Acceptance rate adjustable avalanche photodetector structure and avalanche photodetector thereof

Abstract

This invention discloses an avalanche photodetector structure with adjustable receiving rate and the avalanche photodetector thereof, including an APD. The APD is composed of a positive electrode layer, an absorption layer, a gain layer, a substrate layer, and a negative electrode layer. The gain layer includes a charge control region and an avalanche multiplication region, and the negative electrode layer includes only one negative electrode. It also includes multiple multiplication control regions, at least one additional avalanche multiplication region, and a corresponding additional negative electrode. The multiplication control regions and the additional avalanche multiplication region are all located within the gain layer. The avalanche multiplication regions and the negative electrodes are independently configured, and the multiplication control regions, avalanche multiplication regions, and negative electrodes are configured in a one-to-one correspondence. The multiplication control regions and the charge control regions can act individually or jointly to achieve modulation of two or more avalanche multiplication regions. Advantages: The gain of the APD of this invention can be adjusted over a wide range, achieving two levels of adjustment: low bandwidth high gain and high bandwidth low gain, which can be used to receive optical signals at different rates.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-speed optical communication and optical chip technology, especially the field of photodetector technology and optical access network, AI optical network, and specifically relates to an avalanche photodetector structure with adjustable receiving rate and an avalanche photodetector. BACKGROUND

[0002] The current optical access network is in the transition stage from 10G PON (Passive Optical Network) to the next generation high-speed PON technology. At present, it has been agreed in the industry that 50G PON will be selected as the next generation PON technology. ITU-T officially started the standardization work of 50G PON in 2018. So far, 50G PON has completed pilot operation, and deployment around 2025 has become the industry consensus.

[0003] The current standard defines two specifications of asymmetric and symmetric 50G PON. The upstream rate of asymmetric 50G PON is 25Gbps, and the downstream rate is 50Gbps. The upstream rate of symmetric 50G-PON is 50Gbps, and the downstream rate is 50Gbps. The difference between the two is the upstream rate. In order to support the smooth evolution of 50G PON, Combo-PON technology is the best choice. During the commercialization of 10G PON, Combo PON optical modules that combine GPON and 10G PON are welcomed by operators due to their good compatibility and convenience in actual engineering deployment. In the era of 50G PON, optical devices that coexist with GPON, 10G PON, and 50G PON are the core components to realize gigabit optical access.

[0004] Since PON optical modules are cost-sensitive, the industry currently uses avalanche photodetectors (APD) on the receiving side of the module. The SOA+PIN scheme has been abandoned due to high cost. However, the Combo-PON module receiving end of the standard protocol has the demand of 1 / 10 / 25 / 50Gbps four rates, and if 1 / 10 / 25 / 50G APD with different rates is used for the four rates respectively, it will bring certain challenges to module production and material management. Therefore, the industry currently generally expects that the same APD chip can completely cover the use demand of four rates.

[0005] Limited by the gain bandwidth product of the APD chip, the APD chip cannot improve the responsivity and optical bandwidth at the same time, and the optical bandwidth cannot be adjusted in a large range. The current commercial APD chip can be used by frequency superposition with the aid of electrical chips and other packaging means, but it can only support 1 / 10G rate at the same time, and it is difficult to improve to 25 / 50G rate. Because 25 / 50G rate requires higher optical bandwidth than 1 / 10G, the current APD chip can only consider bandwidth and responsivity by changing the design and process. SUMMARY

[0006] The purpose of the present application is to solve the problem and demand of the same APD for multiple rates, and the present application discloses an avalanche photodetector (APD) with adjustable receiving rate applied to a Comb PON optical module.

[0007] The traditional APD design only includes one avalanche gain region, and the technical solution of the present application includes two or more avalanche multiplication regions, and the avalanche multiplication regions can be controlled by the negative electrode, so that the APD of the present application can simultaneously control the gain and bandwidth, and can be compatible with 25G / 50Gbps rate receiving when used on the customer side, which is beneficial to realize the low-cost and easy-to-operate 50GPON optical module.

