CN116469944A - Class II superlattice photoelectric detector and manufacturing method thereof - Google Patents

Abstract

The application relates to the technical field of infrared detection, and discloses a II-type superlattice photoelectric detector and a manufacturing method thereof, wherein the II-type superlattice photoelectric detector comprises the following components: a substrate layer, a DBR reflection layer and a UTC structure sequentially positioned on the substrate layer; the UTC structure includes a bottom contact layer, a drift layer, an absorber layer, a barrier layer, and a top contact layer, which are stacked. In the UTC structure, the photon-generated carriers are excited in the unconsumed absorption layer, and only electrons are injected into the drift layer, so that the photon-generated carrier transmission time of the device is shortened, and the response speed of the device is improved; the DBR reflection layer and air are combined to form a resonator structure, light penetrating through the absorption layer can be reflected back to the absorption layer, light absorption of the device is increased, the DBR reflection layer is flexible in design and applicable to different wave bands, design flexibility of the device is improved, thickness of the absorption layer can be properly reduced under the condition of meeting high enough light absorption, dark current of the device is reduced, and photoelectric performance of the device is improved.

Description

A type II superlattice photodetector and its manufacturing method

technical field

The invention relates to the technical field of infrared detection, in particular to a type II superlattice photodetector and a manufacturing method thereof.

Background technique

Infrared detectors are devices that convert incident infrared radiation signals into electrical signals. Infrared detectors are mainly divided into two categories: heat-sensitive infrared detectors made by using the thermal effect of infrared radiation on objects and photoelectric infrared detectors made by using the photoelectric effect of semiconductors. At present, the technology of photodetector is the most mature. High-performance photoelectric infrared detectors mainly include mercury cadmium telluride infrared detectors, quantum well infrared detectors, quantum dot infrared detectors, type-II superlattice (type-II superlattice, T2SL) infrared detectors, etc. Type II superlattice materials are regarded as a substitute for mercury cadmium telluride (HgCdTe) infrared materials because of their large effective mass, suppression of Auger recombination, adjustable band gap, and large wavelength coverage. Among them, gallium (Ga)-free indium arsenide/indium arsenide antimony ₍ InAs/InAsSb) type II superlattice has become a general-purpose infrared photodetector material in recent years.

In recent years, the demand for high-speed mid-wave band infrared photodetectors has grown rapidly in various fields such as free-space optical communications and frequency-comb spectrometers. However, the commonly used PIN structure and nBn structure of type II superlattice photodetectors cannot meet the needs of fast detection, and have defects such as high dark current and low light absorption efficiency.

Therefore, how to solve the problems of low response speed and high dark current of type II superlattice photodetectors is a technical problem to be solved urgently by those skilled in the art.

Contents of the invention

In view of this, the object of the present invention is to provide a type II superlattice photodetector and its manufacturing method, which can shorten the photogenerated carrier transmission time of the device, improve the response speed and light absorption efficiency of the device, reduce the dark current of the device, and have high design flexibility at the same time. The specific plan is as follows:

A type II superlattice photodetector, comprising: a substrate layer, a DBR reflection layer and a UTC structure sequentially positioned on the substrate layer;

The UTC structure includes a bottom contact layer, a drift layer, an absorption layer, a barrier layer and a top contact layer which are stacked.

Preferably, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, the patterns of the top contact layer, the barrier layer, the absorption layer and the drift layer form the first mesa of the type II superlattice photodetector;

The patterns of the bottom contact layer and the DBR reflective layer form a second mesa of the type II superlattice photodetector; the second mesa is larger than the first mesa.

Preferably, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, it also includes:

A passivation layer on the first mesa surface and the second mesa surface.

Preferably, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, it also includes:

A metal electrode layer located on both sides of the upper surface of the first mesa and on both sides of the upper surface of the second mesa and in contact with the passivation layer.

Preferably, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, it also includes:

A buffer layer located between the substrate layer and the DBR reflective layer.

