Avalanche photodetector chip and light receiving module
By designing an avalanche photodetector chip with a multi-layer optical receiver unit, the problems of complex structure and high cost of optical receiver module in Combo PON optical line terminal device were solved, realizing efficient reception and low-cost packaging of multi-wavelength signal light.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2026-03-13
AI Technical Summary
In the optical line terminal unit of Combo PON, the optical receiving modules with wavelengths of 1270nm and 1310nm are packaged together in TO packaging, resulting in a complex structure and high cost.
A new avalanche photodetector chip is designed, in which the absorption layer of the multi-layer light receiving unit gradually increases in size along the light transmission direction to achieve non-crosstalk between multi-wavelength signal light. The crosstalk risk is reduced by an electrical isolation layer and a distributed Bragg reflection structure, and the optical path structure is simplified.
This achieves a multi-receiver integration where multiple optical receiving units are integrated on the same chip without crosstalk, reducing the complexity and cost of the optical receiving module.
Smart Images
Figure CN121665706A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of photoelectric conversion technology, and in particular to avalanche photodetector chips and optical receiving modules. Background Technology
[0002] During the evolution or upgrade from Gigabit-Capable Passive Optical Network (GPON) access systems to 10G GPON, scenarios often arise where GPON and 10G GPON access coexist. To adapt to this coexistence scenario, Combo PON is typically employed. Combo PON is a PON network that supports multiple PON protocols.
[0003] In related technologies, the optical line terminal (OLT) device of Combo PON includes two optical receiving modules with wavelengths of 1270nm and 1310nm, and two optical transmitting modules with wavelengths of 1490nm and 1577nm. The two optical receiving modules are usually packaged in a transistor outline (TO) package. Isolators and filters need to be set for each optical receiving module. In addition, a beam splitter is also required to achieve optical path separation. This makes the TO package structure of the optical receiving module relatively complex and costly.
[0004] Public content
[0005] This disclosure provides an avalanche photodetector chip and a light receiving module, which can solve the technical problems existing in related technologies. The technical solution is as follows.
[0006] On the one hand, an avalanche photodetector chip is provided, the avalanche photodetector chip comprising: a multilayer light receiving unit arranged sequentially along the light transmission direction, each light receiving unit comprising a P-type contact layer, an N-type contact layer, and an absorption layer, a charge layer, and a multiplication layer stacked between the P-type contact layer and the N-type contact layer;
[0007] Along the light transmission direction, the absorption wavelength of the multiple absorption layers of the multilayer light receiving unit gradually increases.
[0008] The avalanche photodetector chip provided in this disclosure achieves non-interference reception of multi-wavelength signal light by gradually increasing the absorption wavelength of multiple absorption layers in a multi-layer optical receiving unit along the light transmission direction. This allows the multi-layer optical receiving unit to sequentially absorb multiple signal lights with increasing wavelengths along the light transmission path, enabling the avalanche photodetector chip to receive multi-wavelength signal light without crosstalk. Furthermore, this avalanche photodetector chip integrates multiple optical receiving units onto a single chip, achieving a unified reception form where multiple optical receiving units on a single chip do not interfere with each other in photoelectric response. The avalanche photodetector chip can be packaged into an optical receiving module in a TO package, reducing the number of complex wavelength division structures, filters, and other optical components used, simplifying the optical path structure and mechanical packaging structure of the optical receiving module, and lowering costs.
[0009] In some possible implementations, at least two adjacent optical receiving units in the multilayer optical receiving unit have an electrical isolation layer to provide electrical isolation between the adjacent optical receiving units.
[0010] By setting an electrical isolation layer, the two adjacent light receiving units are electrically isolated, thereby ensuring that the ohmic electrodes on the two light receiving units are independent and significantly reducing the risk of crosstalk in the photoelectric response of the two light receiving units.
[0011] In some examples, the electrical isolation layer is provided between any two adjacent optical receiving units in the multilayer optical receiving unit, so that each multilayer optical receiving unit is independent.
[0012] In some possible implementations, at least some adjacent optical receiving units in the multilayer optical receiving unit share the P-type contact layer or the N-type contact layer.
[0013] In some possible implementations, at least two adjacent layers of the multilayer optical receiving unit have a distributed Bragg reflection structure. This structure reflects light with wavelengths less than a wavelength threshold and transmits light with wavelengths greater than the wavelength threshold. Reflecting smaller wavelengths upstream of the distributed Bragg reflection structure and transmitting larger wavelengths downstream of it is more advantageous for enhancing the absorption efficiency of the optical receiving units on either side of the structure for their respective wavelengths.
[0014] In some possible implementations, the avalanche photodetector chip includes an electrically isolated layer for isolating two adjacent light receiving units, and the distributed Bragg reflection structure is disposed on the electrically isolated layer.
[0015] In some examples, at least two adjacent optical receiving units in the multilayer optical receiving unit share the P-type contact layer or the N-type contact layer, and the distributed Bragg reflection structure is provided on the shared P-type contact layer or N-type contact layer.
[0016] In some possible implementations, the avalanche photodetector chip further includes an anti-reflection layer disposed on the light-incident side of the multilayer light receiving unit.
[0017] By setting an antireflection film on the light-incident side of the multilayer light receiving unit, reflected light is reduced, transmitted light is increased, the transmittance of light on the chip surface is improved, and the light extraction efficiency of the chip is increased.
[0018] In some possible implementations, the optical receiving unit is configured as two, three, or four layers stacked together.
