Photoelectric detector and photoelectric communication system

Abstract

The invention discloses a photoelectric detector and a photoelectric communication system. The photoelectric detector comprises a substrate and a photoelectric conversion structure, the photoelectric conversion structure is arranged on one side of the substrate in a first direction, and the first direction is the thickness direction of the substrate; the photoelectric conversion structure comprises a plurality of photon absorption layers, the photon absorption layers are arranged in the second direction, the adjacent photon absorption layers make contact with each other, and the second direction is perpendicular to the first direction. When the above scheme is adopted, the plurality of photon absorption layers of the photoelectric conversion structure are arranged along the direction perpendicular to the thickness direction of the substrate, that is, the plurality of photon absorption layers are arranged along the width or length direction of the substrate, and the active absorption region of the photoelectric detector has a large photosensitive surface, so that the coupling efficiency of incident light can be improved; the responsivity of the photoelectric detector can be improved, the bandwidth of the photoelectric detector can be improved, and the requirements of an ultra-wideband communication system can be met.

Description

Technical Field

[0001] This application relates to the field of communications, and particularly to a photodetector and an optical communication system. Background Art

[0002] Radio frequency photonics technology combines wireless technology with optoelectronic technology to study the applications of optoelectronic devices and modules in the microwave frequency band in future radio frequency systems. The aim is to use light as the information carrier to improve the speed of data exchange and processing in order to meet the application challenges of emerging scenarios such as artificial intelligence, autonomous driving, and 5G. Currently, most optoelectronic systems are composed of discrete optoelectronic components with direct bandgaps such as optical / electrical and electrical / optical components. However, future wireless communication systems require smaller device and optoelectronic system sizes, lower power consumption, and higher integration.

[0003] A photodetector (PD) is the detection end of an optoelectronic system and also the interface between a photonic integrated circuit and a traditional integrated circuit. Its bandwidth performance determines the speed limit of the entire wireless communication system. Existing photodetectors are usually PIN-type photodetectors (PIN-PD), whose incident mode is free-space optical coupling and the photosensitive surface is small, resulting in a low responsivity of the photodetector. In addition, the P and N electrode metals will reflect or absorb the incident free-space light, further reducing the responsivity of the photodetector. Summary of the Invention

[0004] This application provides a photodetector and an optical communication system to improve the responsivity of the photodetector.

[0005] In a first aspect, this application provides a photodetector, which may include a substrate and a photoelectric conversion structure. In a first direction, the photoelectric conversion structure is disposed on one side of the substrate, and the first direction may be the thickness direction of the substrate. The photoelectric conversion structure may include a plurality of photon absorption layers, and the plurality of photon absorption layers are arranged in a second direction, and adjacent photon absorption layers are in contact with each other. The second direction may be perpendicular to the first direction.

[0006] In the technical solution provided by this application, the plurality of photon absorption layers of the photoelectric conversion structure are arranged in a direction perpendicular to the thickness direction of the substrate, that is, the plurality of photon absorption layers are arranged along the width or length direction of the substrate. The active absorption region of the photodetector has a large photosensitive surface, which can improve the incident light coupling efficiency, thereby improving the responsivity of the photodetector, and can also improve the bandwidth of the photodetector, meeting the requirements of an ultra-wideband communication system.

[0007] In a specific feasible implementation, the photodetector may further include an optical waveguide structure. In the first direction, the optical waveguide structure and the photoelectric conversion structure are disposed on the same side of the substrate; the optical waveguide structure extends along a third direction, and the third direction may be perpendicular to the first direction and is disposed at an angle to the second direction; in the third direction, the optical waveguide structure is located on one side of the photoelectric conversion structure, and there is a gap between the optical waveguide structure and the photoelectric conversion structure, and at least a part of the projection of the optical waveguide structure coincides with the projection of the plurality of photon absorption layers. It can ensure that the optical signal incident from the optical waveguide structure is confined in the active absorption region, realize a high overlap degree of the mode spot at the coupling end face of the optical waveguide structure and the photoelectric conversion structure, improve the optical coupling efficiency, enable efficient optical coupling between the optical waveguide structure and the active absorption region, ensure that the optical signal is fully absorbed, and enhance the photoelectric conversion efficiency of the photodetector.

[0008] In a specific feasible implementation, the cross-sectional shape of the optical waveguide structure along the second direction may be rectangular, square or circular. The shape of the optical waveguide structure is relatively diverse and can adapt to various forming processes.

[0009] In a specific feasible implementation, the cross-sectional area of the optical waveguide structure may gradually decrease from the end far from the photoelectric conversion structure to the end close to the photoelectric conversion structure. The optical waveguide structure may be a tapered structure, which can improve the optical coupling efficiency.

[0010] In a specific feasible implementation, a filling layer may be disposed between the optical waveguide structure and the photoelectric conversion structure. In the third direction, both sides of the filling layer are in contact with the optical waveguide structure and the plurality of photon absorption layers respectively. The filling layer can fill the gap between the optical waveguide structure and the photoelectric conversion structure, reduce the sensitivity of the optical coupling efficiency to the size of this gap, reduce the influence of the size of this gap on the optical coupling efficiency, avoid the requirement for sub-micron processing of the width of this gap, make the flexibility of the gap size between the optical waveguide structure and the photoelectric conversion structure relatively high, realize high process tolerance, and simplify the process requirements. Moreover, the filling layer can prevent the light incident on this gap from leaking to the substrate, improve the confinement ability of the active absorption region to the incident light, and improve the optical coupling efficiency.