Preferably, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, the bottom contact layer is an n-type doped bottom contact layer;

The drift layer is an unintentionally doped drift layer;

The absorbing layer is a multi-layer absorbing layer whose p-type doping concentration gradually decreases along the direction from the top contact layer to the bottom contact layer;

The barrier layer is a p-type doped barrier layer;

The top contact layer is a p-type doped top contact layer.

The embodiment of the present invention also provides a method for manufacturing the above-mentioned type II superlattice photodetector as provided in the embodiment of the present invention, including:

forming a DBR reflective layer on the substrate layer;

A UTC structure is formed on the DBR reflective layer, which consists of a bottom contact layer, a drift layer, an absorption layer, a barrier layer and a top contact layer in sequence.

Preferably, in the manufacturing method of the above-mentioned type II superlattice photodetector provided in the embodiment of the present invention, it also includes:

performing a patterning process on the top contact layer, the barrier layer, the absorber layer and the drift layer to form a first mesa;

A patterning process is performed on the bottom contact layer and the DBR reflective layer to form a second mesa; the second mesa is larger than the first mesa.

Preferably, in the manufacturing method of the above-mentioned type II superlattice photodetector provided in the embodiment of the present invention, it also includes:

depositing a passivation layer material on the surfaces of the first mesa and the second mesa;

performing a patterning process on the passivation layer material to form a passivation layer pattern with a diffusion window;

A metal electrode layer is formed on the first mesa and the second mesa where the diffusion window is formed; the metal electrode layer is located on both sides of the upper surface of the first mesa and on both sides of the upper surface of the second mesa and is in contact with the passivation layer.

Preferably, in the manufacturing method of the above-mentioned type II superlattice photodetector provided in the embodiment of the present invention, a DBR reflective layer is formed on the substrate layer, including:

A buffer layer is formed on the substrate layer, and a DBR reflective layer is formed on the buffer layer.

As can be seen from the foregoing technical solutions, a type II superlattice photodetector provided by the present invention includes: a substrate layer, a DBR reflection layer and a UTC structure positioned on the substrate layer in turn; the UTC structure includes a stacked bottom contact layer, a drift layer, an absorption layer, a barrier layer and a top contact layer.

The above-mentioned type II superlattice photodetector provided by the present invention is designed with a combined structure of UTC structure and DBR reflective layer. In the UTC structure, photogenerated carriers are excited in the unexhausted absorbing layer, and only electrons are injected into the drift layer, which shortens the photogenerated carrier transmission time of the device and improves the response speed of the device; the DBR reflective layer is combined with air to form a resonator structure, which can reflect the light penetrating through the absorbing layer back to the absorbing layer, increasing the light absorption of the device, and the design of the DBR reflective layer is flexible and suitable for different applications. The wavelength band improves the design flexibility of the device, and the thickness of the absorbing layer can be appropriately reduced when sufficient light absorption is satisfied, thereby reducing the dark current of the device and improving the photoelectric performance of the device.

In addition, the present invention also provides a corresponding manufacturing method for the type II superlattice photodetector, which further makes the above-mentioned type II superlattice photodetector more practical, and the manufacturing method has corresponding advantages.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following will briefly introduce the accompanying drawings that need to be used in the descriptions of the embodiments or related technologies. Obviously, the accompanying drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to the provided drawings without creative work.

