Photoelectric detector using array grating technology
By using array grating technology and periodic stacking arrangement of materials with different refractive indexes in waveguide coupled photodetectors, the mutual constraints between responsiveness and bandwidth are solved, and the responsiveness and light capture capability of the photodetector are improved. More efficient optical signal processing is achieved.
Patent Information
- Application Number
- CN202411198884.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-29
- Publication Date
- 2024-12-20
AI Technical Summary
Waveguide coupled photodetectors have difficulties in optimizing responsiveness, especially inability to withstand high voltages and incident light does not directly enter the absorbing layer, resulting in mutual constraints between responsiveness and bandwidth. It is difficult for the prior art to use such detectors. Improve responsiveness.
Using array grating technology, the diluted waveguide and photodetector active region is grown on the semi-insulating substrate, and the array grating structure is etched on the diluted waveguide side, so that the signal light is first coupled from the end surface into the array grating, and then gradually coupled to the The absorbing layer of the photodetector uses the periodic stacking arrangement of two different refractive index materials and the optical matching layer to improve the coupling efficiency of light.
It effectively improves the responsiveness of the photodetector, reduces the leakage of light, and improves the capture ability of the photodetector and the absorption rate of signal light without changing the coupling method.
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Figure CN119170675A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of optoelectronic technology, and in particular relates to a photoelectric detector using array grating technology. Background Art
[0002] In the field of optoelectronics, photodetectors have many uses, including communication link design, high-speed optical communication systems, space communication systems, and other fields. The main technical indicators of photodetectors include responsivity, 3dB bandwidth, dark current, RF output power, and many others. Among them, responsivity is a physical quantity that judges the photoelectric conversion capability of photodetectors. Photodetectors with higher responsivity can effectively utilize light energy. The greater the responsivity, the higher the sensitivity of the photodetector to changes in light signals.
[0003] There are three main methods to improve the responsivity of photodetectors. The first method is to add a multiplication layer to the photodetector and use the photoelectric effect to make the output signal have a higher gain, thereby improving the responsivity. The typical representative of this type of detector is the avalanche photodetector, whose responsivity can usually be greater than 1A / W. However, this type of technology will amplify the noise while amplifying the signal, making the signal-to-noise ratio of the output signal low. The second method is to thicken the absorption layer of the photodetector so that more light is absorbed by the absorption layer, thereby improving the responsivity. The typical representative of this type of detector is the PIN photodetector, which uses a thicker I layer to significantly improve the responsivity compared to the PN photodiode, usually around 0.3A / W. However, the thicker absorption layer in this solution will significantly affect the electron migration speed, resulting in a reduction in bandwidth. The third method is coating treatment. By coating the light entrance of the photodetector with an anti-reflection film, the coupling loss can be significantly reduced, thereby improving the responsivity. This solution has strict requirements on the selection of coating materials. If lattice-mismatched materials are used for coating, the dark current will increase significantly.
[0004] The incident direction of light in the waveguide-coupled photodetector is perpendicular to the carrier transport direction, which can break the mutual restriction between responsivity and bandwidth and has attracted much attention. In terms of responsivity optimization, due to the size of the device and the limitation of heat dissipation, the waveguide-coupled photodetector cannot withstand higher voltages, and the incident light does not directly enter the absorption layer. Therefore, the first and second methods mentioned above cannot be used on waveguide-coupled photodetectors, and it is very difficult to perform coating treatment on the vertical end surface. Therefore, providing a method for improving the responsivity of waveguide-coupled photodetectors with excellent comprehensive performance is a problem worth studying for those skilled in the art. Summary of the invention
[0005] The object of the present invention is to provide a photoelectric detector using array grating technology to solve the problems existing in the above-mentioned prior art.
[0006] To achieve the above object, the technical solution of the present invention is: a photoelectric detector using array grating technology, characterized in that
[0007] A photodetector using array grating technology, in which a dilution waveguide and a photodetector active region are grown on a semi-insulating substrate, and an array grating structure is grown after a certain length of the dilution waveguide is etched off on the waveguide side, so that the signal light is first coupled into the array grating from the end face for initial convergence, then terminated into the dilution waveguide, and gradually coupled upward to the photodetector absorption layer in the dilution waveguide, and finally absorbed and converted into photogenerated carriers in the photodetector absorption layer. This structure can enhance the photodetector's ability to capture optical power, couple more light into the absorption layer, and help improve the photodetector's responsiveness.