[0011] In a specific feasible implementation, the filling layer may extend towards the end of the optical waveguide structure far from the photoelectric conversion structure to wrap at least a part of the optical waveguide structure. It can improve the position stability of the optical waveguide structure.

[0012] In a specific feasible embodiment, the photodetector may further include a first contact layer and a second contact layer. In the second direction, the first contact layer and the second contact layer are respectively disposed on two sides of the photoelectric conversion structure and are respectively in contact with the photoelectric conversion structure. The first contact layer and the second contact layer are respectively disposed on two sides of the photoelectric conversion structure and are respectively in contact with the photoelectric conversion structure, forming electrodes with good ohmic contact. The first contact layer can form a p-type ohmic contact with the metal electrode, enabling the photo-generated holes to be collected by the electrode, thereby generating current in the external circuit. The second contact layer can form an n-type ohmic contact with the metal electrode, enabling the photo-generated electrons to be collected by the electrode, thereby generating current in the external circuit.

[0013] In a specific feasible embodiment, the first contact layer may include a first part and a second part connected to each other. The first part and the second part are arranged along a third direction. The third direction is perpendicular to the first direction and is set at an angle to the second direction. The second part is connected to the photoelectric conversion structure through the first part; in the second direction, the projected area of the first part may be greater than or equal to the projected area of the photoelectric conversion structure; in the third direction, the projected area of the first part may be smaller than the projected area of the second part. Thinning the thickness of the first part, that is, thinning the thickness of the part of the first contact layer corresponding to the photoelectric conversion structure in the second direction, can improve the ability of the active absorption region to confine the incident light, thereby improving the responsivity of the photodetector. Moreover, the first contact layer retains a relatively large ohmic contact area, which can reduce the ohmic contact resistance and at the same time achieve good ohmic contact.

[0014] In a specific feasible embodiment, in the second direction, the projected area of the second contact layer may be smaller than or equal to the projected area of the photoelectric conversion structure. This facilitates the integrated formation of the second contact layer and the photoelectric conversion structure.

[0015] In a specific feasible embodiment, in the second direction, the projected area of the photoelectric conversion structure may be smaller than the projected area of the first contact layer, and the projected area of the second contact layer may be smaller than or equal to the projected area of the photoelectric conversion structure. The projected areas of the second contact layer and the photoelectric conversion structure are smaller than the projected area of the first contact layer, achieving a reduction in the junction area to reduce the junction capacitance, thereby further improving the bandwidth of the photodetector.

[0016] In a specific feasible embodiment, the photoelectric conversion structure may further include a blocking layer. In the second direction, the blocking layer is located on one side of the plurality of photon absorption layers and is in contact with the photon absorption layer closest to the blocking layer. The function of the blocking layer is to utilize the heterojunction potential barrier to block the diffusion of electrons in the direction of the p electrode.

[0017] In a specific feasible embodiment, the optoelectronic conversion structure may further include a smoothing layer. In the second direction, the smoothing layer is located on the other side of the plurality of photon absorption layers and is in contact with the photon absorption layer closest to the smoothing layer.

[0018] In a specific feasible embodiment, the optoelectronic conversion structure may further include a cliff layer. In the second direction, the cliff layer is located on the side of the smoothing layer away from the plurality of photon absorption layers, and the cliff layer is in contact with the smoothing layer. The function of the cliff layer is to form a PN junction with the photon absorption layer to generate a depletion electric field, enabling the photo-generated electron-hole pairs to be quickly separated. The function of the smoothing layer is to smooth the band discontinuity between the material of the photon absorption layer and the material of the cliff layer. The band discontinuity will cause barrier spikes, which affect the transport of carriers and thus the saturation output current and 3dB bandwidth of the photodetector. The setting of the smoothing layer allows carriers to quickly cross the barrier spikes and alleviates the accumulation of photo-generated carriers.

[0019] In a specific feasible embodiment, the optoelectronic conversion structure may further include a collection layer. In the second direction, the collection layer is located on the side of the cliff layer away from the smoothing layer, and the collection layer is in contact with the cliff layer. The function of the collection layer is to help the n electrode collect photo-generated electrons and avoid the accumulation of photo-generated electrons.

[0020] In a specific feasible embodiment, the optoelectronic conversion structure may further include a sub-contact layer. In the second direction, the sub-contact layer is located on the side of the collection layer away from the cliff layer, and the sub-contact layer is in contact with the collection layer. The function of the sub-contact layer is to form an n-type ohmic contact with the metal electrode so that photo-generated electrons can be collected by the electrode, thereby generating a current in the external circuit.