Fig. 1 is one of the structural representations of the class II superlattice photodetector provided by the embodiment of the present invention;

Fig. 2 is the second structural schematic diagram of the class II superlattice photodetector provided by the embodiment of the present invention;

Fig. 3 is the flow chart of the manufacturing method of the class II superlattice photodetector provided by the embodiment of the present invention;

FIG. 4 is a schematic structural diagram obtained after performing step 1 of the manufacturing method of the class II superlattice photodetector provided by the embodiment of the present invention;

Fig. 5 is a structural schematic diagram obtained after performing step 2 of the manufacturing method of the type II superlattice photodetector provided by the embodiment of the present invention;

Fig. 6 is a structural schematic diagram obtained after performing step 3 of the manufacturing method of the type II superlattice photodetector provided by the embodiment of the present invention;

Fig. 7 is a structural schematic diagram obtained after performing step 4 of the manufacturing method of the type II superlattice photodetector provided by the embodiment of the present invention;

Fig. 8 is a structural schematic diagram obtained after performing step 5 of the manufacturing method of the type II superlattice photodetector provided by the embodiment of the present invention;

Fig. 9 is a structural schematic diagram obtained after performing step six of the manufacturing method of the type II superlattice photodetector provided by the embodiment of the present invention;

Among them, 1 is the substrate layer, 2 is the DBR reflection layer, 3 is the bottom contact layer, 4 is the drift layer, 5 is the absorption layer, 6 is the barrier layer, 7 is the top contact layer, 8 is the passivation layer, 9 is the metal electrode layer, and 10 is the buffer layer.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The present invention provides a class II superlattice photodetector, as shown in Figure 1, comprising: a substrate layer 1, a DBR (distributed Bragg reflector, distributed Bragg reflector) reflection layer 2 and a UTC (Uni-Traveling Carrier, single transport carrier) structure positioned on the substrate layer 1 in turn;

The UTC structure includes a bottom contact layer 3 , a drift layer 4 , an absorption layer 5 , a barrier layer 6 and a top contact layer 7 which are stacked.

In the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, a structure combining the UTC structure and the DBR reflective layer 2 is designed. In the UTC structure, photo-generated carriers are excited in the unexhausted absorber layer 5, and only electrons are injected into the drift layer 4, which shortens the photo-generated carrier transmission time of the device and improves the response speed of the device; the DBR reflective layer 2 is combined with air to form a resonator structure, which can reflect the light penetrating through the absorber layer 5 back to the absorber layer 5, increasing the light absorption of the device, and The design of the DBR reflective layer 2 is flexible, suitable for different wavelength bands, and improves the design flexibility of the device. Under the condition of satisfying high enough light absorption, the thickness of the absorbing layer 5 can be appropriately reduced, thereby reducing the dark current of the device and improving the photoelectric performance of the device.

It should be noted that, compared with the traditional photodetector structure, the type II superlattice photodetector combined with UTC and DBR provided by the embodiment of the present invention has the following outstanding advantages:

Since the photogenerated carriers of the UTC structure photodetector are excited in the undepleted absorbing layer and only electrons are injected into the drift layer, the effective carrier transit time of the type II superlattice photodetector with the UTC structure is shorter than that of a properly designed PIN structure, which is more suitable for free-space optical communication and frequency comb spectrometer and other fields, and is expected to be applied in the field of optical computing.

Add a DBR reflector to form a resonant cavity. You can choose a variety of material combinations, calculate the refractive index of the material through an interpolation algorithm, choose a combination of large and small refractive indices, and calculate the corresponding material combination parameters in the target band through the Fresnel formula combined with the transmission matrix. The design flexibility is high.

Compared with the traditional photodetector structure, the type II superlattice photodetector with DBR reflector has stronger light absorption ability, lower dark current and higher photoelectric performance.

Further, in specific implementation, in the above-mentioned class II superlattice photodetector provided by the embodiment of the present invention, as shown in Figure 1, the top contact layer 7, the barrier layer 6, the absorption layer 5 and the drift layer 4 can form the first mesa of the class II superlattice photodetector; the patterns of the bottom contact layer 3 and the DBR reflective layer 2 can form the second mesa of the class II superlattice photodetector; the second mesa is larger than the first mesa. Such mesa type II superlattice photodetectors have better performance.

