Single-pixel detector micro-spectrometer with a graded bandgap absorption layer structure

Abstract

The present application relates to a kind of single-pixel detector microspectrometer with gradually changing band gap absorption layer structure, including substrate layer, cathode contact layer, gradually changing band gap absorption layer, barrier layer, absorption layer and anode contact layer from bottom to top, two metal electrodes of cathode and anode are respectively generated on cathode contact layer and anode contact layer.Coding specificity is carried out to incident spectral information by gradually expanding spectral absorption range with gradually changing band gap semiconductor material as absorption layer, and incident spectrum is reconstructed efficiently and quickly by cooperating with reconstruction algorithm;The material system prepared by adopting bulk material as detector is mature in related process, and compared with new materials such as two-dimensional material, its preparation is more simple, and cost is lower;The bulk part only has a single-pixel photodetector, and can work without complicated optical elements and optical path, so that extremely small size can be realized, size can be changed arbitrarily with photoetching plate, and different application scenarios under different demands are met.

Description

Technical Field

[0001] This invention relates to a photoelectric detection technology, and more particularly to a micro spectrometer with a single-pixel detector having a gradient bandgap absorption layer structure. Background Technology

[0002] Spectrometers have wide applications in industrial production, chemical composition analysis, and environmental monitoring. With the development of artificial intelligence-related technologies such as autonomous driving and machine vision, applications like spectral analysis and hyperspectral imaging have created new demands for the miniaturization of spectrometers. Traditional approaches to implementing miniature spectrometers, both domestically and internationally, include dispersive optics, narrowband filters, and Fourier transform. However, due to the limitations of the size of the dispersive elements and optical paths, these three approaches struggle to reduce the overall spectrometer system size to the sub-millimeter scale while maintaining high resolution. Computational reconstruction methods can free miniature spectrometer systems from the limitations of dispersive elements and optical paths; therefore, computational reconstruction is currently considered the most promising and valuable approach for miniature spectrometer implementation, both domestically and internationally.

[0003] However, current computational reconstruction schemes for ultracompact spectrometers still suffer from limitations such as insufficient size, complex and reproducible material growth processes, and difficulties in large-scale mass production and application. Further research is needed to achieve miniature spectrometers that are small in size, have simple manufacturing processes, and are inexpensive and readily mass-producible. Summary of the Invention

[0004] To address the issues of insufficient size and difficulty in large-scale fabrication of existing ultracompact spectrometers, a micro-spectrometer with a single-pixel detector featuring a gradient bandgap absorption layer structure is proposed. This detector boasts advantages such as high responsivity, low dark current, and high detectivity, and its fabrication process is simple, mature, and suitable for mass production.

[0005] The technical solution of the present invention is: a single-pixel detector micro spectrometer with a gradient bandgap absorption layer structure, which includes, from bottom to top, a substrate layer, a cathode contact layer, a weak N-type gradient bandgap absorption layer, a blocking layer, an absorption layer and an anode contact layer, with two metal electrodes, a cathode and an anode, respectively formed on the cathode contact layer and the anode contact layer.

[0006] The graded bandgap absorption layer and the absorption layer are used to absorb photons incident from the surface of the single-pixel detector to excite electron-hole pairs within the two layers. The graded bandgap absorption layer is a weakly N-type doped absorption layer material with multiple lattice-matched bandgap layers that continuously narrow downwards. The graded bandgap absorption layer absorbs light of different wavelengths and collects corresponding photogenerated carriers. Under different operating voltages, the absorption layers with different bandgaps contribute photogenerated carriers, and the spectral response has different cutoff wavelengths. The spectral information is encoded into the voltage and current characteristics of the single-pixel detector, and the voltage and current characteristics are used to reconstruct the spectral information.

[0007] The barrier layer is used to prevent the generated holes from spreading towards the anode.

[0008] Preferably, the substrate is a GaAs substrate, and the graded bandgap absorption layer on the GaAs substrate is an Al. x Ga (1-x) Materials transitioning from As to GaAs have x decreasing from large to small, and the doping concentration is weak N-type doping.