[0021] In a second aspect, the present application also provides an optoelectronic communication system. The optoelectronic communication system may include a circuit board, a first circuit, a second circuit, and a photodetector according to any one of the feasible embodiments in the first aspect above. The first circuit, the second circuit, and the photodetector are disposed on the circuit board, and the first circuit can be connected to the second circuit through the photodetector. The responsivity of the photodetector is relatively high, and the performance of the optoelectronic communication system is relatively excellent. Description of the Drawings

[0022] Figure 1 It is a three-dimensional structure schematic diagram of the photodetector provided by the present application;

[0023] Figure 2 It is a top view structure schematic diagram of the photodetector provided by the present application;

[0024] Figure 3 It is an application scenario schematic diagram of the photodetector provided by the present application;

[0025] Figure 4 Schematic three-dimensional structure diagram of the photodetector provided by the present application;

[0026] Figure 5 Top view of a partial structure of the photodetector provided by the present application;

[0027] Figure 6 Top view of a partial structure of the photodetector provided by the present application;

[0028] Figure 7 Schematic three-dimensional diagram of a partial structure of the photodetector provided by the present application;

[0029] Figure 8 Schematic three-dimensional diagram of a partial structure of the photodetector provided by the present application.

[0030] Reference numerals:

[0031] 100 - Substrate; 200 - Photoelectric conversion structure; 300 - Optical waveguide structure; 400 - Filling layer;

[0032] 201 - Photon absorption layer; 202 - First contact layer; 203 - Second contact layer; 204 - Barrier layer;

[0033] 205 - Smoothing layer; 206 - Cliff layer; 207 - Collection layer; 208 - Auxiliary contact layer;

[0034] 2021 - First part; 2022 - Second part. Detailed implementation manners

[0035] In order to make the objectives, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below in conjunction with the accompanying drawings. However, the exemplary embodiments can be implemented in various forms and should not be construed as being limited to the embodiments described herein. The same reference numerals in the drawings represent the same or similar structures, and thus the repeated descriptions thereof will be omitted. The words expressing positions and directions described in the embodiments of the present application are all illustrated with reference to the drawings, but can be changed according to needs, and all the changes made are included in the protection scope of the present application. The drawings in the embodiments of the present application are only used to illustrate the relative position relationship and do not represent the true proportion.

[0036] In the following description, specific details are set forth to facilitate the understanding of the present application. However, the embodiments of the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the embodiments of the present application. Therefore, the present application is not limited by the specific implementation manners disclosed below.

[0037] For ease of understanding, first, the application scenarios of the photodetector involved in this application are described. The photodetector provided in the embodiments of this application can be adapted to an optical communication system, such as a high-speed on-chip integrated optical communication system. As a possibility, the optical communication system can include a circuit board, a first circuit, a second circuit, and a photodetector. The first circuit, the second circuit, and the photodetector can be disposed on the circuit board, and the first circuit is connected to the second circuit through the photodetector. Among them, the first circuit can be a photonic integrated circuit, and the second circuit can be a traditional integrated circuit.

[0038] In the related art, a PIN-type photodetector (PIN-PD) is usually adopted for the photodetector. The light incident mode is free-space optical coupling, and the photosensitive surface is small, resulting in a low responsivity of the photodetector. In addition, the p and n electrode metals will reflect or absorb the incident free-space light, further reducing the responsivity of the photodetector. Based on this, the embodiments of this application provide a photodetector to improve the responsivity of the photodetector.

[0039] First, refer to Figure 1 and Figure 2 , Figure 1 which shows a schematic three-dimensional structure diagram of the photodetector provided in this application, Figure 2 and Figure 1 shows a schematic top view structure diagram of the photodetector provided in this application. In the coordinate directions of the following figures, the direction indicated by the z-axis represents the first direction, the direction indicated by the x-axis represents the second direction, and the direction indicated by the y-axis represents the third direction. As Figure 2 and

[0040] shown, the photodetector provided in the embodiments of this application can include a substrate 100 and a photoelectric conversion structure 200. The substrate 100 can be a wafer such as silicon (Si), silicon nitride (SiNx), silicon dioxide (SiO2), silicon carbide (SiC), and diamond (C). Specifically, the first direction can be the thickness direction of the substrate 100, the second direction can be perpendicular to the first direction, and the third direction can be perpendicular to the first direction and arranged at an angle with the second direction. For example, the third direction can be perpendicular to the first direction and the second direction. More specifically, the second direction can be the width direction of the substrate 100, and the third direction can be the length direction of the substrate 100, or the second direction can be the length direction of the substrate 100, and the third direction can be the width direction of the substrate 100. In the first direction, the photoelectric conversion structure 200 is disposed on one side of the substrate 100. The photoelectric conversion structure 200 can include a plurality of photon absorption layers 201. The plurality of photon absorption layers 201 are arranged along the second direction, and adjacent photon absorption layers 201 are in contact. The function of the photon absorption layer 201 is to absorb incident photons, generate electron-hole pairs, and realize photoelectric conversion. The plurality of photon absorption layers 201 constitute an active absorption region.