It should be noted that the substrate layer 1 is located at the bottom and has the largest area, that is, the substrate layer 1 is larger than the second mesa, and the second mesa is larger than the first mesa, forming a stepped structure. In the process of making the first mesa and the second mesa, the top contact layer 7, the barrier layer 6, the absorber layer 5 and the drift layer 4 are first patterned to form the first mesa; then the bottom contact layer 3 and the DBR reflective layer 2 are patterned to form the second mesa.

Specifically, firstly, epitaxial layer materials are formed on the substrate layer 1 , followed by DBR reflective layer 2 , bottom contact layer 3 , drift layer 4 , absorption layer 5 , barrier layer 6 , and top contact layer 7 . Then, a reasonable pattern of the mask plate is designed, and the first mesa pattern on the mask plate is transferred to the epitaxial wafer by using a photolithography process. Using an etching process, the first mesa of the device is prepared and etched to the bottom contact layer 3 . Afterwards, the pattern of the second mesa on the mask plate is transferred to the epitaxial wafer by using a photolithography process, and the second mesa of the device is prepared by using an etching process, and etched to the substrate layer 1 .

Further, in specific implementation, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, as shown in FIG. 2 , it may further include: a passivation layer 8 located on the surface of the first mesa and the surface of the second mesa. Preferably, the material of the passivation layer 8 may be SiO ₂ to protect the device.

It should be noted that the passivation layer 8 is not a complete film structure, but has a pattern of diffusion windows, so as to free up the position of the electrode layer and part of the position of the first mesa to be fabricated later. In the process of making the passivation layer 8, a layer of passivation layer material is firstly deposited on the surfaces of the first mesa and the second mesa; then patterning is performed on the passivation layer material to form a pattern of the passivation layer with a diffusion window.

Specifically, first deposit and grow surface passivation layer material on the surface of the first mesa and the second mesa, then transfer the metal window pattern to the passivation layer by photolithography process, and etch the passivation layer to form the diffusion window by dry etching.

Further, in specific implementation, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, as shown in FIG. 2 , it may also include: a metal electrode layer 9 located on both sides of the upper surface of the first mesa and on both sides of the upper surface of the second mesa and in contact with the passivation layer 8.

Preferably, the metal electrode layer 9 may be a titanium/platinum/gold (Ti/Pt/Au) metal electrode layer. In the process of making the metal electrode layer 9, the pattern of the metal electrode layer on the mask plate is first transferred to the device with the passivation layer 8 through a photolithography process, and then a Ti/Pt/Au metal electrode layer is formed on the device with the passivation layer 8, and the redundant metal layer is removed by chemical stripping, so that the fabricated metal electrode layer is located on both sides of the upper surface of the first mesa and both sides of the upper surface of the second mesa and is in contact with the passivation layer 8. In this way, after the metal electrode layer 9 is manufactured, processes such as packaging can be further completed, and then put into application.

Further, in specific implementation, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, as shown in FIG. 2 , it may further include: a buffer layer 10 located between the substrate layer 1 and the DBR reflective layer 2 . The buffer layer 10 can be used to relieve the stress between the substrate layer 1 and the DBR reflective layer 2 .

It should be noted that, during the process of generating the epitaxial layer material on the substrate layer 1 , specifically, the buffer layer 10 may be generated before the DBR reflective layer 2 is generated. During the process of manufacturing the second mesa, the bottom contact layer 3 , the DBR reflective layer 2 and the buffer layer 10 can be etched simultaneously to form the second mesa.

Further, in specific implementation, in the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, the bottom contact layer 3 can be an n-type doped bottom contact layer; the drift layer 4 can be an unintentionally doped drift layer; the absorber layer 5 can be a multilayer absorber layer whose p-type doping concentration gradually decreases along the direction from the top contact layer to the bottom contact layer; the barrier layer 6 can be a p-type doped barrier layer; the top contact layer 7 can be a p-type doped top contact layer.