[0019] On the other hand, an optical receiving module is provided, the optical receiving module comprising: a TO package housing and an avalanche photodetector chip located inside the TO package housing, wherein the avalanche photodetector chip is as described in any of the above descriptions. Attached Figure Description
[0020] Figure 1 A schematic diagram of the structure of an exemplary avalanche photodetector chip provided in this disclosure embodiment;
[0021] Figure 2 for Figure 1 The diagram shows one arrangement of the functional layers in an avalanche photodetector chip.
[0022] Figure 3 A schematic diagram showing the light absorption ratio distribution of various semiconductor materials at different wavelengths provided in the embodiments of this disclosure;
[0023] Figure 4 for Figure 1 The diagram shows another arrangement of the functional layers in the avalanche photodetector chip.
[0024] Figure 5 This is a schematic diagram of the structure of another exemplary avalanche photodetector chip provided in this embodiment of the disclosure;
[0025] Figure 6 This is a schematic diagram of the structure of another exemplary avalanche photodetector chip provided in the embodiments of this disclosure;
[0026] Figure 7 A schematic diagram of the structure of another exemplary avalanche photodetector chip provided in this disclosure embodiment;
[0027] Figure 8This is a schematic diagram showing the transmittance distribution of various light-transmitting materials at different wavelengths, as provided in the embodiments of this disclosure.
[0028] in, Figure 3 The bottom horizontal axis, Wavelength, represents the incident wavelength; the vertical axis, α, represents the light absorption ratio; and the top horizontal axis, Photon energy, represents the photon energy.
[0029] The reference numerals in the attached figures represent:
[0030] 100. Optical receiving unit; 1001. First optical receiving unit; 1002. Second optical receiving unit; 1003. Third optical receiving unit;
[0031] 11. P-type contact layer; 12. N-type contact layer; 13. Absorption layer; 14. Charge layer; 15. Multiplication layer;
[0032] 110, P-ohm electrode; 120, N-ohm electrode;
[0033] 200. Electrical isolation layer;
[0034] 300. Distributed Bragg reflection structure;
[0035] 400. Anti-reflective coating. Detailed Implementation
[0036] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.
[0037] In the description of the embodiments of this disclosure, it should be understood that the terms "axial", "radial", "length", "width", "thickness", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.
[0038] Passive Optical Network (PON), based on wavelength division multiplexing (WDM) technology, is an optical access network technology that mainly includes an Optical Line Terminal (OLT), an Optical Network Unit (ONU), and an Optical Distribution Network (ODN).
[0039] During the evolution or upgrade from Gigabit-Capable Passive Optical Network (GPON) access systems to 10G GPON, scenarios often arise where GPON and 10G GPON access coexist. To adapt to this coexistence scenario, Combo PON is typically employed. Combo PON is a PON network that supports multiple PON protocols.
[0040] In related technologies, the optical line terminal (OLT) device of Combo PON includes two optical receiving modules with wavelengths of 1270nm and 1310nm. The two optical receiving modules are usually packaged together in the form of transistor outline (TO). However, the TO packaging structure of the dual-receiver optical receiving module is more complex and has a higher cost.
[0041] To address this technical problem, this disclosure provides an avalanche photodetector chip with a multi-in-one receiver design, as shown in the attached figure. Figure 1 As shown, the avalanche photodetector chip integrates multiple optical receiving units 100 to simplify the TO packaging structure of the optical receiving module.
[0042] It should be noted that an avalanche photodiode (APD) is a high-sensitivity photodetector that converts light signals into electrical signals. In the receiving end of an optical communication system, a highly sensitive avalanche photodetector chip, i.e., an APD chip, is typically used to capture the weak light signals from the optical transmission terminal.
[0043] The working principle of an APD chip is as follows: When photons irradiate a semiconductor absorbing material, they are absorbed and photogenerated carriers (i.e., electron-hole pairs) are generated. Holes move towards the P-region and electrons move towards the N-region. Under reverse bias voltage conditions, due to the effect of the electric field, when electrons and holes meet, secondary electrons are generated, forming an avalanche effect. That is, the photogenerated carriers avalanche multiply in the electric field region, forming a large photocurrent and realizing photoelectric conversion.
[0044] The avalanche photodetector chip disclosed in this embodiment includes multiple layers of light receiving units 100 arranged sequentially along the light transmission direction, as further shown in the attached figure. Figure 2 As shown, each optical receiving unit 100 includes a P-type contact layer 11, an N-type contact layer 12, and an absorption layer 13, a charge layer 14, and a multiplication layer 15 stacked between the P-type contact layer 11 and the N-type contact layer 12. Along the light transmission direction, the absorption wavelength of the multiple absorption layers 13 of the multilayer optical receiving unit 100 gradually increases.
[0045] The absorption layer 13 absorbs signal light of a specific wavelength to generate photogenerated carriers. The charge layer 14 transfers the photogenerated carriers to the multiplication layer 15 and creates a strong electric field in the multiplication layer 15, allowing the carriers to multiply. The multiplication layer 15 ionizes the photogenerated carriers that drift into the electric field through collisions, resulting in avalanche multiplication and increasing the number of carriers to amplify the signal. The movement of carriers generates an electrical signal between the P-type contact layer 11 and the N-type contact layer 12. A P-ohm electrode 110 is disposed on the P-type contact layer 11, and an N-ohm electrode 120 is disposed on the N-type contact layer 12. The P-ohm electrode 110 and the N-ohm electrode 120 are used for outputting the electrical signal.
