the doping concentration is 5×10 18 ~13×10 18 cm -3 .

[0101] Figure 2 A schematic structural diagram of a waveguide avalanche photodetector based on a buried heterojunction proposed in another embodiment of the present application is shown.

[0102] Reference Figure 2 As shown, the buried heterojunction-based waveguide avalanche photodetector of this embodiment may further include: a passivation layer 4 , a P-pole metal 5 , and an N-pole metal 6 .

[0103] The passivation layer 4 covers the barrier layer 12 , the waveguide structure 2 except the tapered structure 24 and the ridge waveguide 23 , and the side surface of the upper structure 3 . The passivation layer 4 also covers the upper surface of the second P-type film layer 323 .

[0104] The passivation layer 4 forms a P-pole window on the upper surface of the second P-type film layer 323 , and forms an N-pole window on the upper surface of the N-type contact layer 311 where the mesa-shaped inner layer structure 312 and the mesa-shaped outer layer structure are not provided.

[0105] The P-pole metal 5 is disposed in the P-pole window.

[0106] The N-pole metal 6 is disposed in the N-pole window.

[0107] In some optional implementations, a waveguide end face anti-reflection film 25 is provided on the side end face of the ridge waveguide 23 .

[0108] The waveguide end face anti-reflection film 25 can increase the transmittance of the end face of the ridge waveguide 23, thereby improving the light-intake efficiency of the avalanche photodetector.

[0109] That is, a waveguide avalanche photodetector based on a buried heterojunction proposed in another embodiment of the present application includes the following structure.

[0110] Semi-insulating InP substrate.

[0111] A semi-insulating InP barrier layer is disposed on the upper surface of the semi-insulating InP substrate.

[0112] The semi-insulating InP substrate and the semi-insulating InP barrier layer constitute a substrate structure.

[0113] A semi-insulating InGaAsP waveguide layer is disposed on the upper surface of the semi-insulating InP barrier layer. A certain thickness of the upper surface of the semi-insulating InGaAsP waveguide layer forms a ridge waveguide, and a waveguide end face anti-reflection film is disposed on the side end face of the ridge waveguide.

[0114] An nI nGaAsP transition layer is disposed on the upper surface of the semi-insulating I nGaAsP waveguide layer. The nI nGaAsP transition layer protrudes on one side close to the ridge waveguide to form a cone structure with a certain inclination angle, and the cone structure contacts the ridge waveguide.

[0115] The semi-insulating InGaAsP waveguide layer and the nI nGaAsP transition layer constitute a waveguide structure.

[0116] An nI nP contact layer is arranged on the upper surface of the nI nGaAsP transition layer.

[0117] A mesa-shaped inner layer structure is arranged on the upper surface of the nI nP contact layer. The mesa-shaped inner layer structure occupies part of the upper surface of the nI nP contact layer; the mesa-shaped inner layer structure is composed of an iI nGaAs absorption layer arranged on the upper surface of the nI nP contact layer, an nI nGaAsP graded-change layer arranged on the upper surface of the i-InGaAs absorption layer, an nI nP field control layer arranged on the upper surface of the nI nGaAsP graded-change layer, and an iI nP multiplication layer arranged on the upper surface of the nI nP field control layer.

[0118] A mesa-shaped outer layer structure is also arranged on the upper surface of the nI nP contact layer. The mesa-shaped outer layer structure occupies part of the upper surface of the nI nP contact layer; the mesa-shaped outer layer structure is composed of a first pI nP layer arranged on the upper surface of the nI nP contact layer and covering the side surfaces of the iI nGaAs absorption layer, the n-InGaAsP graded layer, and the nI nP field control layer, an nI nP layer arranged on the upper surface of the first pI nP layer and covering the side surface of the iI nP multiplication layer, and a second pI nP layer arranged on the upper surface of the nI nP layer and covering the upper surface of the iI nP multiplication layer.

[0119] The nI nP contact layer, the mesa-shaped inner layer structure, and the mesa-shaped outer layer structure constitute the upper structure.

[0120] A passivation layer is disposed on side surfaces of the semi-insulating InP barrier layer, the waveguide structure except the tapered structure and the ridge waveguide, and the upper structure, and an upper surface of the second pI nP layer.

[0121] A P-pole window is formed on the upper surface of the second pI nP layer, and an N-pole window is formed on the upper surface of the nI nP contact layer where the mesa-shaped inner layer structure and the mesa-shaped outer layer structure are not provided.

[0122] An N-pole metal is disposed in the N-pole window.