[0008] Furthermore, the array grating is composed of two materials with different refractive indices stacked and arranged periodically, both materials can match the substrate lattice, and the thickness distribution of different materials in a single period is changed accordingly according to the different working wavelengths. This structure can converge the incident light and effectively reduce the leakage of light.
[0009] Furthermore, the dilution waveguide uses two materials for alternating epitaxy, one of which is the same as the material of the semi-insulating substrate, and the thickness of the material decreases layer by layer from bottom to top; the other material is a material with a refractive index greater than the aforementioned material and meets lattice matching conditions; this structure allows the incident light to be coupled upward into the epitaxial layer of the photodetector.
[0010] Furthermore, there is an optical matching layer between the dilution waveguide and the photodetector active area. The refractive index of the optical matching layer material is between that of the bottom epitaxial layer of the photodetector active area and the top dilution waveguide layer, and meets the lattice matching requirements, thereby improving the efficiency of upward coupling of incident light.
[0011] Furthermore, the epitaxial layer components of the active region of the photodetector from bottom to top are composed of an N contact layer, a sub-collection layer, a collection layer, a buffer layer, an absorption layer, an electron blocking layer, and a P contact layer. Light absorption occurs in the absorption layer, and the refractive index of the epitaxial layer structure of the photodetector gradually increases from bottom to top until the refractive index of the electron blocking layer is less than that of the absorption layer.
[0012] Preferably, the structure and thickness of each layer of the array grating and the dilution waveguide can be adjusted according to actual light coupling requirements, and the design of each epitaxial layer of the photodetector needs to be adjusted accordingly to improve device performance.
[0014] Compared with the prior art, the present invention has the following beneficial effects:
[0015] One of the innovations of this solution is that the present invention provides a photodetector using array grating technology. In this device, a dilution waveguide and a photodetector active region are first epitaxially grown on a semi-insulating substrate in sequence, and then a dilution waveguide of a certain length is etched and then an array grating structure is grown on the semi-insulating substrate, so that the signal light is first coupled from the end face into the array grating for initial convergence, and then terminated into the dilution waveguide, and gradually coupled upward to the photodetector absorption layer in the dilution waveguide. Compared with existing photodetectors, the photodetector using array grating technology in this solution can capture more optical power and couple it into the absorption layer, effectively improving the responsivity of the photodetector.
[0016] An innovative point of the present solution is that the present invention provides a photoelectric detector using array grating technology, in which the incident signal light first passes through the array grating, and the array grating has the function of an equivalent lens and can converge the signal light.
[0017] An innovative point of the present solution is that the present invention provides a photoelectric detector using array grating technology, in which incident signal light is coupled through cascade light of the array grating and the dilution waveguide, so that light leakage is improved.
[0018] An innovative point of the present solution is that the present invention provides a photodetector using array grating technology, which can reduce the leakage of signal light outside the active area of the photodetector without changing the coupling mode of the waveguide photodetector, thereby improving the responsiveness of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on the provided drawings without creative work.
[0020] Figure 1 It is a structural schematic diagram of a specific implementation mode of the present invention.
[0021] Figure 2 It is a schematic cross-sectional view of the photodetector used in the present invention in a direction parallel to the incident light.
[0022] Figure 3 It is a schematic cross-sectional view of the array grating used in the present invention.
[0023] Figure 4 It is a structural schematic diagram of a specific embodiment of the specific implementation method of the present invention.
[0024] Figure 5It is a distribution diagram of the incident light field when the photoelectric detector according to a specific embodiment of the present invention is working. DETAILED DESCRIPTION
[0025] Below in conjunction with the appended Figures 1 to 5 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0026] Example:
[0027] Figure 1 This is a structural diagram of a photodetector using array grating technology of the present invention, comprising a semi-insulating substrate 10, an array grating 11, a dilution waveguide 9 and a photodetector active region (including epitaxial layers 1-8); the array grating 11, the dilution waveguide 9 and the photodetector active region are all integrated on the semi-insulating substrate 10; wherein the array grating 11 is terminated with the dilution waveguide 9; the bottom layer of the epitaxial layer structure of the photodetector active region contains an optical matching layer, which is layered with the dilution waveguide layer through the optical matching layer; the photodetector active region area is smaller than the dilution waveguide area. The signal light is incident at the front end of the array grating, passes through the array grating and the dilution waveguide in turn, is gradually coupled upward into the photodetector active region in the dilution waveguide layer, is absorbed in the absorption layer of the photodetector active region, and is converted into an electrical signal and output from the electrode.