[0046] In combination with any of the avalanche photodetector chips mentioned above, the number of light receiving units 100 can be multiple. For example, the number of light receiving units 100 can be 2-10. In some examples, the light receiving units 100 are arranged in two, three, or four layers. Correspondingly, the avalanche photodetector chip can be a dual-receiver-in-one, triple-receiver-in-one, or quadruple-receiver-in-one chip.
[0047] The avalanche photodetector chip provided in this embodiment has an avalanche photodetector chip in which the absorption wavelengths of the multiple absorption layers 13 of the multilayer light receiving unit 100 gradually increase along the light transmission direction. That is, along the light transmission path, the absorption wavelengths of the multilayer light receiving unit 100 increase sequentially, thereby absorbing multiple signal lights with wavelengths ranging from small to large. For example, when multiple wavelengths of signal light are simultaneously incident on the avalanche photodetector chip, along the light transmission direction, the signal light with the smallest wavelength is first absorbed and multiplied by the light receiving unit 100 with the smallest absorption wavelength, while the signal light with a larger wavelength passes through "transparently" and is absorbed by the other light receiving units 100 that follow. This process continues along the light transmission path; as the absorption wavelength of the signal light gradually increases, the signal light with a smaller wavelength is absorbed and multiplied by its corresponding light receiving unit 100 before the signal light with a larger wavelength, and finally, the signal light with the largest wavelength is absorbed and multiplied by the light receiving unit 100 with the largest absorption wavelength.
[0048] In summary, the avalanche photodetector chip provided in this embodiment achieves non-interference reception of multi-wavelength signal light by gradually increasing the absorption wavelength of the multiple absorption layers 13 of the multi-layer optical receiving unit 100 along the light transmission direction. This allows the multi-layer optical receiving unit 100 to sequentially absorb multiple signal lights with increasing wavelengths along the light transmission path, enabling the avalanche photodetector chip to receive multi-wavelength signal light without crosstalk. Furthermore, the avalanche photodetector chip integrates multiple optical receiving units 100 onto a single chip, achieving a unified reception form where multiple optical receiving units 100 on a single chip do not interfere with each other in photoelectric response. This avalanche photodetector chip can be packaged into an optical receiving module in a TO package, reducing the number of complex wavelength division structures, filters, and other optical components used, simplifying the optical path structure and mechanical packaging structure of the optical receiving module, and lowering costs.
[0049] In this embodiment, by changing the absorption wavelength of the multiple absorption layers 13 of the multilayer optical receiving unit 100, targeted reception of signal light of multiple wavelengths on the same optical path can be achieved. The material used in the absorption layer 13 is usually called an absorbing material, which is usually a semiconductor material. The working principle of a semiconductor material is as follows: when light irradiates a semiconductor material, if the energy of the photon is equal to or greater than the band gap (i.e., band gap Eg) of the semiconductor material, electrons in the valence band absorb the photon energy and jump to the conduction band, generating electron-hole pairs (i.e., photogenerated carriers). When the absorbing material is used in a semiconductor device with a PN junction, under the action of the built-in electric field, electrons drift to the N region and holes drift to the P region. When the external circuit of the PN junction forms a loop, a photocurrent can be formed.
[0050] When the absorbing material is typically a semiconductor compound (e.g., an alloy material), since the semiconductor compound contains multiple elements, the energy band of the semiconductor compound can be adjusted by changing the atomic percentage of each element, or by further doping the semiconductor compound with other elements, thereby adjusting its absorption wavelength.
[0051] To verify the above conclusions, simulation tests were conducted on the absorption wavelengths of various materials in the embodiments of this disclosure. The test results are shown in [reference needed]. Figure 1 , Figure 3 Examples are given of the absorption wavelengths of some elements (e.g., Sj, Ge), whose absorption wavelengths are not adjustable. In contrast, Figure 3 Examples of absorption wavelengths for some semiconductor compounds are also given, such as GaAs compounds, and InGaAs compounds obtained by doping GaAs compounds with In (e.g., Figure 3 The In shown 0.53 Ga 0.47As, where each subscript represents an atomic percentage), InGaAsP compounds obtained by doping GaAs compounds with In and P elements (e.g., ... Figure 3 The In shown 0.7 Ga 0.3 As 0.64 P 0.36 As can be seen, by doping GaAs compounds with In, the absorption wavelength of the resulting InGaAs compounds is changed compared to that of GaAs compounds. Similarly, by doping GaAs compounds with In and P, the absorption wavelength of the resulting InGaAsP compounds is also changed compared to that of GaAs compounds.
[0052] In some examples, the gradient difference in absorption wavelength between the absorption layers 13 in two adjacent light receiving units 100 can be 10nm-100nm, and further, it can be 10nm-50nm, including but not limited to: 10nm, 20nm, 30nm, 40nm, 50nm, etc.
[0053] For example, in an avalanche photodetector chip with a dual-receiver-in-one orthogonal incidence structure, the absorption layer 13 of the upper light receiving unit 100 can absorb wavelengths of 1300 nm. This layer can block signal light with wavelengths less than 1300 nm, such as 1270 nm ± 10 nm, while allowing signal light with wavelengths greater than 1300 nm to pass through transparently, such as 1310 nm ± 10 nm. The absorption layer 13 of the lower light receiving unit 100 can absorb wavelengths of 1330 nm, blocking signal light with wavelengths less than 1330 nm, such as 1310 nm ± 10 nm. This makes the avalanche photodetector chip suitable for receiving light with wavelengths of 1270 nm and 1310 nm.