[0009] Preferably, the gradient bandgap absorbing layer is an AlGaAs / GaAs gradient bandgap absorbing layer, in which the AlGaAs layer gradually transitions to the GaAs layer, with a total thickness of about 2100 nm and a weak N-type doping concentration; the AlGaAs absorbing layer has a thickness of 200 nm and a weak N-type doping concentration.

[0010] Preferably, the substrate layer is an InP substrate layer, and the graded bandgap absorption layer on the InP substrate layer is an InP substrate layer. x Ga (1-x) As y P (1-y) Gradient to In 0.53 Ga 0.47 As material, y increases from small to large, x is adjusted accordingly to maintain lattice matching with the InP substrate, and the doping concentration is weak N-type doping; or, on the InP substrate layer, the gradient bandgap absorption layer is In x Al y Ga (1-x-y) As gradually changes to In 0.53 Ga 0.47 As material, y decreases from large to small, with a maximum value of 0.52. x is adjusted accordingly to maintain lattice matching with the InP substrate, and the doping concentration is weak N-type doping.

[0011] Preferably, the substrate layer is a GaAs substrate layer, the cathode contact layer is an N-type heavily doped cathode contact layer, the anode contact layer is a P-type heavily doped anode contact layer, the barrier layer is an N-type lightly doped wide-bandgap hole barrier layer, and the absorber layer 14 is an N-type lightly doped absorber layer.

[0012] Preferably, the cathode contact layer is a GaAs cathode contact layer with a doping concentration of 1×10⁻⁶. 18 cm -3 The anode contact layer is a GaAs anode contact layer with a doping concentration of 1×10⁻⁶. 18 cm -3 The barrier layer is an InGaP barrier layer with a doping concentration of 3 × 10⁻⁶. 15 cm -3 The absorption layer is Al. 0.5 Ga 0.5As absorption layer, with a doping concentration of 3×10⁻⁶. 15 cm -3 .

[0013] The beneficial effects of this invention are as follows: This invention features a single-pixel detector micro-spectrometer with a gradient bandgap absorption layer structure. It uses a semiconductor material with a gradient bandgap as the absorption layer, which can gradually expand the spectral absorption range with increasing bias voltage, thereby specifically encoding the incident spectral information. Combined with a reconstruction algorithm, the incident spectrum can be reconstructed efficiently and rapidly. It uses a bulk material as the material system for detector fabrication, and the related processes are mature and simpler and less expensive than new materials such as two-dimensional materials. Its physical part consists of only a single photodetector, eliminating the need for complex beam-splitting elements and optical paths, allowing for extremely small dimensions that can be arbitrarily varied with the photolithography plate to meet different application scenarios. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of step one in the fabrication method of the single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure of the present invention.

[0015] Figure 2 This is a schematic diagram of step two in the fabrication method of the single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure of the present invention;

[0016] Figure 3 This is a schematic diagram of step three in the fabrication method of the single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure of the present invention;

[0017] Figure 4 This is a schematic diagram of step four in the fabrication method of the single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure of the present invention;

[0018] Figure 5 This is a schematic diagram of the three-dimensional structure of the single-pixel detector micro spectrometer with a gradient bandgap absorption layer structure according to the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0020] like Figure 1The diagram shows a single-pixel detector micro-spectrometer with a gradient bandgap absorption layer structure. The single-pixel detector micro-spectrometer includes, from bottom to top, a substrate layer 10, a cathode contact layer 11, a gradient bandgap absorption layer 12, a blocking layer 13, an absorption layer 14, and an anode contact layer 15. The cathode and anode metal electrodes are respectively generated on the cathode contact layer 11 and the anode contact layer 15. The gradient bandgap absorption layer 12 and the absorption layer 14 are used to absorb photons to excite electron-hole pairs within the two layers. The blocking layer 13 is used to block the generated holes from diffusing towards the anode.