[0008] The first purpose of the present application is to provide an avalanche photodetector structure with adjustable receiving rate, and the technical solution is as follows:

[0009] An avalanche photodetector structure with adjustable receiving rate includes an APD composed of a positive electrode layer, an absorption layer, a gain layer, a substrate layer and a negative electrode layer, the gain layer includes a charge control region and an avalanche multiplication region, and the negative electrode layer includes only one negative electrode; further comprising a plurality of multiplication control regions, at least one additional avalanche multiplication region and corresponding additional negative electrodes, the multiplication control regions and the additional avalanche multiplication regions are located in the gain layer, the avalanche multiplication regions are independently arranged, the negative electrodes are independently arranged, and the multiplication control regions, the avalanche multiplication regions and the negative electrodes are one-to-one corresponding; the multiplication control regions and the charge control region act alone or jointly to realize the regulation of two or more avalanche multiplication regions.

[0010] Further preferably, the multiplication control regions and the independent negative electrodes are formed by ion implantation or selective doping in the avalanche photodetector. Without increasing additional process steps, the present application can increase the independent multiplication control regions.

[0011] Further preferably, the independent multiplication control regions generate independent avalanche multiplication regions. The independent avalanche multiplication regions can control the total gain of the APD in the working state, and the gain changes at the same time, so that the APD receiving rate can be adjusted.

[0012] Further optimization involves a one-to-one correspondence between the negative electrode and the avalanche multiplication region, with the negative electrode controlling the on / off state of the avalanche multiplication region. By controlling the voltage of the negative electrode, the gain of the avalanche multiplication region can be precisely adjusted, thus allowing for more flexible control of the APD rate.

[0013] The second objective of this invention is to provide an avalanche photodetector with adjustable reception rate, achieved through the fabrication of a structure for an avalanche photodetector with adjustable reception rate, including...

[0014] The substrate includes two independent N-type electrode injection regions, I and II, which are respectively connected to negative electrode I and negative electrode II.

[0015] The gain layer is used to form mutually independent avalanche multiplication regions I and II. The gain layer includes a charge control region and mutually independent multiplication control regions I and II. The charge control region is located above the multiplication control region.

[0016] The absorption layer is located above the gain layer;

[0017] The positive electrode layer, located above the absorber layer, includes a P-type doped implantation layer and a positive electrode region.

[0018] Further preferably, the positive electrode layer is obtained by directly doping the absorber layer or by growing a separate epitaxial material; the positive electrode layer is connected to the positive electrode through a metal layer.

[0019] In a further preferred embodiment, the gain layer also includes a guard ring injection layer, which is located around the charge control region.

[0020] The third objective of this invention is to propose an avalanche photodetector with adjustable receiving rate, wherein the technical solution adopted is as follows: the avalanche photodetector structure with adjustable receiving rate is fabricated, including...

[0021] The substrate includes two independent N-type electrode injection regions, I and II, which are connected to negative electrode I and negative electrode II, respectively; a waveguide structure is etched on the top layer of the substrate.

[0022] The gain layer is used to form mutually independent avalanche multiplication regions I and II. The gain layer includes a charge control region and mutually independent multiplication control regions I and II. The charge control region is located above the multiplication control region.

[0023] The absorption layer is located above the gain layer;

[0024] The positive electrode layer, located above the absorber layer, includes a P-type doped implantation layer and a positive electrode region.

[0025] Further optimization involves setting the multiplication control region I and the multiplication control region II independently along the waveguide structure direction or independently along the direction perpendicular to the waveguide structure.

[0026] Further optimization involves coupling the input signal light with the waveguide structure to form a waveguide mode.

[0027] The advantages of this invention compared to the prior art are as follows:

[0028] The avalanche photodetector of the present invention has an adjustable receiving rate, and the APD gain can be adjusted over a wide range to achieve two levels of adjustment: low bandwidth high gain and high bandwidth low gain, which can be used to receive optical signals of different rates. Attached Figure Description

[0029] Figure 1 It is a traditional APD design drawing;

[0030] Figure 2 This is a design diagram of the multi-rate reception APD proposed in this invention;

[0031] Figure 3 This is the epitaxial structure design diagram of the multi-rate receiving APD in Example 1;

[0032] Figure 4 This is a front electrode design diagram of the multi-rate accepting APD in Example 1;

[0033] Figure 5 This is the epitaxial structure design diagram of the multi-rate receiving APD in Example 2;

[0034] Figure 6 This is a front electrode design diagram of the first gain region controlled ion implantation distribution scheme of the multi-rate accepting APD in Example 2.

[0035] Figure 7 This is a front electrode design diagram of the second gain region controlled ion implantation distribution scheme of the multi-rate accepting APD in Example 2.