[0054] This disclosure also includes spectral response simulation tests of InGaAsP semiconductor materials using known Separate Absorption Gradient Charge Multiplication (SAGCM) and PIN structure chips. Both used InGaAsP semiconductor materials with an absorption wavelength of 1300 nm. Simulation results showed that both chip structures exhibited the following characteristics: when the wavelength is greater than 1300 nm, the chip's wavelength absorption responsivity is extremely low, close to 0, at which point the incident light does not undergo photoelectric conversion. When the wavelength is less than 1300 nm, the chip's wavelength absorption responsivity is high, and the incident light can undergo photoelectric conversion.
[0055] Taking a SAGCM structure chip as an example, at an operating voltage of 15V, its wavelength absorption responsivity rejection ratio (i.e., the light responsivity when the wavelength is less than 1300nm / the light responsivity when the wavelength is greater than 1300nm) is as high as 1.23×10⁻⁶. 5 At an operating voltage of 30V, its wavelength absorption responsivity rejection ratio is as high as 1.14 × 10⁻⁶. 5 At an operating voltage of 36V, its wavelength absorption responsivity rejection ratio is as high as 7.44×10⁻⁶. 4 At an operating voltage of 40V, its wavelength absorption responsivity rejection ratio is as high as 1.70×10⁻⁶. 5 Taking a PIN-structured chip as an example, at an operating voltage of 15V, its wavelength absorption responsivity rejection ratio is as high as 2.03 × 10⁻⁶. 5 It can be assumed that the absorption responsivity rejection ratio for wavelengths less than 1300 nm and greater than 1300 nm is >40 dB. This indicates that InGaAsP semiconductor materials with an absorption wavelength of 1300 nm efficiently cut off signal light with wavelengths less than 1300 nm, while allowing signal light with wavelengths greater than 1300 nm to pass through "transparently." This further confirms that by using absorbing materials with different absorption wavelengths, it is possible to absorb light with wavelengths less than their absorption wavelength and allow light with wavelengths greater than their absorption wavelength to pass through.
[0056] For the multiple absorption layers 13 involved in the embodiments of this disclosure, since the multiple light receiving units 100 are obtained by epitaxy on the same substrate, it is desirable for the lattice matching of each layer in the multiple light receiving units 100 to avoid interlayer mismatch and reduce dark current and carrier accumulation caused by lattice mismatch. Therefore, the multiple absorption materials used in the multiple absorption layers 13 can be prepared based on the same target semiconductor compound. For example, when the avalanche photodetector chip is prepared based on a group III-V compound, the absorption material of each absorption layer 13 can be adjusted based on the InGaAs compound by adjusting the atomic percentage and doping elements.
[0057] Regarding the avalanche photodetector chip mentioned above, see attached... Figure 1 As shown, an electrical isolation layer 200 can be provided between at least some of the adjacent optical receiving units 100 in the multilayer optical receiving unit 100, so that the two adjacent optical receiving units 100 are electrically isolated.
[0058] By setting an electrical isolation layer 200, the two adjacent light receiving units 100 are electrically isolated, thereby ensuring that the ohmic electrodes on the two light receiving units 100 are independent and significantly reducing the risk of crosstalk between the two light receiving units 100 in photoelectric response.
[0059] The insulating material used in the electrical isolation layer 200 can be consistent with the contact material type used in the P-type contact layer 11 and the N-type contact layer 12 to ensure interlayer lattice compatibility. For example, when the contact materials used in the P-type contact layer 11 and the N-type contact layer 12 are both InP materials, the electrical isolation layer 200 can also use InP materials. By doping it with Fe elements, a semi-insulating InP(Fe) material is formed and used as the insulating material of the electrical isolation layer 200.
[0060] In some examples, an electrical isolation layer 200 can be provided between any two adjacent optical receiving units 100 in the multilayer optical receiving unit 100, so that each of the multilayer optical receiving units 100 is independent. This scheme is suitable for situations where the multilayer optical receiving units 100 operate simultaneously without interfering with each other, so that the working mode of the avalanche photodetector chip can be multiplexed single-chip.
[0061] Taking an avalanche photodetector chip with a three-in-one normal incidence structure as an example, as shown in the attached... Figure 5 As shown, it includes a first light receiving unit 1001, a second light receiving unit 1002, and a third light receiving unit 1003 arranged sequentially from top to bottom, with the receiving wavelengths of the first light receiving unit 1001, the second light receiving unit 1002, and the third light receiving unit 1003 increasing sequentially. An electrical isolation layer 200 is disposed between the first light receiving unit 1001 and the second light receiving unit 1002, and another electrical isolation layer 200 is disposed between the second light receiving unit 1002 and the third light receiving unit 1003. The isolation materials of these two electrical isolation layers 200 can be the same. The first optical receiving unit 1001 has P-type contact layer 11 and N-type contact layer 12 respectively provided with P-ohm electrode 110 and N-ohm electrode 120, the second optical receiving unit 1002 has P-type contact layer 11 and N-type contact layer 12 respectively provided with P-ohm electrode 110 and N-ohm electrode 120, and the third optical receiving unit 1003 has P-type contact layer 11 and N-type contact layer 12 respectively provided with P-ohm electrode 110 and N-ohm electrode 120, so that the working mode of the avalanche photodetector chip can be three-way single-core.