[0040] The photodetector provided by the embodiment of the present application has multiple photon absorption layers 201 of the optoelectronic conversion structure 200 arranged along the width or length direction of the substrate 100. The active absorption region of the photodetector has a large photosensitive surface, which can improve the incident light coupling efficiency, enhance the responsivity of the photodetector, and increase the bandwidth of the photodetector, meeting the requirements of the ultra-wideband communication system.

[0041] In a specific implementation, the material of the photon absorption layer 201 can be indium gallium arsenide (InGaAs). The optoelectronic conversion structure 200 can include four photon absorption layers 201. Specifically, the optoelectronic conversion structure 200 can include three first photon absorption layers and one second photon absorption layer arranged in sequence along the second direction, where the second photon absorption layer can also be referred to as a depletion photon absorption layer, and the functions of the first photon absorption layer and the second photon absorption layer are both to achieve optoelectronic conversion.

[0042] During specific formation, the optoelectronic conversion structure 200 can be formed by using the lateral aspect ratio trapping (LART) technique, and the type of the photodetector can be a uni-traveling carrier photodiode (UTC-PD). The uni-traveling carrier photodetector only relies on electrons as active carriers, has the characteristics of fast response and high saturation output, and can exhibit excellent performance under high light intensity radiation and large injection conditions. Compared with the traditional PIN photodiode (PIN-PD), since the electron mobility is much greater than the hole mobility, the drift velocity of electrons has an obvious advantage, which can effectively suppress the space charge effect. Therefore, the uni-traveling carrier photodetector can avoid the bandwidth limitation of holes and maintain a high-speed signal output under large incident light intensity and large current conditions. Moreover, the bandwidth performance of the uni-traveling carrier photodetector is much greater than the upper limit of the PIN photodetector, and under the same bandwidth, the RF power output ability of the uni-traveling carrier photodetector is also higher than that of the PIN photodetector.

[0043] Figure 3 The schematic diagram of the application scenario of the photodetector provided by the present application is shown. As Figure 3 shown, the photodetector can be formed on an optoelectronic integrated wafer, and can further form a chip product, such as a microelectronic control chip, a silicon-based optoelectronic functional chip, etc., and can then be applied to scenarios such as high-speed data center communication, broadband microwave photon processing, super-resolution radar imaging, and intelligent photon processing.

[0044] Continue to refer to Figure 1 and Figure 2As shown, the photodetector further includes an optical waveguide structure 300. In the first direction, the optical waveguide structure 300 and the photoelectric conversion structure 200 are disposed on the same side of the substrate 100. The optical waveguide structure 300 can extend along the third direction. In the third direction, the optical waveguide structure 300 can be located on one side of the photoelectric conversion structure 200, and there is a gap between the optical waveguide structure 300 and the photoelectric conversion structure 200. In the third direction, at least a part of the projection of the optical waveguide structure 300 coincides with the projection of the plurality of photon absorption layers 201, that is, at least a part of the projection of the optical waveguide structure 300 is within the projection range of the plurality of photon absorption layers 201. This can ensure that the optical signal incident from the optical waveguide structure 300 is confined in the active absorption region, realize a high overlap degree of the mode spot at the coupling end face of the optical waveguide structure 300 and the photoelectric conversion structure 200, improve the optical coupling efficiency, enable efficient optical coupling between the optical waveguide structure 300 and the active absorption region, ensure that the optical signal is fully absorbed, and enhance the photoelectric conversion efficiency of the photodetector.

[0045] In specific implementation, the height of the optical waveguide structure 300 can be less than or equal to the height of the photoelectric conversion structure 200. The height mentioned here refers to the dimension in the first direction. In specific forming, the material of the optical waveguide structure 300 can be silicon (Si). The structure of the photodetector along the third direction can be defined by micro-nano processing. For example, the photoelectric conversion structure 200 and the optical waveguide structure 300 are formed by using the lateral aspect ratio capture technology, realizing the integration of the photoelectric conversion structure 200 and the optical waveguide structure 300 on a silicon substrate. The forming of the photodetector is relatively convenient and is conducive to subsequent electrode processes, ensuring good ohmic contact.

[0046] In specific implementation, the cross-sectional shape of the optical waveguide structure 300 along the second direction can be rectangular, square, circular, etc. That is, the optical waveguide structure 300 can be rectangular columnar, square columnar, cylindrical, etc. The shape of the optical waveguide structure 300 is relatively diverse and can adapt to various forming processes. In specific implementation, from the end far away from the photoelectric conversion structure 200 to the end close to the photoelectric conversion structure 200, the cross-sectional area of the optical waveguide structure 300 gradually decreases, that is, the optical waveguide structure 300 can be a conical structure, which can improve the optical coupling efficiency. Figure 1 and Figure 2 The case where the optical waveguide structure 300 is a conical structure is illustrated.