[0036] Wherein, 1 is negative electrode I, 2 is negative electrode II, and 3 is positive electrode;

[0037] 10 is the substrate layer, 20 is the gain layer, 20-1 is the avalanche multiplication region, 20-2 is the multiplication control region, 30 is the absorption layer, 40 is the positive electrode layer, 60 is the waveguide structure, 70 is the negative electrode layer, and 70-1 is the negative electrode.

[0038] 101 is N-type electrode injection region I, and 102 is N-type electrode injection region II;

[0039] 201 is the multiplication control region I, 202 is the multiplication control region II, 203 is the protective ring injection layer, and 204 is the charge control region;

[0040] 501 is avalanche multiplication zone I, and 502 is avalanche multiplication zone II. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figures 1-7 The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] The avalanche photodetector structure with adjustable receiving rate proposed in this embodiment, such as Figure 2 As shown. From top to bottom, it includes: a positive electrode layer 40, an absorption layer 30, a gain layer 20, a substrate layer 10, and a negative electrode layer 70. The gain layer 20 includes two multiplication control regions 20-2, a charge control region 204, and two avalanche multiplication regions 20-1. The negative electrode layer 70 includes two negative electrodes 70-1. Compared to conventional APD designs, such as... Figure 1 As shown, compared to the previous version, two multiplication control regions 20-2, one avalanche multiplication region 20-1, and a corresponding negative electrode 70-1 were added. Through the individual or combined action of the multiplication control region 20-2 and the charge control region 204, the regulation of two or more avalanche multiplication regions can be achieved.

[0043] In an avalanche photodetector with adjustable acceptance rate, independent multiplication control regions and independent negative electrodes are formed through ion implantation or selective doping. These independent multiplication control regions generate independent avalanche multiplication regions. The negative electrodes are configured in a one-to-one correspondence with the avalanche multiplication regions, controlling the on / off state of the avalanche multiplication regions.

[0044] When receiving a 50Gbps rate, only one of the negative electrodes I1 and II2 is used, and the APD operates in a low-gain, high-bandwidth state. When receiving a 25Gbps rate, both negative electrodes I1 and II2 are turned on, and the APD operates in a high-gain, low-bandwidth state.

[0045] Based on this design, and combined with the switching on and off of external electrodes, the multi-rate APD of this embodiment can be applied to the reception of optical signals at different rates.

[0046] Example 1

[0047] This embodiment utilizes an avalanche photodetector structure with adjustable receiving rate to fabricate a surface-incident multi-rate APD. The input signal light A directly illuminates the photosensitive area, such as...Figure 3 , Figure 4 As shown.

[0048] An epitaxial structure design for a surface-incident multi-rate APD, such as... Figure 3 As shown, it includes: a substrate layer 10, a gain layer 20, an absorption layer 30, and a positive electrode layer 40.

[0049] The substrate 10 includes two independent N-type electrode injection regions I 101 and II 102, which are respectively connected to negative electrode I 1 and negative electrode II 2.

[0050] The material of the substrate layer 10 is not limited, and the materials that can be selected include bulk silicon, SOI or compound semiconductor InP, etc.

[0051] The implanted ions in N-type electrode implantation region I 101 and N-type electrode implantation region II 102 may include (As) or phosphorus (P).

[0052] like Figure 3 As shown, the gain layer 20 includes: a charge control region 204, a guard ring injection layer 203, and two independent multiplication control regions I 201 and II 202, with the charge control region 204 located above the multiplication control regions.

[0053] Both the doubling control region I 201 and the doubling control region II 202 are N-type injections.

[0054] The protective ring implantation layer 203 is located around the charge control region 204 and is achieved through P-type ion implantation. Its function is to provide electric field protection on the outside of the absorption layer and reduce leakage current on the outside of the absorption layer.

[0055] The function of gain layer 20 is to form multiple independent avalanche multiplication regions, such as Figure 3 As shown, in this embodiment, the gain layer 20 serves to form mutually independent avalanche multiplication regions I 501 and II 502. The size (height) of the avalanche multiplication regions is determined by the height difference between the multiplication control regions I 201 and II 202 and the charge control region 204. The size (height) of the avalanche multiplication regions determines the gain that these regions can provide.

[0056] Optionally, the areas and sizes of the multiplication control region I 201 and the multiplication control region II 202 can be different; that is, the areas of the avalanche multiplication region I 501 and the avalanche multiplication region II 502 can be adjusted separately by implanting the multiplication control region I 201 and the multiplication control region II 202. Alternatively, multiple ion implantations or adjustments to the ion implantation energy can be used to control the size (height) of the multiplication control region I 201 and the multiplication control region II 202.