[0021] This embodiment of the single-pixel detector micro-spectrometer employs a hole-blocking layer to suppress hole drift towards the anode under low bias. By designing a graded bandgap absorption layer structure, the optical response under different bias voltages is specifically altered. When the difference between the electron conduction band energy level and the hole valence band energy level of the depleted absorption layer material is less than the energy corresponding to a photon of a specified wavelength, a portion of the material in the graded bandgap absorption layer can absorb light of that wavelength and collect the corresponding photogenerated carriers, thereby achieving a response cutoff wavelength dependent on the bias voltage. Therefore, the cutoff wavelength of the photodetector of this invention continuously extends with increasing reverse bias voltage, encoding spectral information into the voltage and current characteristics of the device for further calculation and reconstruction to obtain spectral information, thus realizing the spectrometer function.

[0022] The gradient bandgap absorption layer 12 is a weakly N-type doped absorption layer material with multiple lattice matching, where the composition decreases downwards and the bandgap narrows downwards.

[0023] The substrate layer includes a GaAs substrate layer, an InP substrate layer, etc., and on the GaAs substrate, the graded bandgap absorption layer is Al. x Ga (1-x) The material transitions from As to GaAs, with x decreasing from large to small, and the doping concentration is weakly N-type doped; on an InP substrate, the gradient bandgap absorption layer can be In... x Ga (1-x) As y P (1-y) Gradient to In 0.53 Ga 0.47 As material, y increases from small to large, and x is adjusted accordingly to maintain lattice matching with the InP substrate; the doping concentration is weak N-type doping; on the InP substrate, the gradient bandgap absorption layer can also be In x Al y Ga (1-x-y) As gradually changes to In 0.53 Ga 0.47 As material, y decreases from large to small, with a maximum value of 0.52. x is adjusted accordingly to maintain lattice matching with the InP substrate, and the doping concentration is weak N-type doping.

[0024] Taking a GaAs substrate as an example, in the AlGaAs / GaAs graded bandgap absorber layer 12, the AlGaAs layer gradually transitions to the GaAs layer, with a total thickness of approximately 2100 nm and a weak N-type doping concentration; the AlGaAs absorber layer has a thickness of approximately 200 nm and a weak N-type doping concentration. Preferably, the doping concentration of the AlGaAs / GaAs graded bandgap absorber layer 12 is 3 × 10⁻⁶. 15 cm -3 about.

[0025] As an example, the substrate layer 10 is a GaAs substrate layer, the cathode contact layer 11 is an N-type heavily doped cathode contact layer, the anode contact layer 15 is a P-type heavily doped anode contact layer, the barrier layer 13 is an N-type lightly doped wide-bandgap hole barrier layer, and the absorber layer 14 is an N-type lightly doped absorber layer.

[0026] The substrate layer is a lattice-matched GaAs substrate layer, which can effectively reduce problems such as dark current caused by interface defects and dislocations, and improve the detection accuracy of the detector.

[0027] The cathode contact layer 11 is a GaAs cathode contact layer with a doping concentration of 1×10⁻⁶. 18 cm -3 The anode contact layer 15 is a GaAs anode contact layer with a doping concentration of 1×10⁻⁶. 18 cm -3 Left and right; the barrier layer 13 is an InGaP barrier layer with a doping concentration of 3×10⁻⁶. 15 cm -3 Left and right; the absorption layer 14 is Al 0.5 Ga 0.5 As absorption layer, with a doping concentration of 3×10⁻⁶. 15 cm -3 about.

[0028] The specific steps in fabricating the single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure include:

[0029] like Figure 1 Step 1 shown: Using molecular beam epitaxy, a cathode contact layer 11, a graded bandgap absorption layer 12, a barrier layer 13, an absorption layer 14, and an anode contact layer 15 are sequentially grown on the substrate layer 10.

[0030] In this embodiment, the materials, thicknesses, and doping concentrations of each of the above layers are shown in Table 1:

[0031] Table 1

[0032] Material thickness Doping type Doping concentration GaAs anode contact layer 30nm P+ <![CDATA[1×10 18 cm -3 ]]> <![CDATA[Al 0.5 Ga 0.5 As absorption layer]]> 200nm N- <![CDATA[3×10 15 cm -3 ]]> InGaP barrier layer 30nm N- <![CDATA[3×10 15 cm -3 ]]> <![CDATA[Al 0.5 Ga 0.5 As / GaAs graded bandgap absorption layer 2100nm N- <![CDATA[3×10 15 cm -3 ]]> GaAs cathode contact layer 200nm N+ <![CDATA[1×10 18 cm -3 ]]> GaAs substrate 500μm

[0033] The cathode contact layer consists of a 200 nm thick layer with a doping concentration of 1 × 10⁻⁶. 18 cm -3 It is composed of n-type GaAs.