Preferably, the bottom contact layer 3 can be an n-type doped indium arsenide/aluminum arsenic antimonide (InAs/AlAsSb) bottom contact layer; the drift layer 4 can be an unintentionally doped InAsSb drift layer; the absorption layer 5 can be at least three layers of p-type doping concentration gradually decreasing InAs/InAsSb absorption layer along the direction from the top contact layer to the bottom contact layer; the barrier layer 6 can be a p-type doped AlAsSb barrier layer; the top contact layer 7 can be a p-type doped InAsSb top contact layer . In addition, the substrate layer 1 may be a gallium antimonide (GaSb) substrate layer; the buffer layer 2 may be a GaSb buffer layer; the DBR reflective layer 3 may be an AlAsSb/GaSb DBR reflective layer.

What needs to be added is that the type II superlattice photodetector provided by the present invention can be applied to traditional infrared photoelectric imaging, and can also be extended to the fields of free space optical communication and frequency comb spectrometer, and is expected to be applied to the field of optical computing after its performance is further improved.

Based on the same inventive concept, the embodiment of the present invention also provides a manufacturing method of a class II superlattice photodetector. Since the principle of solving the problem of the manufacturing method is similar to that of the aforementioned class II superlattice photodetector, the implementation of the manufacturing method can refer to the implementation of the class II superlattice photodetector, and the repetition will not be repeated.

During specific implementation, the manufacturing method of the class II superlattice photodetector provided by the embodiment of the present invention, as shown in Figure 3, specifically includes the following steps:

S301, forming a DBR reflective layer on the substrate layer.

Preferably, the substrate layer can be made of GaSb material; the DBR reflection layer can be made of AlAsSb/GaSb material.

S302, forming a UTC structure on the DBR reflective layer, which is a bottom contact layer, a drift layer, an absorption layer, a barrier layer and a top contact layer in sequence.

Preferably, the bottom contact layer can be made of InAs/AlAsSb material; the drift layer can be made of InAsSb material; the absorption layer can be set to at least three layers, and InAs/InAsSb material can be used; the barrier layer can be made of AlAsSb material; the top contact layer can be made of InAsSb material. Among them, the bottom contact layer is an n-type doped InAs/AlAsSb bottom contact layer; the drift layer is an unintentionally doped InAsSb drift layer; the absorption layer is at least three layers of InAs/InAsSb absorption layers whose p-type doping concentration gradually decreases along the direction from the top contact layer to the bottom contact layer; the barrier layer is a p-type doped AlAsSb barrier layer; the top contact layer is a p-type doped InAsSb top contact layer.

In the manufacturing method of the above-mentioned class II superlattice photodetector provided by the embodiment of the present invention, the above steps can be performed to manufacture a class II superlattice photodetector with a combination of a UTC structure and a DBR reflective layer. In the UTC structure, photogenerated carriers are excited in the unexhausted absorber layer, and only electrons are injected into the drift layer, which shortens the photocarrier transmission time of the device and improves the response speed of the device; The absorbing layer increases the light absorption of the device, and the design of the DBR reflective layer is flexible, suitable for different wavelength bands, which improves the design flexibility of the device. In the case of a sufficiently high light absorption, the thickness of the absorbing layer can be appropriately reduced, thereby reducing the dark current of the device and improving the photoelectric performance of the device.

Further, in specific implementation, in the method for manufacturing the above-mentioned Type II superlattice photodetector provided by the embodiment of the present invention, it may also include: first, patterning the top contact layer, barrier layer, absorption layer and drift layer to form the first mesa; then patterning the bottom contact layer and the DBR reflective layer to form the second mesa; the second mesa is larger than the first mesa. The present invention can design a reasonable mask pattern, transfer the first mesa pattern on the mask plate to the epitaxial wafer by using the photolithography process, prepare the first mesa surface of the device by using the etching process, etch to the bottom contact layer, similarly use the photolithography process to transfer the second mesa pattern on the mask plate to the epitaxial wafer, and use the etching process to prepare the second mesa surface of the device and etch to the substrate layer.