[0123] A P-pole metal is disposed in the P-pole window.

[0124] Figure 3 The flowchart of the method for preparing a waveguide avalanche photodetector based on a buried heterojunction according to one embodiment of the present application is shown. Figure 3 As shown, the method for preparing the waveguide avalanche photodetector based on the buried heterojunction proposed in this embodiment includes the following steps:

[0125] S101, forming a substrate structure; wherein the substrate structure includes: a substrate, and a barrier layer disposed on the substrate;

[0126] S102, forming a waveguide structure; wherein the waveguide structure comprises: a waveguide layer disposed on the barrier layer, and an N-type transition layer disposed on the waveguide layer; the waveguide layer comprises a ridge waveguide, the transition layer comprises a cone structure, and the ridge waveguide is in contact with the cone structure;

[0127] S103, forming an upper structure; wherein the upper structure includes: an avalanche photoelectric detection structure disposed on the N-type transition layer, and a buried heterojunction epitaxial structure covering the avalanche photoelectric detection structure.

[0128] Figure 4 FIG. 1 is a flow chart showing a method for preparing a waveguide-type avalanche photodetector based on a buried heterojunction according to another embodiment of the present application. Figure 4 As shown, the method for preparing the waveguide avalanche photodetector based on the buried heterojunction proposed in this embodiment includes the following steps:

[0129] S201, forming a basic structure; wherein the basic structure includes: a barrier layer, a waveguide layer, an N-type transition layer, an N-type contact layer, an absorption layer, an N-type graded layer, an N-type field control layer, and a multiplication layer grown sequentially on a substrate.

[0130] In some optional embodiments, forming a base structure includes: using organic metal chemical vapor deposition to sequentially grow a barrier layer, a waveguide layer, an N-type transition layer, an N-type contact layer, an absorption layer, an N-type graded layer, an N-type field control layer, and a multiplication layer on a substrate.

[0131] Figure 5 A schematic diagram of forming the base structure is shown.

[0132] Specifically, a barrier layer 12 , a waveguide layer 21 , an N-type transition layer 22 , an N-type contact layer 311 , an absorption layer 3121 , an N-type graded layer 3122 , an N-type field control layer 3123 , and a multiplication layer 3124 may be sequentially grown on a substrate 11 by metal organic chemical vapor deposition (MOCVD).

[0133] S202, forming a first mesa structure based on the basic structure; wherein the first mesa structure is formed on the absorption layer, the N-type graded layer, the N-type field control layer, and the multiplication layer.

[0134] In some optional embodiments, a first mesa structure is formed based on the basic structure, including: depositing a first mask layer, etching the first mask layer to form a first mask pattern on the upper surface of the multiplication layer; corroding the absorption layer, the N-type gradual change layer, the N-type field control layer, and the multiplication layer using a bromine solution according to the first mask pattern to form a first mesa structure.

[0135] Figure 6 A schematic diagram showing the formation of a first terrace structure based on a basic structure is shown.

[0136] Specifically, the first mesa structure can be formed by wet etching, photolithography, and dry etching. First, deposit the first mask layer, which can be a SiO2 thin film, spin-coat the photoresist, and use a photolithography machine to expose and develop to obtain the first target pattern. Next, use dry etching to remove part of the first mask layer to obtain the first mask pattern formed on the upper surface of the multiplication layer. Then, remove the photoresist, and use a bromine solution of a certain concentration to etch the absorption layer 3121, the N-type gradual change layer 3122, the N-type field control layer 3123, and the multiplication layer 3124 according to the first mask pattern, so as to obtain the first mesa structure. Finally, remove the first mask pattern.

[0137] In addition, in some cases, the formed basic structure may further include a cap layer grown on the multiplication layer, which serves as an anti-oxidation protection layer to protect other basic structure parts. The cap layer may be an iInGaAs cap layer, and the thickness of the cap layer is 0.05-0.15 μm.

[0138] When the base structure includes a cap layer, in the step of forming the first terrace structure based on the base structure, the cap layer needs to be removed first, and a sulfuric acid solution of a certain concentration can be used to remove the cap layer.

[0139] S203, forming a planar structure based on the first terrace structure; wherein the planar structure includes: a first P-type film layer, an N-type film layer, and a second P-type film layer.