[0047] As a possible implementation, a filling layer 400 may be provided between the optical waveguide structure 300 and the optoelectronic conversion structure 200. In the third direction, both sides of the filling layer 400 are respectively in contact with the optical waveguide structure 300 and the plurality of photon absorption layers 201. Specifically, the material of the filling layer 400 may be silicon nitride (SiNx), and the refractive index of the filling layer 400 is between the refractive index of the optical waveguide structure 300 and the refractive index of the photon absorption layer 201. The filling layer 400 can fill the gap between the optical waveguide structure 300 and the optoelectronic conversion structure 200, can reduce the sensitivity of the optical coupling efficiency to the size of this gap, reduce the influence of the size of this gap on the optical coupling efficiency, can avoid the requirement for sub-micron processing of the width of this gap, make the flexibility of the gap size between the optical waveguide structure 300 and the optoelectronic conversion structure 200 relatively high, can achieve high process tolerance, and simplify the process requirements. Moreover, the filling layer 400 can prevent the light incident on this gap from leaking to the substrate 100, can improve the confinement ability of the active absorption region to the incident light, can improve the optical coupling efficiency, and finally realize a high-speed photodetector with high coupling efficiency.

[0048] In specific implementation, the filling layer 400 may extend towards the end of the optical waveguide structure 300 away from the optoelectronic conversion structure 200. The filling layer 400 may wrap the entire optical waveguide structure 300, or the filling layer 400 may wrap a part of the optical waveguide structure 300, which can improve the position stability of the optical waveguide structure 300. When the optical waveguide structure 300 is a columnar structure, the filling layer 400 may also be a columnar structure; when the optical waveguide structure 300 is a conical structure, the filling layer 400 may be a conical structure or a columnar structure. Figure 1 and Figure 2 illustrates the case where the filling layer 400 wraps the entire optical waveguide structure 300 and the filling layer 400 is a columnar structure.

[0049] Figure 4 shows a schematic three-dimensional structure diagram of the photodetector provided by the present application. As Figure 4 shown, when a filling layer 400 is provided between the optical waveguide structure 300 and the optoelectronic conversion structure 200, the photodetector has three waveguides, namely the optical waveguide structure 300, the filling layer 400, and the optoelectronic conversion structure 200, and two optical couplings occur between the three waveguides. Figure 4 schematically shows two optical coupling end faces. One of them may be called the first optical coupling end face a, where the optical waveguide structure 300 and the filling layer 400 perform optical coupling at the first optical coupling end face a, and the other may be called the second optical coupling end face b, where the filling layer 400 and the optoelectronic conversion structure 200 perform optical coupling at the second optical coupling end face b.

[0050] Figure 5 shows a top view of a partial structure of the photodetector provided by the present application. As Figure 5As shown, the photodetector further includes a first contact layer 202 and a second contact layer 203. The material of the first contact layer 202 can be indium gallium arsenide (InGaAs), and the material of the second contact layer 203 can be indium phosphide (InP). In the second direction, the first contact layer 202 and the second contact layer 203 can be respectively disposed on both sides of the photoelectric conversion structure 200 and respectively contact the photoelectric conversion structure 200. Among them, the first contact layer 202 can be a p-type contact layer, and the second contact layer 203 can be an n-type contact layer. The function of the first contact layer 202 is to form a p-type ohmic contact with the metal electrode, so that the photo-generated holes can be collected by the electrode, thereby generating a current in the external circuit; the function of the second contact layer 203 is to form an n-type ohmic contact with the metal electrode, so that the photo-generated electrons can be collected by the electrode, thereby generating a current in the external circuit.

[0051] In a specific implementation, the first contact layer 202 can include a first part 2021 and a second part 2022 connected to each other. The first part 2021 and the second part 2022 are arranged along the third direction. The second part 2022 is connected to the photoelectric conversion structure 200 through the first part 2021, and the first part 2021 and the second part 2022 can be integrally formed. In the second direction, the projected area of the first part 2021 is greater than or equal to the projected area of the photoelectric conversion structure 200. In Figure 5 this case, in the second direction, the projected area of the first part 2021 is equal to the projected area of the photon absorption layer 201, thereby indicating that the projected area of the first part 2021 is equal to the projected area of the photoelectric conversion structure 200. In the third direction, the projected area of the first part 2021 is smaller than the projected area of the second part 2022, which can be understood as the thickness of the first part 2021 is smaller than the thickness of the second part 2022. The thickness mentioned here refers to the dimension in the second direction. Thinning the thickness of the first part 2021, that is, thinning the thickness of the part of the first contact layer 202 corresponding to the photoelectric conversion structure 200 in the second direction, can reduce the escape of incident light to the first contact layer 202, improve the confinement ability of the active absorption region to incident light, increase the incident light absorption rate, thereby improving the responsivity of the photodetector. Moreover, the first contact layer 202 retains a large ohmic contact area, can reduce the ohmic contact resistance, and can achieve good ohmic contact at the same time.

[0052] In specific implementation, in the second direction, the projected area of the second contact layer 203 can be less than or equal to the projected area of the optoelectronic conversion structure 200, which is conducive to the formation of the second contact layer 203. For example, the projected area of the second contact layer 203 can be equal to the projected area of the optoelectronic conversion structure 200. Specifically, in the second direction, the second contact layer 203 is flush with the optoelectronic conversion structure 200, that is, the length of the second contact layer 203 is the same as that of the optoelectronic conversion structure 200, and the height of the second contact layer 203 is also the same as that of the optoelectronic conversion structure 200. The length mentioned here refers to the dimension in the third direction. In Figure 5 it is shown that in the second direction, by making the projected area of the second contact layer 203 equal to the projected area of the photon absorption layer 201, it is indicated that the projected area of the second contact layer 203 is equal to the projected area of the optoelectronic conversion structure 200.