Further, in specific implementation, in the method for manufacturing the above-mentioned Type II superlattice photodetector provided by the embodiment of the present invention, it may also include: first depositing a passivation layer material on the surface of the first mesa and the second mesa; then performing a patterning process on the passivation layer material to form a pattern of the passivation layer with a diffusion window; finally forming a metal electrode layer on the first mesa and the second mesa formed with the diffusion window; the metal electrode layer is located on both sides of the upper surface of the first mesa and both sides of the upper surface of the second mesa and is in contact with the passivation layer. The invention can design a reasonable mask pattern, transfer the metal window pattern on the mask plate to the passivation layer through a photolithography process, etch the passivation layer to form a diffusion window through dry etching; then transfer the metal electrode layer pattern on the mask plate to the device with the passivation layer through the photolithography process, then generate a metal electrode layer on the device with the passivation layer, and remove the redundant metal layer by chemical stripping.

Further, in specific implementation, in the method for manufacturing the above-mentioned type II superlattice photodetector provided by the embodiment of the present invention, step S301 forms a DBR reflective layer on the substrate layer, which may specifically include: forming a buffer layer on the substrate layer, and forming a DBR reflective layer on the buffer layer. The buffer layer can relieve the stress between the substrate layer 1 and the DBR reflective layer 2 .

Taking the InAs/InAsSb photodetector as an example of the class II superlattice photodetector, the method for manufacturing the above class II superlattice photodetector provided by the embodiment of the present invention will be described in detail below, and the specific steps are as follows:

Step 1, generating an epitaxial layer material on the substrate layer;

Specifically, FIG. 4 is a schematic diagram of the structure of an epitaxial wafer of an InAs/InAsSb photodetector with a DBR reflective layer and a UTC structure obtained after step 1 is performed.

The epitaxial wafers are grown using Molecular beam epitaxy (MBE) equipment. As shown in Figure 4, the main structure of the epitaxial wafer includes substrate layer 1—GaSb substrate layer, buffer layer 10—GaSb buffer layer, reflective layer 2—AlAsSb/GaSb DBR reflective layer, bottom contact layer 3—n-type doped InAs/AlAsSb bottom contact layer, drift layer 4—unintentionally doped InAsSb drift layer, absorber layer 5—three layers of InAs/InAsSb absorber layer whose p-type doping concentration gradually decreases (along the direction of the top contact layer to the bottom contact layer), and barriers. Layer 6—p-type doped AlAsSb barrier layer, top contact layer 7—p-type doped InAsSb top contact layer. Among them, n-type doped InAs/AlAsSb bottom contact layer, unintentionally doped InAsSb drift layer, three p-type doped InAs/InAsSb absorber layers, p-type doped AlAsSb barrier layer, and p-type doped InAsSb top contact layer constitute the UTC structure.

Step 2, performing a patterning process on the top contact layer, barrier layer, absorber layer and drift layer to form a first mesa;

Specifically, FIG. 5 is a schematic cross-sectional view of the process of preparing a mesa-type top electrode InAs/InAsSb II superlattice photodetector with a DBR reflector and a UTC structure starting from the epitaxial wafer after performing step 2.

As shown in FIG. 5 , the first mesa is etched using a photolithographic masking process and an etching process, and stops at the surface of the bottom contact layer 3 . In specific implementation, a layer of photoresist is deposited on the epitaxial wafer, that is, a layer of photoresist is deposited on the top contact layer 7, and the corresponding mask is used to pass exposure, development and other processes, leaving only the photoresist on the surface of the first mesa to be formed, that is, using a photolithography process to transfer the first mesa pattern on the mask to the epitaxial wafer; then perform an etching process on the rest of the position except where the photoresist is located, until the surface of the bottom contact layer 3 stops, and finally peel off the photoresist, and then prepare the first mesa of the device.

Step 3, performing a patterning process on the bottom contact layer, the DBR reflective layer and the buffer layer to form a second mesa;

Specifically, FIG. 6 is a schematic cross-sectional view of the process of preparing a mesa-type bottom electrode InAs/InAsSb II superlattice photodetector with a DBR reflector and a UTC structure from the epitaxial wafer after performing step three.