[0140] In some optional embodiments, a planar structure is formed based on the first terrace structure, including: depositing a second mask layer, etching the second mask layer to form a second mask pattern on the upper surface of the multiplication layer; growing a first P-type film layer on the N-type contact layer 311 by using an organic metal chemical vapor deposition method, so that the first P-type film layer covers the side surfaces of the absorption layer, the N-type gradual change layer, and the N-type field control layer; growing an N-type film layer on the first P-type film layer by using an organic metal chemical vapor deposition method, so that the N-type film layer covers the side surface of the multiplication layer; removing the second mask pattern by using a buffered oxide etchant; and growing a second P-type film layer on the multiplication layer and the N-type film layer by using an organic metal chemical vapor deposition method to form a planar structure.

[0141] Figure 7 A schematic diagram showing a planar structure formed based on the first terrace structure.

[0142] Specifically, a planar structure can be formed by processes such as metal organic chemical vapor deposition (MOCVD) and wet etching. First, a second mask layer is deposited, and the second mask layer can be a SiO2 film. A photoresist is spin-coated, and a second target pattern is obtained by exposure using a photolithography machine and development. A portion of the second mask layer is removed by dry etching to obtain a second mask pattern formed on the upper surface of the multiplication layer. Secondly, a first P-type film layer 321 is grown on the N-type contact layer 311 by using an organic metal chemical vapor deposition method (MOCVD), so that the maximum thickness of the first P-type film layer 321 reaches the bottom of the multiplication layer 3124. Next, an N-type film layer 322 is grown on the first P-type film layer 321 by using an organic metal chemical vapor deposition method (MOCVD), so that the maximum thickness of the N-type film layer 322 reaches the top of the multiplication layer 3124. Then, the second mask pattern is removed by using a buffered oxide etching solution (BOE solution). Finally, a second P-type film layer 323 is grown on the multiplication layer 3124 and the N-type film layer 322 by using a metal organic chemical vapor deposition method (MOCVD) to obtain a planar structure.

[0143] In addition, in some cases, in the step of forming the first mesa structure based on the base structure, when the first mask pattern is appropriate, the first mask pattern may not be removed, that is, after obtaining the first mesa structure, the first mask pattern is retained, and the step of forming the planar structure based on the first mesa structure is entered.

[0144] In this case, in the step of forming a planar structure based on the first mesa structure, the second mask layer is no longer deposited, and the second mask layer does not need to be etched to form a second mask pattern on the upper surface of the multiplication layer. That is, the first mask pattern is used as the second mask pattern.

[0145] S204, forming a second mesa structure based on the planar structure; wherein the second mesa structure includes: a first substructure formed by a first P-type film layer, an N-type film layer, and a second P-type film layer, and a second substructure formed by an N-type contact layer.

[0146] In some optional embodiments, a second terrace structure is formed, including: depositing a third mask layer, etching the third mask layer to form a third mask pattern on the upper surface of the second P-type film layer, corroding the first P-type film layer, the N-type film layer, and the second P-type film layer with a bromine solution according to the third mask pattern to form a first substructure, wherein the first substructure exposes a portion of the upper surface of the N-type contact layer; removing the third mask pattern with a buffered oxide etchant; spin coating photoresist, exposing and developing with a photolithography machine to obtain a window exposing an edge of the N-type contact layer, corroding the N-type contact layer with a hydrochloric acid solution based on the window, and then removing the photoresist to form a second substructure.

[0147] Figure 8 A schematic diagram showing the formation of a second mesa structure based on a planar structure.

[0148] Specifically, the second mesa structure can be formed by processes such as photolithography, dry etching, and wet etching. First, a hard mask is used to deposit a third mask layer, which can be a SiO2 film, and a photoresist is spin-coated. After exposure using a photolithography machine, the third target pattern is obtained by developing. After removing part of the third mask layer by dry etching, a third mask pattern formed on the upper surface of the second P-type film layer 323 is obtained. The photoresist is removed, and a bromine solution is used to etch the first P-type film layer 321, the N-type film layer 322, and the second P-type film layer 323, thereby forming a first substructure and exposing the N-type contact layer 311. Secondly, the third mask pattern is removed by using a buffered oxide etching solution (BOE solution). Then, the photoresist is spin-coated, and after exposure using a photolithography machine, a window exposing the edge of the N-type contact layer 311 is obtained. A hydrochloric acid solution of a certain concentration is used to etch the exposed edge of the N-type contact layer 311, and the etching stops when the etching stop layer (N-type transition layer 22) is etched, and the photoresist is removed to obtain the second substructure.

[0149] S205, forming a cone structure in the N-type transition layer, and forming a ridge waveguide in the waveguide layer.