[0053] Figure 6 FIG. shows a top view of a partial structure of the photodetector provided by the present application. Figure 7 FIG. shows a perspective view of a partial structure of the photodetector provided by the present application. As Figure 6 and Figure 7 shown, in the second direction, the projected area of the optoelectronic conversion structure 200 can be less than the projected area of the first contact layer 202, and the projected area of the second contact layer 203 can be less than or equal to the projected area of the optoelectronic conversion structure 200. In Figure 6 it is shown that in the second direction, by making the projected area of the photon absorption layer 201 less than the projected area of the first contact layer 202, it is indicated that the projected area of the optoelectronic conversion structure 200 is less than the projected area of the first contact layer 202, and by making the projected area of the second contact layer 203 equal to the projected area of the photon absorption layer 201, it is indicated that the projected area of the second contact layer 203 is equal to the projected area of the optoelectronic conversion structure 200.

[0054] In specific formation, a lateral aspect ratio capture technique can be used to form the optoelectronic conversion structure 200, the first contact layer 202, and the second contact layer 203 together. The lengths of the first contact layer 202, the optoelectronic conversion structure 200, and the second contact layer 203 can be the same, and then part of the optoelectronic conversion structure 200 and the second contact layer 203 can be etched away to make the projected areas of the second contact layer 203 and the optoelectronic conversion structure 200 less than the projected area of the first contact layer 202, so as to reduce the junction area and the junction capacitance, thereby further improving the bandwidth of the photodetector.

[0055] Figure 8 FIG. shows a perspective view of a partial structure of the photodetector provided by the present application. Different from Figure 7 Figure 8 it shows the situation when the first contact layer 202 and the second contact layer 203 are not partially removed. As Figure 8As shown, the optoelectronic conversion structure 200 may further include a blocking layer 204. In the second direction, the blocking layer 204 may be located on one side of the plurality of photon absorption layers 201. Specifically, the blocking layer 204 may be located between the first contact layer 202 and the plurality of photon absorption layers 201. In the second direction, one of the plurality of photon absorption layers 201 is located on one side, and one side of the blocking layer 204 is in contact with this one photon absorption layer 201, that is, one side of the blocking layer 204 is in contact with the one photon absorption layer 201 closest to it in the second direction, and the other side of the blocking layer 204 is in contact with the first contact layer 202. The material of the blocking layer 204 may be indium phosphide (InP). The function of the blocking layer 204 is to utilize the heterojunction barrier to block the diffusion of electrons in the direction of the p electrode. In specific implementation, the optoelectronic conversion structure 200 may further include a smoothing layer 205, a cliff layer 206, a collection layer 207, and a sub-contact layer 208, and each layer will be introduced separately below.

[0056] In the second direction, the smoothing layer 205 may be located on the other side of the plurality of photon absorption layers 201. Specifically, the smoothing layer 205 may be located between the second contact layer 203 and the plurality of photon absorption layers 201. In the second direction, another one of the plurality of photon absorption layers 201 is located on the other side, and the smoothing layer 205 is in contact with this another photon absorption layer 201, that is, the smoothing layer 205 is in contact with the one photon absorption layer 201 closest to it in the second direction. The material of the smoothing layer 205 may be indium gallium arsenide phosphide (InGaAsP). Specifically, the smoothing layer 205 may include a first smoothing layer and a second smoothing layer. The smoothing layer 205 may also be referred to as a bandgap smoothing layer.

[0057] In the second direction, the cliff layer 206 may be located on the side of the smoothing layer 205 away from the plurality of photon absorption layers 201, and the cliff layer 206 is in contact with the smoothing layer 205. The material of the cliff layer 206 may be indium phosphide (InP). The function of the cliff layer 206 is to form a PN junction with the photon absorption layer 201 to generate a depletion electric field, enabling the photo-generated electron-hole pairs to be quickly separated. Usually, the cliff layer 206 is heavily n-doped to extend the depletion electric field toward the photon absorption layer 201 side. The function of the smoothing layer 205 is to smooth the band discontinuity between the InGaAs material of the photon absorption layer 201 and the InP material of the cliff layer 206. The band discontinuity will cause potential barrier spikes, which affect the transport of carriers, and further affect the saturation output current and 3dB bandwidth of the photodetector. The setting of the smoothing layer 205 can enable the carriers to quickly cross the potential barrier spikes and relieve the accumulation of photo-generated carriers.

[0058] In the second direction, the collection layer 207 can be located on the side of the cliff layer 206 away from the smoothing layer 205, and the collection layer 207 is in contact with the cliff layer 206. The material of the collection layer 207 can be indium phosphide (InP). The function of the collection layer 207 is to help the n electrode collect photo-generated electrons and avoid the accumulation of photo-generated electrons.