As shown in FIG. 6 , the bottom contact layer 3 , the DBR reflective layer 2 and the buffer layer 10 are etched continuously using the photolithography mask process and the etching process to prepare the second mesa of the device. In specific implementation, continue to deposit a layer of photoresist on the epitaxial wafer, that is, deposit a layer of photoresist on the top contact layer 7 and the bottom contact layer 3, use the corresponding mask to pass through exposure, development and other processes, leaving only the photoresist on the surface of the second mesa and the first mesa to be formed, that is, use the photolithography process to transfer the second mesa pattern on the mask to the epitaxial wafer; then perform an etching process on the rest of the position except the position of the photoresist until the surface of the substrate layer 1 stops, and finally peel off the photoresist, and then prepare The second mesa of the device. Wherein, the second mesa is larger than the first mesa; the substrate layer 1 is larger than the second mesa.

Step 4, depositing a layer of passivation layer material on the surface of the first mesa and the second mesa;

Specifically, as shown in FIG. 7 , a SiO ₂ passivation film is grown on the first mesa and the second mesa formed in Step 4, so as to generate the pattern of the passivation layer 8 .

Step 5, performing a patterning process on the passivation layer material to form a pattern of the passivation layer with a diffusion window;

Specifically, as shown in FIG. 8 , the passivation layer 8 at the first mesa and the second mesa of the device are etched to open windows by using a photolithography mask process and an etching process. During specific implementation, continue to deposit a layer of photoresist on the structure formed in the above step 4, use the corresponding mask to remove the photoresist on the position of the diffusion window pattern to be formed through exposure, development and other processes, that is, transfer the metal window pattern to the passivation layer 8 through a photolithography process, etch the passivation layer 8 to form the pattern of the diffusion window through a dry etching process, and finally peel off the photoresist to prepare a passivation layer with a diffusion window.

Step 6, forming a metal electrode layer on the first mesa and the second mesa formed with the diffusion window;

Specifically, as shown in FIG. 9, on the first mesa and the second mesa of the device, a photolithography process is used to transfer the photolithographic mask pattern of the metal electrode to the mesa, and then a metal electrode layer 9 is grown at the opening of the pattern, such as Ti/Pt/Au ohmic contact metal. In the specific implementation, first, continue to deposit a layer of photoresist on the structure formed in the above step 5, and use the corresponding mask to pass exposure, development and other processes, leaving only the photoresist on the position in the diffusion window other than the metal electrode layer (that is, the middle position of the first mesa). Afterwards, on the basis of the remaining photoresist, Ti/Pt/Au ohmic contact metal is grown at the opening of the pattern, and finally the excess metal is removed by chemical stripping to produce the metal pad electrode layer 9 . The manufactured metal electrode layer 9 is specifically located on both sides of the upper surface of the first mesa and both sides of the upper surface of the second mesa and is in contact with the passivation layer 8 .

Finally, the devices of the prepared embodiments can be further subjected to packaging and other processes to test the photoelectric performance of the devices, and then put them into use.

For a more specific working process of the above steps, reference may be made to the corresponding content disclosed in the foregoing embodiments, which will not be repeated here.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same or similar parts of each embodiment can be referred to each other. As for the manufacturing method disclosed in the embodiment, since it corresponds to the type II superlattice photodetector disclosed in the embodiment, the description is relatively simple, and for the related parts, please refer to the description of the type II superlattice photodetector.