[0150] In some optional embodiments, a conical structure is formed in the N-type transition layer, and a ridge waveguide is formed in the waveguide layer, including: spin-coating photoresist, using a photolithography machine to gradually expose and develop, using dry etching to gradually etch the N-type transition layer to produce a target inclined conical structure; removing the photoresist; depositing a fourth mask layer, etching the fourth mask layer to form a fourth mask pattern on the upper surface of the waveguide layer, using dry etching to etch the waveguide layer according to the fourth mask pattern, and stopping after reaching a target waveguide thickness; using a buffered oxide etching solution to remove the fourth mask pattern to form a ridge waveguide.

[0151] Fig. 9 A schematic diagram showing a tapered structure formed in an N-type transition layer and a ridge waveguide formed in a waveguide layer is shown, wherein: Fig. 9 a is a schematic diagram of the first angle, Fig. 9 b is a schematic diagram of a second angle, where the second angle is the first angle rotated 90°.

[0152] Specifically, the conical structure and the ridge waveguide can be manufactured by processes such as photolithography and dry etching. First, the photoresist is spin-coated, and after exposure and development in different regions and steps using a photolithography machine, the N-type transition layer 22 is gradually etched using dry etching to manufacture the target inclined conical structure 24, and the N-type transition layer 22 forming the conical structure 24 exposes part of the upper surface of the waveguide layer 22, and the residual photoresist is removed. Secondly, the fourth mask layer is deposited, and the fourth mask layer can be a SiO2 thin film, and the photoresist is spin-coated, and after exposure and development using a photolithography machine, the fourth target pattern is obtained, and the fourth mask layer is removed by dry etching to obtain the fourth mask pattern formed on the upper surface of the waveguide layer 22, and then the waveguide layer 22 is processed by dry etching, and the etching is stopped after the target waveguide thickness is reached. Finally, the fourth mask pattern is removed using a buffered oxide etching solution (BOE solution), and the ridge waveguide 23 is obtained.

[0153] Step S206, forming a third mesa structure; wherein the third mesa structure is formed on the waveguide layer other than the ridge waveguide, and the barrier layer.

[0154] In some optional embodiments, forming a third mesa-type structure includes: depositing a fifth mask layer, etching the fifth mask layer to form a fifth mask pattern on the upper surface of the waveguide layer, the fifth mask pattern exposing the edge of the waveguide layer except the ridge waveguide; and dry etching the waveguide layer except the ridge waveguide and the barrier layer according to the fifth mask pattern to form the third mesa-type structure.

[0155] Fig.10 A schematic diagram showing the formation of a third terrace structure is shown.

[0156] Specifically, the third mesa structure can be formed by photolithography and dry etching. First, a fifth mask layer is deposited, which may be a SiO2 thin film, and a photoresist is spin-coated. A fifth target pattern is obtained by exposure and development using a photolithography machine. A portion of the fifth mask layer is removed by dry etching to obtain a fifth mask pattern formed on the upper surface of the waveguide layer 21. The fifth mask pattern exposes the edge of the waveguide layer 21 except for the ridge waveguide 23, and the photoresist is removed. Next, dry etching is performed starting from the waveguide layer 21 until the stop layer (substrate 11) is reached, and the fifth mask pattern is removed by a buffered oxide etching solution (BOE solution) to obtain a third mesa structure.

[0157] in addition, Fig.11 A schematic flow chart of a method for preparing a waveguide-type avalanche photodetector based on a buried heterojunction according to another embodiment of the present application is shown. Fig.11 As shown, the method for preparing a waveguide avalanche photodetector based on a buried heterojunction may further include the following steps:

[0158] Step S207, forming a passivation layer; wherein the passivation layer covers the barrier layer, the waveguide structure except the cone-type structure and the ridge-type waveguide, and the side surface of the upper structure, and the passivation layer also covers the upper surface of the second P-type film layer.

[0159] In some optional embodiments, a passivation layer is formed, including: growing a silicon oxide and silicon nitride composite passivation film on the barrier layer, the waveguide structure other than the conical structure and the ridge waveguide, the side surface of the upper structure, and the upper surface of the second P-type film layer to form a passivation layer.

[0160] Fig.12 A schematic diagram of forming a passivation layer is shown.

[0161] Specifically, a silicon oxide and silicon nitride composite passivation film is grown on the barrier layer 12 , the waveguide structure 2 except the conical structure 24 and the ridge waveguide 23 , the side surfaces of the upper structure 3 , and the upper surface of the second P-type film layer 323 to form a passivation layer 4 .