[0057] The absorption layer 30 is used to absorb the input signal light A to generate a photocurrent. The material of the absorption layer 30 can be InGaAs, Ge, GeSi and GeSn, etc.

[0058] The positive electrode layer 40 includes a P-type doped implantation layer and a positive electrode region. The positive electrode is a single unit and does not need to be distinguished separately. The positive electrode layer 40 can be obtained by directly doping the absorber layer 30, or it can be obtained by growing a separate epitaxial material, such as a-Si material.

[0059] The front electrode design of the planar incident multi-rate APD in this embodiment is as follows: Figure 4 As shown.

[0060] The independent N-type electrode injection regions Ⅰ101 and Ⅱ102 are semi-annular injections, and are connected to the negative electrode Ⅰ1 and the negative electrode Ⅱ2 respectively through a metal layer.

[0061] The absorption layer 30 is circular, and the top positive electrode layer 40 is above the absorption layer 30. The positive electrode layer 40 is connected to the positive electrode 3 through a metal layer.

[0062] Both the multiplication control region I 201 and the multiplication control region II 202 are semi-circular injection regions. A non-injection region is left in the middle of the injection regions of the multiplication control region I 201 and the multiplication control region II 202. The size of the non-injection region depends on the manufacturing precision of the semiconductor processing technology, and is generally 1~2um.

[0063] In this embodiment, the multiplication control region I 201 and the multiplication control region II 202 of the surface-incident multi-rate APD are arranged perpendicular to the incident input signal light A. Furthermore, in this embodiment, the surface-incident multi-rate APD can only be used as an independent chip.

[0064] Optionally, in this embodiment, by setting three multiplication control regions and correspondingly setting three N-type electrode injection regions and three negative electrodes, the gain of the surface-incident multi-rate APD in this embodiment can be more accurately controlled. Considering the complexity of APD packaging, two multiplication control regions are more conducive to actual production needs.

[0065] Example 2

[0066] This embodiment employs an avalanche photodetector structure with adjustable receiving rate to fabricate a waveguide-guided multi-rate APD. The input signal light A is coupled through a waveguide, forming a waveguide mode, and is gradually absorbed by the APD. Figure 5 , Figure 6 , Figure 7 As shown.

[0067] The epitaxial structure design of the waveguide radiation multi-rate APD in this embodiment is as follows: Figure 5As shown, the epitaxial structure of the waveguide multi-rate APD is the same as that of the surface-incident APD in Example 1 in the vertical direction, both including: substrate layer 10, gain layer 20, absorption layer 30 and positive electrode layer 40.

[0068] The difference is that, for example Figure 5 As shown, a waveguide structure 60 is etched on the top layer of the substrate 10. The substrate 10 can be made of Si or an InP compound. Furthermore, the substrate 10 and the waveguide structure 60 are made of the same material.

[0069] The front electrode design of the waveguide-guided multi-rate APD in this embodiment is as follows: Figure 6 As shown.

[0070] The absorption layer 30 is rectangular, realizing the optical waveguide mode and generating photocurrent.

[0071] The independent N-type electrode injection regions Ⅰ101 and Ⅱ102 are located on both sides of the absorption layer 30 and are connected to the negative electrodes Ⅰ1 and Ⅱ2 through a metal layer.

[0072] The positive electrode layer 40 is located above the absorption layer 30 and is connected to the positive electrode 3 through a metal layer.

[0073] In this embodiment of the waveguide radiation multi-rate APD, negative electrode I1 and negative electrode II2 can be located on the same side of the chip as positive electrode 3.

[0074] The doubling control region I 201 and the doubling control region II 202 are formed by independent ion implantation. The spacing between the doubling control region I 201 and the doubling control region II 202 can be determined based on the semiconductor process capability. The doubling control region I 201 and the doubling control region II 202 are connected to the N-type electrode implantation region I 101 and the N-type electrode implantation region II 102, respectively, to achieve independent adjustment of the doubling region gain.

[0075] like Figure 6 As shown, in the first gain control method, the multiplication control region I 201 and the multiplication control region II 202 are set independently along the vertical direction of the waveguide structure 60.

[0076] like Figure 7 As shown, in the second gain control method, the multiplication control region I 201 and the multiplication control region II 202 are set independently along the waveguide structure 60 direction.