In summary, a type II superlattice photodetector provided by an embodiment of the present invention includes: a substrate layer, a DBR reflective layer and a UTC structure sequentially positioned on the substrate layer; the UTC structure includes a stacked bottom contact layer, a drift layer, an absorption layer, a barrier layer and a top contact layer. The above-mentioned type II superlattice photodetector is designed with a combination of UTC structure and DBR reflective layer. In the UTC structure, photo-generated carriers are excited in the unexhausted absorbing layer, and only electrons are injected into the drift layer, which shortens the photo-generated carrier transmission time of the device and improves the response speed of the device. , the design flexibility of the device is improved, and the thickness of the absorbing layer can be appropriately reduced under the condition of satisfying a sufficiently high light absorption, thereby reducing the dark current of the device and improving the photoelectric performance of the device. In addition, the present invention also provides a corresponding manufacturing method for the type II superlattice photodetector, which further makes the above-mentioned type II superlattice photodetector more practical, and the manufacturing method has corresponding advantages.

Finally, it should also be noted that in this document, relational terms such as first and second etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements but also other elements not expressly listed or which are inherent in such a process, method, article or apparatus. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The class II superlattice photodetector provided by the present invention and its manufacturing method have been introduced in detail above. The principles and implementation methods of the present invention have been explained by using specific examples. The descriptions of the above examples are only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and application range. In summary, the content of this specification should not be understood as limiting the present invention.

Claims (10)

1. A class II superlattice photodetector, comprising: a substrate layer, a DBR reflection layer and a UTC structure sequentially positioned on the substrate layer;

the UTC structure comprises a bottom contact layer, a drift layer, an absorption layer, a barrier layer and a top contact layer which are stacked.

2. The type II superlattice photodetector of claim 1, wherein the top contact layer, the barrier layer, the absorber layer, and the drift layer are patterned to form a first mesa of the type II superlattice photodetector;

the bottom contact layer and the pattern of the DBR reflection layer form a second mesa of the class II superlattice photodetector; the second mesa is larger than the first mesa.

3. The class II superlattice photodetector of claim 2, further comprising:

and a passivation layer positioned on the first mesa surface and the second mesa surface.

4. A class II superlattice photodetector as in claim 3, further comprising:

and the metal electrode layers are positioned on two sides of the upper surface of the first mesa and two sides of the upper surface of the second mesa and are in contact with the passivation layer.

5. The class II superlattice photodetector of claim 1, further comprising:

and a buffer layer between the substrate layer and the DBR reflection layer.

6. The type II superlattice photodetector of claim 1, wherein said bottom contact layer is an n-doped bottom contact layer;

the drift layer is an unintentionally doped drift layer;

the absorption layer is formed by sequentially reducing the p-type doping concentration of multiple layers in a gradient manner along the direction of the top contact layer to the bottom contact layer;

the barrier layer is a p-type doped barrier layer;

the top contact layer is a p-type doped top contact layer.

7. A method of fabricating a class II superlattice photodetector as defined in any one of claims 1 to 6, comprising:

forming a DBR reflection layer on the substrate layer;

and forming a UTC structure on the DBR reflecting layer, wherein the UTC structure comprises a bottom contact layer, a drift layer, an absorption layer, a barrier layer and a top contact layer in sequence.

8. The method of fabricating a class II superlattice photodetector as defined in claim 7, further comprising:

patterning the top contact layer, the barrier layer, the absorption layer and the drift layer to form a first mesa;

patterning the bottom contact layer and the DBR reflecting layer to form a second mesa; the second mesa is larger than the first mesa.

9. The method of fabricating a class II superlattice photodetector as defined in claim 8, further comprising:

depositing a passivation layer material on the surfaces of the first table top and the second table top;

patterning the passivation layer material to form a pattern of the passivation layer with a diffusion window;

forming a metal electrode layer on the first mesa and the second mesa on which the diffusion window is formed; the metal electrode layers are positioned on two sides of the upper surface of the first mesa and two sides of the upper surface of the second mesa and are in contact with the passivation layer.

10. The method of fabricating a class II superlattice photodetector as defined in claim 7, wherein forming the DBR reflective layer on the substrate layer comprises:

a buffer layer is formed on the substrate layer, and a DBR reflective layer is formed on the buffer layer.