[0059] In the second direction, the secondary contact layer 208 can be located on the side of the collection layer 207 away from the cliff layer 206, and the secondary contact layer 208 is in contact with the collection layer 207. The material of the secondary contact layer 208 can be indium phosphide (InP). Similar to the second contact layer 203, the secondary contact layer 208 can be an n-type contact layer. The function of the secondary contact layer 208 is to form an n-type ohmic contact with the metal electrode so that photo-generated electrons can be collected by the electrode, thereby generating a current in the external circuit.

[0060] In a specific implementation, the optoelectronic conversion structure 200 can sequentially include a blocking layer 204, a plurality of photon absorption layers 201, a smoothing layer 205, a cliff layer 206, a collection layer 207, and a secondary contact layer 208 in the second direction. A first contact layer 202 and a second contact layer 203 are respectively arranged on both sides of the optoelectronic conversion structure 200 in the second direction. Among them, the first contact layer 202 is in contact with the blocking layer 204, and the second contact layer 203 is in contact with the secondary contact layer 208.

[0061] Taking the optoelectronic conversion structure 200 including four photon absorption layers 201 as an example, the thicknesses of the three first photon absorption layers 201 can be 50 nm, 50 nm, and 70 nm respectively, and the doping concentrations can be 1x10 19 cm -3 、1x10 18 cm -3 and 5x10 17 cm -3 respectively. The thickness of the second photon absorption layer 201 can be 10 nm, and the doping concentration can be 1x10 16 cm -3 respectively. Thus, the total thickness of the four photon absorption layers 201 can be 180 nm. The thickness of the blocking layer 204 can be 20 nm, and the doping concentration can be 1x10 19 cm -3 . The thicknesses of the first smoothing layer and the second smoothing layer can be 2 nm and 2 nm respectively, and the doping concentrations can be 1x10 16 cm -3 and 1x10 16 cm -3 respectively; Figure 8Q1.4 in it indicates that the bandgap width of the first smoothing layer is 1.4 μm, and Q1.1 indicates that the bandgap width of the second smoothing layer is 1.1 μm. The components of the four elements In, Ga, As, and P in the smoothing layer can be determined by the bandgap width. The thickness of the cliff layer 206 can be 15 nm, and the doping concentration can be 1x10 16 cm -3 。The thickness of the collection layer 207 can be 220 nm, and the doping concentration can be 1x10 16 cm -3 。The thickness of the sub-contact layer 208 can be 50 nm, and the doping concentration can be 5x10 18 cm -3 。The thickness of the first contact layer 202 can be 3000 nm, and the doping concentration can be 4x10 19 cm -3 。The thickness of the second contact layer 203 can be 3000 nm, and the doping concentration can be 1x10 19 cm -3 。For the overall structure formed by the photoelectric conversion structure 200, the first contact layer 202, and the second contact layer 203, the dimension (height) along the first direction can be 0.34 μm; the dimension (thickness) along the second direction can be 6.5 μm, ensuring sufficient area for good contact with the electrodes.

[0062] It is measured that when light of 1550 nm passes through 5 μm of InGaAs, the absorption rate can reach 97%. Therefore, in order to confine the center of the incident light spot to the thinner active absorption region (180 nm), as shown in Figure 5 ,the first 5 μm of the first contact layer 202 along the third direction is thinned to form the first part 2021 to prevent light from escaping to the first contact layer 202. For the incident light with 3% light intensity in the subsequent 5 μm, the light path is no longer important. Therefore, the first contact layer 202 retains a thickness of 3000 nm in the subsequent 5 μm, which can ensure good ohmic contact for the subsequent electrode process. That is to say, the dimension (length) of the first contact layer 202 along the third direction can be 10 μm, where the length of the first part 2021 of the first contact layer 202 can be 5 μm, the thickness of the first part 2021 of the first contact layer 202 can be 300 nm, the length of the second part 2022 of the first contact layer 202 can be 5 μm, and the thickness of the second part 2022 of the first contact layer 202 can be 3000 nm. As shown in Figure 6 ,the lengths of the second contact layer 203 and the photoelectric conversion structure 200 can both be 5 μm, realizing the reduction of the junction area to reduce the junction capacitance.

[0063] The position of the optical waveguide structure 300 corresponds to the optoelectronic conversion structure 200 in the third direction. The thickness of the optical waveguide structure 300 can be 500 nm, and the height of the optical waveguide structure 300 can be the same as the height of the optoelectronic conversion structure 200. For example, the height of the optical waveguide structure 300 can be 0.34 μm, enabling efficient optical coupling between the optical waveguide structure 300 and the active absorption region. When the optical waveguide structure 300 is a tapered structure, the thickness of the end of the optical waveguide structure 300 away from the optoelectronic conversion structure 200 can be 500 nm, and the thickness of the other end can be 190 nm. At this time, the height of the optical waveguide structure 300 can be the height of the end of the optical waveguide structure 300 away from the optoelectronic conversion structure 200, that is, the height of the end of the optical waveguide structure 300 away from the optoelectronic conversion structure 200 can be the same as the height of the optoelectronic conversion structure 200. When the filling layer 400 wraps the entire optical waveguide structure 300, the height of the filling layer 400 can be 0.38 μm, and the thickness of the filling layer 400 can be 800 nm.