[0062] In other examples, some adjacent optical receiving units 100 in the multilayer optical receiving unit 100 may have an electrical isolation layer 200 between them, while the remaining adjacent optical receiving units 100 may share a P-type contact layer 11 or an N-type contact layer 12. When sharing a P-type contact layer 11 or an N-type contact layer 12, the two optical receiving units 100 cannot operate simultaneously and can only operate one at a time. However, those optical receiving units isolated by the electrical isolation layer 200 can operate simultaneously without interfering with each other.
[0063] As can be seen from the above, in the embodiments of this disclosure, at least some of the adjacent optical receiving units 100 in the multilayer optical receiving unit 100 can share a P-type contact layer 11 or an N-type contact layer 12.
[0064] Continuing with the example of an avalanche photodetector chip with a three-in-one orthogonal incident structure, as shown in the attached... Figure 6 As shown, it includes a first light receiving unit 1001, a second light receiving unit 1002, and a third light receiving unit 1003 arranged sequentially from top to bottom, with the receiving wavelengths of the first light receiving unit 1001, the second light receiving unit 1002, and the third light receiving unit 1003 increasing sequentially. An electrical isolation layer 200 is disposed between the first light receiving unit 1001 and the second light receiving unit 1002, and the second light receiving unit 1002 and the third light receiving unit 1003 share an N-type contact layer 12. A P-ohm electrode 110 and an N-ohm electrode 120 are respectively disposed on the P-type contact layer 11 and the N-type contact layer 12 of the first light receiving unit 1001, respectively. A P-ohm electrode 110 is disposed on the P-type contact layer 11 of the second light receiving unit 1002 and the P-type contact layer 11 of the third light receiving unit 1003, respectively. An N-ohm electrode 120 is disposed on the N-type contact layer 12 shared by the second light receiving unit 1002 and the third light receiving unit 1003. In this configuration, one of the second optical receiving unit 1002 and the third optical receiving unit 1003 may operate, and one of the second optical receiving unit 1002 and the third optical receiving unit 1003 may operate simultaneously with the first optical receiving unit 1001.
[0065] In some other examples, any two adjacent optical receiving units 100 in the multilayer optical receiving unit 100 can share a P-type contact layer 11 or an N-type contact layer 12. This prevents these optical receiving units 100 from operating simultaneously, and only one can operate at a time. For example, when the optical receiving unit 100 is configured as two layers sharing a P-type contact layer 11 or an N-type contact layer 12, the avalanche photodetector chip can operate in simplex single-chip mode.
[0066] Continuing with the example of an avalanche photodetector chip with a three-in-one orthogonal incident structure, as shown in the attached... Figure 7As shown, it includes a first light receiving unit 1001, a second light receiving unit 1002, and a third light receiving unit 1003 arranged sequentially from top to bottom, with the receiving wavelengths of the first light receiving unit 1001, the second light receiving unit 1002, and the third light receiving unit 1003 increasing sequentially. The first light receiving unit 1001 and the second light receiving unit 1002 share an N-type contact layer 12, and the second light receiving unit 1002 and the third light receiving unit 1003 share a P-type contact layer 11. The P-type contact layer 11 of the first light receiving unit 1001 is provided with a P-ohm electrode 110, the N-type contact layer 12 shared by the first light receiving unit 1001 and the second light receiving unit 1002 is provided with an N-ohm electrode 120, the P-type contact layer 11 shared by the second light receiving unit 1002 and the third light receiving unit 1003 is provided with a P-ohm electrode 110, and the N-type contact layer 12 of the third light receiving unit 1003 is provided with an N-ohm electrode 120. Among them, one of the first optical receiving unit 1001, the second optical receiving unit 1002 and the third optical receiving unit 1003 can work at a time, and the three cannot work at the same time.
[0067] Regarding the avalanche photodetector chip mentioned above, see attached... Figures 1-2 As shown, a distributed Bragg reflection structure 300 can be provided between at least partially adjacent layers of optical receiving units 100 in the multilayer optical receiving unit 100. For example, a distributed Bragg reflection structure 300 can be provided between any two adjacent layers of optical receiving units 100 in the multilayer optical receiving unit 100. The distributed Bragg reflection structure 300 is used to reflect light with wavelengths less than a wavelength threshold range and transmit light with wavelengths greater than a wavelength threshold range. For the "wavelength threshold range" mentioned here, its lower limit is greater than the absorption wavelength of the optical receiving unit 100 upstream of the light transmission path, and its upper limit is less than the absorption wavelength of the optical receiving unit 100 downstream of the light transmission path.
[0068] The Distributed Bragg Reflector (DBR) structure can reflect light with wavelengths smaller than the wavelength threshold range and transmit light with wavelengths larger than the wavelength threshold range. In other words, it reflects smaller wavelengths of light upstream of the distributed Bragg reflector structure 300 and transmits larger wavelengths of light downstream of the distributed Bragg reflector structure 300. This is more beneficial for enhancing the light absorption efficiency of the light receiving units 100 on both sides of the distributed Bragg reflector structure 300 for their respective wavelengths.
[0069] The distributed Bragg reflection structure 300 can be a micromirror structure formed on the surface of a certain layer of the light receiving unit 100, obtained by etching the surface of a certain layer of the light receiving unit 100, thereby changing the optical properties of that layer.
[0070] In some examples, the avalanche photodetector chip includes an electrically isolated layer 200, which isolates two adjacent optical receiving units 100. The arrangement of the electrically isolated layer 200 can be found in the aforementioned schemes and will not be repeated here. (See attached...) Figures 1-2 As shown, a distributed Bragg reflection structure 300 can be formed on the electrically isolated layer 200. For example, the distributed Bragg reflection structure 300 can be obtained by etching on the surface of the electrically isolated layer 200 away from the substrate using an etching process.