[0028] Furthermore, the array grating can converge the incident signal light first, effectively reducing the phenomenon of signal light leaking out of the active area of the photodetector.
[0029] Furthermore, the dilution waveguide can achieve the goal of gradually coupling the signal light upwards into the absorption layer of the active region of the photodetector by appropriately adjusting the periodically distributed material and the thickness of each layer.
[0030] Furthermore, the active region of the photodetector can absorb light coupled into the absorption layer from the dilution waveguide 9 below, and convert it into an electrical signal to be output from the electrode.
[0031] Figure 2The figure is a schematic diagram of the positions of the epitaxial layers, array grating 11, and dilution waveguide 9 of the active region of the photodetector used in the example in the direction parallel to the incident light. The epitaxial layer part from bottom to top includes N contact layer 7, sub-collection layer 6, collection layer 5, buffer layer 4, absorption layer 3, electron blocking layer 2, and P contact layer 1, which constitute the active region of the photodetector. N electrode 13 and P electrode 12 are also provided on the N contact layer and the P contact layer, respectively. The active region of the photodetector is connected to the dilution waveguide layer 9 through the optical matching layer 8. The array grating 11 is located at the front end of the dilution waveguide 9, and the bottom layer is the semi-insulating substrate 10.
[0032] Figure 3 It is the structure of each epitaxial layer of the array grating used in the example. The epitaxial structure of the array grating periodic unit 14 is to grow a layer of array grating material B between two layers of array grating material A to form an ABA type structural unit; the thickness of the array grating periodic unit is kept fixed, and the thickness of the array grating material B is adjusted to the optimal coupling efficiency according to the wavelength of the incident light; there is a refractive index difference between the array grating material A and the array grating material B, and both are lattice matched with the semi-insulating substrate 10.
[0033] Figure 4 1 is a schematic diagram of a specific embodiment of a photoelectric detector using array grating technology provided by the present invention. Figure 2 The structures shown are consistent.
[0034] The material used for the semi-insulating substrate 10 is lattice-matched with the material used for the dilution waveguide 9 and the array grating 11, and has a lower refractive index to prevent light from leaking from this layer.
[0035] The array grating 11 is composed of two materials with different refractive indices that are periodically stacked and arranged. One material is selected to be the same material as the substrate, and the other material has a refractive index difference of 0.25 with the substrate material and can match the substrate lattice. The overlapping layers of the two materials are designed to have a total of 10 periods, and the overall thickness is 1.75mm; the entire array grating length is 1mm.
[0036] The diluted waveguide layer 9 is made of two materials for alternating epitaxy, one of which is the same material as the substrate, and the other is a material that matches the substrate lattice and has a larger refractive index. The two materials overlap each other in the vertical direction, with a total of 5 cycles designed, and the overall thickness is 1.75 mm; the entire diluted waveguide length is 42 mm.
[0037] The optical matching layer 8 is located on the diluted waveguide layer 9. The refractive index of the material used for the optical matching layer is between the N-contact layer 7 and the uppermost layer of the diluted waveguide layer 9, and is used to increase the optical coupling efficiency between the diluted waveguide layer 9 and the active region of the photodetector.
[0038] The N-contact layer 7 is located on the optical matching layer 8. The refractive index of the material used in the N-contact layer is higher than that of the optical matching layer 8, and heavy donor doping is used to form an ohmic contact. A metal electrode N-electrode 13 is located on the N-contact layer 7.
[0039] The sub-collection layer 6 is located above the N-contact layer 7. The refractive index of the material used in this layer is higher than that of the N-contact layer 7 material, and heavy donor type doping is used. Its function is to prevent the heavy donor type dopant of the N-contact layer from diffusing into the collection layer, while ensuring that electrons are buffered when passing through the collection layer at high speed.
[0040] The collection layer 5 is located on the sub-collection layer 6. The refractive index of the material used in this layer is higher than that of the N-contact layer material, and donor-type doping is used to collect carriers generated by light absorption.
[0041] The buffer layer 4 is located on the collection layer 5 and uses heavy donor doping to smooth the energy band and accelerate photogenerated carriers.