[0064] In this application, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone, where A and B can be singular or plural. In the text description of this application, the character " / " generally represents an "or" relationship between the front and back associated objects; in the formula of this application, the character " / " represents a "division" relationship between the front and back associated objects. "Including at least one of A, B, and C" can represent: including A; including B; including C; including A and B; including A and C; including B and C; including A, B, and C.

[0065] It can be understood that the various numerical numbers involved in the embodiments of this application are only for the convenience of description and are not used to limit the scope of the embodiments of this application. The magnitude of the sequence numbers of the above processes does not mean the order of execution, and the execution order of each process should be determined by its function and internal logic.

[0066] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application.

Claims

1. A photodetector, characterized in that, It includes a substrate and a photoelectric conversion structure. In a first direction, the photoelectric conversion structure is disposed on one side of the substrate, and the first direction is the thickness direction of the substrate; The photoelectric conversion structure includes a plurality of photon absorption layers, the plurality of photon absorption layers are arranged along a second direction, and adjacent photon absorption layers are in contact with each other, and the second direction is perpendicular to the first direction.

2. The photodetector according to claim 1, wherein It further includes an optical waveguide structure. In the first direction, the optical waveguide structure and the photoelectric conversion structure are disposed on the same side of the substrate; The optical waveguide structure extends along a third direction, and the third direction is perpendicular to the first direction and is disposed at an angle with the second direction; In the third direction, the optical waveguide structure is located on one side of the photoelectric conversion structure, and there is a gap between the optical waveguide structure and the photoelectric conversion structure, and at least a part of the projection of the optical waveguide structure coincides with the projection of the plurality of photon absorption layers.

3. The photodetector according to claim 2, characterized in that The cross-sectional shape of the optical waveguide structure along the second direction is rectangular, square or circular.

4. The photodetector according to claim 2 or 3, characterized in that, The cross-sectional area of the optical waveguide structure gradually decreases from the end far away from the photoelectric conversion structure to the end close to the photoelectric conversion structure.

5. The photodetector according to any one of claims 2 to 4, characterized in that A filling layer is disposed between the optical waveguide structure and the photoelectric conversion structure. In the third direction, both sides of the filling layer are in contact with the optical waveguide structure and the plurality of photon absorption layers respectively.

6. The photodetector according to claim 5, wherein, The filling layer extends towards the end of the optical waveguide structure far away from the photoelectric conversion structure to wrap at least a part of the optical waveguide structure.

7. The photodetector according to any one of claims 1 to 6, characterized in that It further includes a first contact layer and a second contact layer. In the second direction, the first contact layer and the second contact layer are respectively disposed on both sides of the photoelectric conversion structure and are in contact with the photoelectric conversion structure respectively.

8. The photodetector according to claim 7, wherein, The first contact layer includes a first part and a second part connected to each other. The first part and the second part are arranged along a third direction, the third direction is perpendicular to the first direction and is disposed at an angle with the second direction, and the second part is connected to the photoelectric conversion structure through the first part; In the second direction, the projected area of the first part is greater than or equal to the projected area of the photoelectric conversion structure; In the third direction, the projected area of the first part is smaller than the projected area of the second part.

9. The photodetector according to claim 8, wherein, In the second direction, the projected area of the second contact layer is smaller than or equal to the projected area of the photoelectric conversion structure.

10. The photodetector according to claim 7, characterized in that, In the second direction, the projected area of the photoelectric conversion structure is smaller than the projected area of the first contact layer, and the projected area of the second contact layer is smaller than or equal to the projected area of the photoelectric conversion structure.

11. The photodetector according to any one of claims 1 to 10, characterized in that, The photoelectric conversion structure further includes a blocking layer. In the second direction, the blocking layer is located on one side of the plurality of photon absorption layers and is in contact with the photon absorption layer closest to the blocking layer.

12. The photodetector according to claim 11, wherein The photoelectric conversion structure further includes a smoothing layer. In the second direction, the smoothing layer is located on the other side of the plurality of photon absorption layers and is in contact with the photon absorption layer closest to the smoothing layer.

13. The photodetector according to claim 12, wherein The optoelectronic conversion structure further includes a cliff layer, and in the second direction, the cliff layer is located on a side of the smooth layer away from the plurality of photon absorption layers, and the cliff layer is in contact with the smooth layer.

14. The photodetector according to claim 13, characterized in that, The optoelectronic conversion structure further includes a collection layer, and in the second direction, the collection layer is located on a side of the cliff layer away from the smooth layer, and the collection layer is in contact with the cliff layer.

15. The photodetector according to claim 14, characterized in that, The optoelectronic conversion structure further includes a sub-contact layer, and in the second direction, the sub-contact layer is located on a side of the collection layer away from the cliff layer, and the sub-contact layer is in contact with the collection layer.

16. An optoelectronic communication system, characterized in that, It includes a circuit board, a first circuit, a second circuit, and the photodetector according to any one of claims 1 to 15. The first circuit, the second circuit, and the photodetector are disposed on the circuit board, and the first circuit is connected to the second circuit through the photodetector.

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