[0071] by Figure 5 The avalanche photodetector chip shown is an example in which a distributed Bragg reflection structure 300 is provided on each electrical isolation layer 200.
[0072] In other examples, at least two adjacent optical receiving units 100 in the multilayer optical receiving unit 100 share a P-type contact layer 11 or an N-type contact layer 12, and a distributed Bragg reflection structure 300 may be provided on the shared P-type contact layer 11 or N-type contact layer 12.
[0073] by Figure 6 The avalanche photodetector chip shown is an example in which distributed Bragg reflector structures 300 are provided on both the electrical isolation layer 200 and the shared N-type contact layer 12.
[0074] Of course, it is not excluded that if the avalanche photodetector chip contains both an electrical isolation layer 200 and a shared P-type contact layer 11 or N-type contact layer 12, a distributed Bragg reflection structure 300 can be set on the electrical isolation layer 200, or a distributed Bragg reflection structure 300 can be set on the P-type contact layer 11 or N-type contact layer 12.
[0075] Combined with any of the avalanche photodetector chips mentioned above, as shown in the attached... Figures 1-2 As shown, the avalanche photodetector chip also includes an antireflection layer 400, which is disposed on the light-incident side of the multilayer light receiving unit 100. By disposing of the antireflection film on the light-incident side of the multilayer light receiving unit 100, reflected light is reduced, transmitted light is increased, the transmittance of light on the chip surface is improved, and the light extraction efficiency of the chip is increased.
[0076] In this embodiment, the avalanche photodetector chip can be a back-incident structure (the light-incident side is located on its back side) or a front-incident structure (the light-incident side is located on its front side). Based on the structure of the chip device, its light-incident side and photosensitive area are determined, thereby determining the position of the anti-reflection layer 400.
[0077] This disclosure also includes tests on the transmittance of some commonly used antireflective materials at different wavelengths, see [link to relevant documentation]. Figure 8 ,like Figure 8 As shown, the transmittance curves of SiN, Al3O2, and SiO2 materials remain flat and have very low variation over a wide wavelength range. This indicates that, based on some current antireflection materials, the transmittance wavelength range of the antireflection film can be very wide, that is, it can be adapted to multiple wavelengths, thus making it feasible to use one antireflection film to simultaneously handle multiple light receiving units 100.
[0078] In some examples, SiNx material, Al3O2 material, or SiO2 material can be used to form the antireflection layer 400 in the embodiments of this disclosure.
[0079] The avalanche photodetector chip involved in the embodiments of this disclosure can be an APD chip based on group III-V semiconductor materials. Accordingly, the materials of each layer can be selected from group III-V semiconductor materials.
[0080] For example, in an avalanche photodetector chip based on a III-V semiconductor material system, the material of the P-type contact layer 11 can be P-type InP (doped with elements such as Zn), the material of the N-type contact layer 12 can be N-type InP (doped with elements such as S, Sn), and the electrically insulating material can be a semi-insulating InP material with doped elements, such as Fe. The material of the multiplication layer 15 can be an i-type material based on InAlAs, and the material of the charge layer 14 can be a lightly doped P-type material or a lightly doped N-type material, such as InAlAs, InAlGaAs, InP, etc. The absorption materials corresponding to the multiple absorption layers 13 are all i-type materials based on InGaAs, such as InGaAs material, InGaAsP material, etc.
[0081] It is not excluded that the avalanche photodetector chip involved in the embodiments of this disclosure may also be based on other material systems, such as Ge / Si system materials, ultraviolet wide bandgap material systems (such as AlGaN system), etc.
[0082] For example, in an avalanche photodetector chip based on a Ge / Si material system, the P-type contact layer 11 can be made of P-type Si, the N-type contact layer 12 can be made of N-type Si, and the electrically insulating material can be an insulating Si-based material. The multiplication layer 15 can be made of i-Si material, the charge layer 14 can be made of p-Si material, and the absorption materials corresponding to the multiple absorption layers 13 are all based on i-Ge material.
[0083] A P-ohm electrode 110 is formed on the P-type contact layer 11, and the material of the P-ohm electrode 110 is selected from at least one of titanium, platinum, chromium, and gold. An N-ohm electrode 120 is formed on the N-type contact layer 12, and the material of the N-ohm electrode 120 may be, for example, gold or nickel.
[0084] It should be noted that the outermost P-type contact layer 11 or N-type contact layer 12 in the avalanche photodetector chip serves as a substrate. In addition, for each light receiving unit 100, the P-type contact layer 11, absorption layer 13, charge layer 14, multiplication layer 15, and N-type contact layer 12 can be stacked sequentially to form a PiPiN structure, or the P-type contact layer 11, multiplication layer 15, charge layer 14, absorption layer 13, and N-type contact layer 12 can be stacked sequentially to form a PiNiN structure. The embodiments disclosed herein do not limit the specific arrangements.
[0085] The thickness of each layer in the avalanche photodetector chip can be selected according to actual needs. Some exemplary solutions are as follows: the thickness of the P-type contact layer 11 and the N-type contact layer 12 can be 0.1μm-3μm, the thickness of the absorption layer 13 can be 0.1μm-5μm, the thickness of the charge layer 14 can be 0.01μm-1μm, the thickness of the multiplication layer 15 can be 0.01μm-3μm, etc.