[0077] In this embodiment, the waveguide radiation multi-rate APD can be used as a standalone chip or integrated on the same substrate 10 and connected to other chips on the substrate 10. Its input signal light A can be the input light from other chips.

[0078] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tunable avalanche photodetector structure, comprising an APD, the APD being composed of a positive electrode layer (40), an absorption layer (30), a gain layer (20), a substrate layer (10), and a negative electrode layer (70), wherein the gain layer (20) includes a charge control region (204) and an avalanche multiplication region (20-1), and the negative electrode layer (70) includes only one negative electrode (70-1); characterized in that, It also includes multiple multiplication control regions (20-2), at least one additional avalanche multiplication region (20-1), and a corresponding additional negative electrode (70-1). The multiplication control region (20-2) and the additional avalanche multiplication region (20-1) are both located within the gain layer (20). The avalanche multiplication region (20-1) is set independently of each other, and the negative electrode (70-1) is set independently of each other. The multiplication control region (20-2), the avalanche multiplication region (20-1), and the negative electrode (70-1) are set in a one-to-one correspondence. The multiplication control region (20-2) and the charge control region (204) work individually or together to achieve the regulation of two or more avalanche multiplication regions (20-1).

2. The avalanche photodetector structure with adjustable receiving rate according to claim 1, characterized in that, The avalanche photodetector forms independent multiplication control regions and independent negative electrodes through ion implantation or selective doping.

3. The avalanche photodetector structure with adjustable receiving rate according to claim 1, characterized in that, Independent doubling control regions (20-2) generate independent avalanche doubling regions (20-1).

4. The avalanche photodetector structure with adjustable receiving rate according to claim 1, characterized in that, The negative electrode (70-1) is set in a one-to-one correspondence with the avalanche multiplication zone (20-1), and the negative electrode (70-1) controls the on / off state of the avalanche multiplication zone (20-1).

5. An avalanche photodetector with adjustable receiving rate, characterized in that, The avalanche photodetector structure with adjustable acceptance rate according to any one of claims 1-4 is fabricated to include... The substrate (10) includes an independent N-type electrode injection region I (101) and an N-type electrode injection region II (102), which are respectively connected to negative electrode I (1) and negative electrode II (2). Gain layer (20) is used to form mutually independent avalanche multiplication region I (501) and avalanche multiplication region II (502). Gain layer (20) includes charge control region (204) and mutually independent multiplication control region I (201) and multiplication control region II (202). Charge control region (204) is located above multiplication control region. An absorption layer (30) is located above the gain layer (20); The positive electrode layer (40) is located above the absorber layer (30) and includes a P-type doped implantation layer and a positive electrode region.

6. The avalanche photodetector with adjustable receiving rate according to claim 5, characterized in that, The positive electrode layer (40) is obtained by direct doping in the absorption layer (30) or by growing a separate epitaxial material; the positive electrode layer (40) is connected to the positive electrode (3) through a metal layer.

7. The avalanche photodetector with adjustable receiving rate according to claim 5, characterized in that, The gain layer (20) also includes a guard ring injection layer (203) located around the charge control region (204).

8. An avalanche photodetector with adjustable receiving rate, characterized in that, The avalanche photodetector structure with adjustable acceptance rate according to any one of claims 1-4 is fabricated, including... The substrate (10) includes mutually independent N-type electrode injection regions I (101) and II (102), which are connected to negative electrode I (1) and negative electrode II (2), respectively; a waveguide structure (60) is formed by etching on the top layer of the substrate (10). Gain layer (20) is used to form mutually independent avalanche multiplication region I (501) and avalanche multiplication region II (502). Gain layer (20) includes charge control region (204) and mutually independent multiplication control region I (201) and multiplication control region II (202). Charge control region (204) is located above multiplication control region. An absorption layer (30) is located above the gain layer (20); The positive electrode layer (40) is located above the absorber layer (30) and includes a P-type doped implantation layer and a positive electrode region.

9. The avalanche photodetector with adjustable receiving rate according to claim 8, characterized in that, The multiplication control region I (201) and the multiplication control region II (202) are set independently along the direction of the waveguide structure (60) or independently along the direction perpendicular to the waveguide structure (60).

10. The avalanche photodetector with adjustable receiving rate according to claim 8, characterized in that, The input signal light (A) is coupled with the waveguide structure (60) to form a waveguide mode.

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