[0162] Step S208, forming a P-pole window and an N-pole window; wherein the P-pole window is formed in the passivation layer on the upper surface of the second P-type film layer, and the N-pole window is formed in the passivation layer on the upper surface of the N-type contact layer without the mesa-shaped inner layer structure and the mesa-shaped outer layer structure.

[0163] In some optional embodiments, a P-pole window and an N-pole window are formed, including: spin coating photoresist, using a photolithography machine to expose and then develop to obtain a pattern of exposed electrode windows, wherein the pattern is a pattern of exposed P-pole window and exposed N-pole window; using dry etching to remove the passivation layer according to the pattern to form a P-pole window and an N-pole window; and removing the photoresist.

[0164] Fig.13 A schematic diagram of forming a P-pole window and an N-pole window is shown.

[0165] Specifically, the P-pole window and the N-pole window can be formed by photolithography and dry etching. First,

[0166] The photoresist is spin-coated, exposed using a photolithography machine, and then developed to obtain a pattern that exposes the electrode window. Next, the exposed passivation layer 4 is removed using dry etching according to the pattern to form corresponding P-pole windows and N-pole windows. Finally, the photoresist is removed.

[0167] Step S209, depositing a P-pole metal in the P-pole window and depositing an N-pole metal in the N-pole window.

[0168] In some optional embodiments, a P-pole metal is deposited in the P-pole window and an N-pole metal is deposited in the N-pole window, including: using thermal evaporation deposition to deposit a P-pole metal in the P-pole window and an N-pole metal in the N-pole window; and using chemical mechanical polishing to thin to a preset thickness.

[0169] Fig.14 A schematic diagram showing the deposition of P-pole metal in the P-pole window and the deposition of N-pole metal in the N-pole window is shown.

[0170] Specifically, it can be achieved by metal deposition. First, a thermal evaporation deposition method in physical vapor deposition (PVD) is used to deposit a P-pole metal 5 in the P-pole window and an N-pole metal 6 in the N-pole window. Then, the wafer is thinned to a preset thickness using chemical mechanical polishing (CMP) and then cleaved.

[0171] In addition, the method for preparing a waveguide avalanche photodetector based on a buried heterojunction may further include the following steps:

[0172] Step S210, forming a waveguide end face anti-reflection film; wherein the waveguide end face anti-reflection film is formed on the side end face of the ridge waveguide.

[0173] In some optional embodiments, forming a waveguide end face anti-reflection film includes: depositing the waveguide end face anti-reflection film on a side end face of a ridge waveguide.

[0174] The schematic diagram of forming the anti-reflection film on the waveguide end face is as follows Figure 2 shown.

[0175] Specifically, a waveguide end face anti-reflection film 25 is deposited on the side end face of the ridge waveguide 23 to increase the transmittance of the end face waveguide and improve the light entry efficiency of the detector.

[0176] The above is only a specific implementation of the present application. Under the above teachings of the present application, those skilled in the art can make other improvements or modifications based on the above embodiments. Those skilled in the art should understand that the above specific description is only to better explain the purpose of the present application, and the protection scope of the present application shall be based on the protection scope of the claims.

[0177] In addition, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims below, any one of the claimed embodiments may be used in any combination.

Claims

1. A waveguide avalanche photodetector based on a buried heterojunction, characterized in that: The avalanche photodetector comprises: a substrate structure, a waveguide structure, and an upper structure; wherein, The substrate structure comprises: a substrate, and a barrier layer disposed on the substrate; The waveguide structure comprises: a waveguide layer disposed on the barrier layer, and an N-type transition layer disposed on the waveguide layer; the waveguide layer comprises a ridge waveguide, the transition layer comprises a tapered structure, and the ridge waveguide contacts the tapered structure; The upper structure includes: an avalanche photoelectric detection structure arranged on the N-type transition layer, and a buried heterojunction epitaxial structure covering the avalanche photoelectric detection structure.

2. The buried heterojunction-based waveguide avalanche photodetector according to claim 1, characterized in that: The avalanche photoelectric detection structure includes: an N-type contact layer and a mesa-shaped inner layer structure; wherein, The N-type contact layer is disposed on the N-type transition layer; The mesa-shaped inner layer structure is arranged on a part of the upper surface of the N-type contact layer, and comprises: an absorption layer, an N-type graded layer, an N-type field control layer, and a multiplication layer arranged in sequence away from the N-type contact layer.