[0086] Based on any of the avalanche photodetector chips mentioned above, the following example of a dual-receiver integrated avalanche photodetector chip will be used to further illustrate the arrangement of its layers.
[0087] Example 1
[0088] Example 1 provides a dual-collection integrated avalanche photodetector chip with an orthogonal incident structure, as shown in the attached figure. Figure 2 As shown, it includes an upper light receiving unit 100, an electrical isolation layer 200, and a lower light receiving unit 100 arranged sequentially along the light transmission direction. From top to bottom, the upper light receiving unit 100 includes a P-type contact layer 11, an absorption layer 13, a charge layer 14, a multiplication layer 15, and an N-type contact layer 12 arranged sequentially to form a PiPiN structure. Similarly, from top to bottom, the lower light receiving unit 100 includes the same P-type contact layer 11, absorption layer 13, charge layer 14, multiplication layer 15, and N-type contact layer 12, forming another PiPiN structure. A P-ohm electrode 110 and an N-ohm electrode 120 are respectively disposed on the P-type contact layer 11 and N-type contact layer 12 of the upper light receiving unit 100. The lower optical receiving unit 100 has P-ohm electrodes 110 and N-ohm electrodes 120 respectively disposed on the P-type contact layer 11 and N-type contact layer 12, so that the avalanche photodetector chip can adopt a duplex single-core working mode.
[0089] Specifically, the absorption wavelength of the absorption layer 13 in the upper light receiving unit 100 is smaller than that of the absorption layer 13 in the lower light receiving unit 100. For example, the absorption layer 13 in the upper light receiving unit 100 is InGaAsP with an absorption wavelength of 1300 nm, which can absorb signal light in a wavelength range of 1270 nm ± 10 nm and allows signal light in a wavelength range greater than 1310 nm ± 10 nm to "transparently pass through". The absorption layer 13 in the lower light receiving unit 100 is InGaAs with an absorption wavelength of 1330 nm, which can absorb signal light in a wavelength range of 1310 nm ± 10 nm. In this way, when two signal lights with wavelengths of 1270nm±10nm and 1310nm±10nm are simultaneously incident on the chip, the 1270nm±10nm signal light is first absorbed by the upper optical receiving unit 100, while the 1310nm±10nm signal light is then absorbed by the lower optical receiving unit 100, and the two optical receiving units 100 do not interfere with each other.
[0090] In addition, a distributed Bragg reflection structure 300 is provided on the electrical isolation layer 200 to increase the reflection of signal light with a wavelength of 1270nm and at the same time improve the transmission of signal light with a wavelength of 1310nm, thereby increasing the absorption efficiency of the light receiving unit 100 for the corresponding wavelength.
[0091] For the materials of other layers of the avalanche photodetector chip in Embodiment 1, the material of the P-type contact layer 11 can be P-type InP, the material of the N-type contact layer 12 can be N-type InP, the electrical isolation material can be a semi-insulating InP(Fe) material, the material of the multiplication layer 15 can be an i-type material based on InAlAs, and the material of the charge layer 14 can be a lightly doped P-type InAlAs or InP material.
[0092] Example 2
[0093] Example 2 provides a dual-collection integrated avalanche photodetector chip with an orthogonal incident structure, as shown in the attached figure. Figure 4As shown, it includes an upper light receiving unit 100 and a lower light receiving unit 100 arranged sequentially along the light transmission direction. From top to bottom, the upper light receiving unit 100 includes a P-type contact layer 11, an absorption layer 13, a charge layer 14, a multiplication layer 15, and an N-type contact layer 12 arranged sequentially to form a PiPiN structure. From top to bottom, the lower light receiving unit 100 includes an N-type contact layer 12, an absorption layer 13, a charge layer 14, a multiplication layer 15, and a P-type contact layer 11 arranged sequentially to form a NiNiP structure. As can be seen, the upper light receiving unit 100 and the lower light receiving unit 100 share an N-type contact layer 12, and an N-ohm electrode 120 is provided on the shared N-type contact layer 12. In addition, the P-type contact layer 11 of the upper light receiving unit 100 is provided with a P-ohm electrode 110, and the P-type contact layer 11 of the lower light receiving unit 100 is provided with a P-ohm electrode 110 and an N-ohm electrode 120, so that the avalanche photodetector chip can adopt a simplex single-core working mode.
[0094] Specifically, the absorption wavelength of the absorption layer 13 in the upper light receiving unit 100 is shorter than that in the lower light receiving unit 100. For example, the absorption layer 13 in the upper light receiving unit 100 is InGaAsP with an absorption wavelength of 1300nm, which can absorb signal light in the wavelength range of 1270nm±10nm and allows signal light in the wavelength range greater than 1310nm±10nm to "transparently pass through". The absorption layer 13 in the lower light receiving unit 100 is InGaAs with an absorption wavelength of 1330nm, which can absorb signal light in the wavelength range of 1310nm±10nm. Thus, when two types of signal light in the wavelength ranges of 1270nm±10nm and 1310nm±10nm are simultaneously incident on the chip, the signal light in the wavelength range of 1270nm±10nm is first absorbed by the upper light receiving unit 100, while the signal light in the wavelength range of 1310nm±10nm is then absorbed by the lower light receiving unit 100.
[0095] In addition, a distributed Bragg reflection structure 300 is provided on the shared N-type contact layer 12 to increase the reflection of signal light with a wavelength of 1270nm and at the same time improve the transmission of signal light with a wavelength of 1310nm, thereby increasing the absorption efficiency of the light receiving unit 100 for the corresponding wavelength.