[0042] The absorption layer 3 is located on the buffer layer 4. The material used in this layer is a material that can absorb photons and has a higher refractive index than the layers below. In this layer, signal light is absorbed and photogenerated carriers are generated. The doping of this layer adopts acceptor-type Gaussian doping.
[0043] The electron blocking layer 2 is located above the absorption layer 3. The material used in this layer has a lower refractive index than the material of the absorption layer 3. It serves as the cladding of the absorption layer 3 to limit the signal light from continuing to propagate upward. The doping type used in this layer is heavy acceptor type doping, which is used to block the reverse propagation of electrons.
[0044] The P contact layer 1 is on the electron blocking layer 2. The material used for this layer is the same as that of the absorption layer 3 and is heavily doped with acceptor type so as to form an ohmic contact with the P electrode 12. On the P contact layer 1 is the metal electrode P electrode 12.
[0045] Figure 5 It is the incident light field distribution diagram of the photodetector according to a specific embodiment of the present invention. In this example, the peak power of the light field transmitted to the absorption layer after the signal light is incident is 20% of the incident light power, the overall absorption rate is 0.71, and the calculated responsivity is 0.9A / W. In comparison, when the array grating is not added, the responsivity of the active area of the same photodetector is 0.8A / W.
[0046] The principle of the present invention is as follows: the signal light is first coupled into the array grating from the end face, and diffraction occurs inside the array grating, causing the light's forward direction to change and converge. The signal light in the array grating is initially converged, and then enters the dilution waveguide, where it is gradually coupled upward into the photodetector active area, and finally guided by the refractive index in each epitaxial layer of the photodetector active area, and coupled into the absorption layer. Due to the low refractive index limitation of the electron blocking layer material, the signal light is confined in the absorption layer, and is converted into photogenerated carriers after being absorbed, wherein the holes relax rapidly in the absorption layer due to the high acceptor-type doping, and the electrons are exported from the N electrode after passing through each epitaxial layer of the photodetector active area downward.
[0047] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range consistent with the principles and novel features disclosed herein.
Claims
1. A photoelectric detector using array grating technology, characterized in that: The device consists of functional units such as semi-insulating substrate, array grating, dilution waveguide, photodetector active area and electrodes.
2. A photoelectric detector using array grating technology as claimed in claim 1, characterized in that: The dilution waveguide and the photodetector active region are epitaxially grown based on the semi-insulating substrate, and the array grating is epitaxially grown after a certain length of the dilution waveguide is etched off on the waveguide side, so that the signal light is first coupled into the array grating from the end face for initial convergence, and then terminated into the dilution waveguide, and gradually coupled upward in the dilution waveguide to the absorption layer in the active region of the photodetector.
3. A photoelectric detector using array grating technology as claimed in claim 1, characterized in that: The array grating is terminated with the dilution waveguide and both are directly laminated with the semi-insulating substrate.
4. A photoelectric detector using array grating technology as claimed in claim 1, characterized in that: When the photodetector is working, the signal light is first coupled from the end face into the array grating for preliminary convergence, then terminated into the dilution waveguide, gradually coupled upward to the photodetector absorption layer in the dilution waveguide, and finally absorbed and converted into photogenerated carriers in the photodetector absorption layer. This structure can enhance the ability of the photodetector to capture optical power, couple more light into the absorption layer of the detector, and help improve the responsiveness of the photodetector.
5. A photoelectric detector using array grating technology as claimed in claim 1, characterized in that: The array grating is composed of two materials with different refractive indices that are periodically stacked and arranged. The epitaxial structure of the array grating periodic unit is to grow a layer of array grating material B between two layers of array grating material A to form an ABA type structural unit. The thickness of the array grating periodic unit is fixed. There is a certain refractive index difference between the two materials, and both can match the substrate lattice. The thickness distribution of the two materials within the unit period can be optimized accordingly according to the change of the working wavelength.
6. A photoelectric detector using array grating technology as claimed in claim 1, characterized in that: The dilution waveguide uses two materials for alternating epitaxy, one of which is the same as the material of the semi-insulating substrate and the thickness of the material decreases layer by layer from bottom to top, and the other material has a refractive index greater than the aforementioned material and meets the lattice matching condition.
7. A photoelectric detector using array grating technology as claimed in claim 1, characterized in that: The sizes of the array grating and the dilution waveguide can be adjusted according to the actual requirements of coupled light, and the size of the active area of the photodetector needs to be adjusted accordingly to improve the performance of the device.