3. The buried heterojunction-based waveguide avalanche photodetector according to claim 2, characterized in that: The buried heterojunction epitaxial structure forms a mesa-shaped outer layer structure covering the avalanche photodetection structure, and the buried heterojunction epitaxial structure includes: a first P-type film layer, an N-type film layer, and a second P-type film layer; wherein, The first P-type film layer is disposed on a portion of the upper surface of the N-type contact layer and covers the absorption layer, the N-type graded layer, and the side surfaces of the N-type field control layer; The N-type film layer is disposed on the first P-type film layer and covers the side surface of the multiplication layer; The second P-type film layer is disposed on the N-type film layer and covers the upper surface of the multiplication layer.

4. The buried heterojunction-based waveguide avalanche photodetector according to claim 3, characterized in that: The avalanche photodetector further includes: a passivation layer, a P-pole metal, and an N-pole metal; wherein, The passivation layer covers the barrier layer, the waveguide structure except the tapered structure and the ridge waveguide, and the side surface of the upper structure, and the passivation layer also covers the upper surface of the second P-type film layer; The passivation layer forms a P-pole window on the upper surface of the second P-type film layer, and forms an N-pole window on the upper surface of the N-type contact layer where the mesa-shaped inner layer structure and the mesa-shaped outer layer structure are not provided; The P-pole metal is arranged in the P-pole window; The N-pole metal is disposed in the N-pole window.

5. The buried heterojunction-based waveguide avalanche photodetector according to claim 1, characterized in that: The side end face of the ridge waveguide is provided with a waveguide end face anti-reflection film.

6. The buried heterojunction-based waveguide avalanche photodetector according to claim 1, characterized in that: The substrate is a semi-insulating InP substrate; The barrier layer is a semi-insulating InP barrier layer, and the thickness of the barrier layer is 0.3-1 μm.

7. The buried heterojunction-based waveguide avalanche photodetector according to claim 1, characterized in that: The waveguide layer is a semi-insulating InGaAsP waveguide layer, and the thickness of the waveguide layer is 0.3-1 μm; The N-type transition layer is an n-InGaAsP transition layer, the thickness of the N-type transition layer is 0.05-0.2 μm, and the doping concentration is 1×10 17 ~5×10 17 cm -3 .

8. The buried heterojunction-based waveguide avalanche photodetector according to claim 2, characterized in that: The N-type contact layer is an n-InP contact layer, the thickness of the N-type contact layer is 0.3-1 μm, and the doping concentration is 1×10 18 ~3×10 18 cm -3 ; The absorption layer is an i-InGaAs absorption layer, the thickness of the absorption layer is 0.2-3 μm, and the absorption layer is non-doped; The N-type graded layer is an n-InGaAsP graded layer, the thickness of the N-type graded layer is 0.05-0.3 μm, and the doping concentration is 1×10 16 ~3×10 16 cm -3 ; The N-type field control layer is an n-InP field control layer, and the thickness of the N-type field control layer is 0.05-0.3 μm, and the doping concentration is 1×10 17 ~5×10 17 cm -3 ; The multiplication layer is an i-InP multiplication layer, the thickness of the multiplication layer is 0.1-0.5 μm, and the multiplication layer is non-doped.

9. The buried heterojunction-based waveguide avalanche photodetector according to claim 3, characterized in that: The first P-type film layer is a first p-InP layer, the thickness of the first P-type film layer is 0.3 to 3.6 μm, and the doping concentration is 1×10 17 ~10×10 17 cm -3 ; The N-type film layer is an n-InP layer, the thickness of the N-type film layer is 0.15-0.6 μm, and the doping concentration is 1×10 17 ~10×10 17 cm -3 ; The second P-type film layer is a second p-InP layer, the thickness of the second P-type film layer is 0.8 to 6 μm, and the doping concentration is 5×10 18 ~13×10 18 cm -3 .

10. A method for preparing a waveguide avalanche photodetector based on a buried heterojunction, characterized in that: The following steps are involved: forming a substrate structure; wherein the substrate structure comprises: a substrate, and a barrier layer disposed on the substrate; forming a waveguide structure; wherein the waveguide structure comprises: a waveguide layer disposed on the barrier layer, and an N-type transition layer disposed on the waveguide layer; the waveguide layer comprises a ridge waveguide, the transition layer comprises a tapered structure, and the ridge waveguide contacts the tapered structure; An upper structure is formed; wherein the upper structure includes: an avalanche photoelectric detection structure arranged on the N-type transition layer, and a buried heterojunction epitaxial structure covering the avalanche photoelectric detection structure.

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