[0096] For the materials of other layers of the avalanche photodetector chip in Embodiment 2, the material of the P-type contact layer 11 can be P-type InP, the material of the N-type contact layer 12 can be N-type InP, the electrical isolation material can be a semi-insulating InP(Fe) material, the material of the multiplication layer 15 can be an i-type material based on InAlAs, the material of the charge layer 14 of the upper light receiving unit 100 can be a lightly doped P-type InAlAs or InP material, and the material of the charge layer 14 of the lower light receiving unit 100 can be a lightly doped N-type InAlAs or InP material.
[0097] In summary, the avalanche photodetector chip provided in this embodiment integrates multiple absorption regions on a single chip, forming a single-chip coaxial multi-receiver structure. This enables the avalanche photodetector chip to absorb wavelengths over a wide range without crosstalk. It achieves coaxial operation of optical paths from multiple receiver chips, which simplifies the chip's TO packaging structure.
[0098] When fabricating avalanche photodetector chips, the known avalanche photodetector chip fabrication process can be used. The difference is that one or more light receiving units 100 (i.e., active regions) are grown on the chip epitaxial layer, and optional DBR structures are grown. Since the mature process is used, this not only ensures that the cost will not increase significantly, but also that the reliability risk is relatively low.
[0099] On the other hand, this disclosure also provides an optical receiving module, which includes: a TO package housing and an avalanche photodetector chip located inside the TO package housing, wherein the avalanche photodetector chip is as described in any of the above embodiments of this disclosure.
[0100] The optical receiving module provided in this disclosure has all the advantages of the aforementioned avalanche photodetector chip, which will not be repeated here. The optical receiving module provided in this disclosure can be packaged using a single-fiber, multi-directional, single optical component, eliminating the need for complex wavelength division structures, filters, and other optical path control components, simplifying the packaging process and reducing packaging costs.
[0101] The optical receiving module provided in this disclosure can be applied to multi-generational optoelectronic devices in the PON field, as well as devices with photoelectric conversion requirements such as acquisition devices and communication devices. Taking an acquisition device as an example, the acquisition device may include an optical receiving module and a processor. The optical receiving module converts the acquired optical signal into an electrical signal, and the processor processes the electrical signal; for example, the processor can compress the electrical signal or upload it to a network. Taking a communication device as an example, the communication device may be an optical receiver, a reconfigurable optical add-drop multiplexer, etc. The communication device includes an optical receiving module and a processor. The optical receiving module converts the communication optical signal into an electrical signal, and the processor processes the electrical signal, such as amplifying, shaping, and reducing noise.
[0102] The above description is only for the purpose of enabling those skilled in the art to understand the technical solutions disclosed herein, and is not intended to limit the scope of this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.
Claims
1. An avalanche photodetector chip, characterized in that, The avalanche photodetector chip includes: a multilayer light receiving unit (100) arranged sequentially along the light transmission direction, each of the light receiving units (100) including a P-type contact layer (11), an N-type contact layer (12), and an absorption layer (13), a charge layer (14), and a multiplication layer (15) stacked between the P-type contact layer (11) and the N-type contact layer (12); Along the light transmission direction, the absorption wavelength of the multiple absorption layers (13) of the multilayer light receiving unit (100) gradually increases.
2. The avalanche photodetector chip according to claim 1, characterized in that, At least some of the two adjacent optical receiving units (100) in the multilayer optical receiving unit (100) have an electrical isolation layer (200) to provide electrical isolation between the two adjacent optical receiving units (100).
3. The avalanche photodetector chip according to claim 2, characterized in that, The multilayer optical receiving unit (100) has an electrical isolation layer (200) between any two adjacent optical receiving units (100), so that each multilayer optical receiving unit (100) is independent.
4. The avalanche photodetector chip according to claim 1, characterized in that, At least some of the two adjacent optical receiving units (100) in the multilayer optical receiving unit (100) share the P-type contact layer (11) or the N-type contact layer (12).
5. The avalanche photodetector chip according to any one of claims 1-4, characterized in that, At least two adjacent optical receiving units (100) in the multilayer optical receiving unit (100) have a distributed Bragg reflection structure (300) for reflecting light with wavelengths less than the wavelength threshold range and transmitting light with wavelengths greater than the wavelength threshold range.
6. The avalanche photodetector chip according to claim 5, characterized in that, The avalanche photodetector chip includes an electrical isolation layer (200) for isolating two adjacent optical receiving units (100), and the distributed Bragg reflection structure (300) is disposed on the electrical isolation layer (200).
7. The avalanche photodetector chip according to claim 5, characterized in that, At least some of the two adjacent optical receiving units (100) in the multilayer optical receiving unit (100) share the P-type contact layer (11) or the N-type contact layer (12), and the shared P-type contact layer (11) or the N-type contact layer (12) is provided with the distributed Bragg reflection structure (300).
8. The avalanche photodetector chip according to claim 1, characterized in that, The avalanche photodetector chip also includes an anti-reflection layer (400), which is disposed on the light-incident side of the multilayer light receiving unit (100).
9. The avalanche photodetector chip according to any one of claims 1-8, characterized in that, The optical receiving unit (100) is configured to be arranged in two, three, or four layers.
10. An optical receiving module, characterized in that, The optical receiving module includes: a TO package housing and an avalanche photodetector chip located inside the TO package housing, wherein the avalanche photodetector chip is as described in any one of claims 1-9.