[0034] The structure of the AlGaAs / GaAs graded bandgap absorption layer is as follows: Al 0.5 Ga 0.5 The As layer gradually transitions to the GaAs layer, with the Al content gradually decreasing and the corresponding band gap gradually shrinking. The total thickness is 2100 nm, the doping type is N-type, and the doping concentration is 3 × 10⁻⁶. 15 cm -3 .

[0035] The InGaP electron blocking layer is 30 nm thick, N-doped, and has a doping concentration of 3 × 10⁻⁶. 15 cm -3 .

[0036] The Al 0.5 Ga 0.5 The As absorber layer is 200 nm thick, N-type doped, and has a doping concentration of 3 × 10⁻⁶. 15 cm -3 .

[0037] The GaAs anode contact layer has a thickness of 30 nm, is p+ type doped, and has a doping concentration of 1 × 10⁻⁶. 18 cm -3 .

[0038] like Figure 2 Step 2: Titanium, platinum, and gold are deposited on the upper surface of the anode contact layer 15 using electron beam evaporation technology to form the anode 16. In this embodiment, the thicknesses of titanium, platinum, and gold in the anode 16 are selected to be 20 nm, 20 nm, and 300 nm, respectively.

[0039] like Figure 3 Step 3: Using wet etching, etch sequentially from the anode 16 downwards until the etched surface stops within the cathode contact layer 11, forming a cylindrical step 17 protruding from the cathode contact layer 11.

[0040] As an example, after forming the cylindrical step 17, the outer wall of the cylindrical step 17 also needs to be passivated. The insulating material used for the passivation treatment is SiO2 or SiN. x , forming as Figure 5 The 19th passivation layer is shown.

[0041] like Figure 4Step four is shown: Titanium, platinum, and gold are sequentially deposited on the surface of the cathode contact layer 11 using electron beam evaporation technology to form the cathode 18. In this embodiment, the thicknesses of titanium, platinum, and gold in the cathode 18 are selected to be 20 nm, 20 nm, and 300 nm, respectively.

[0042] like Figure 5 The three-dimensional structure diagram after fabrication is shown. Experiments show that the single-detector micro spectrometer fabricated through the above steps has a resolvable wavelength range (incident light 20) of 480 nm to 840 nm at room temperature, a responsivity of 0.46 A / W at 575 nm, and a quantum efficiency of 74% at 575 nm. It realizes the function of changing the spectral response cutoff wavelength with the bias voltage, and can efficiently and quickly reconstruct the incident spectrum based on the reconstruction algorithm. Furthermore, this example has realized a single-pixel detector micro spectrometer with a minimum size of about 50 micrometers in diameter.

[0043] The material system on which this invention is based has a mature technical route and production system for growth and preparation, with low preparation cost, stable performance, and high reproducibility of preparation route.

[0044] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A miniature spectrometer with a single-pixel detector and a graded bandgap absorption layer structure, characterized in that, The physical device comprises only a single photodetector, consisting of, from bottom to top, a substrate layer, a cathode contact layer, a weak N-type graded bandgap absorption layer, a blocking layer, an absorption layer, and an anode contact layer. Two metal electrodes, the cathode and anode, are formed on the cathode and anode contact layers, respectively. The graded bandgap absorption layer and the absorption layer absorb photons incident from the surface of the single-pixel detector to excite electron-hole pairs within the two layers. The graded bandgap absorption layer is a weak N-type doped absorption layer material with multiple lattice-matched bandgap layers that continuously narrow downwards. The graded bandgap absorption layer absorbs light of different wavelengths and collects corresponding photogenerated carriers. The doping concentration of the weak N-type doped absorption layer material is 3 × 10⁻⁶. 15 cm -3 Under different operating voltages, the gradient bandgap absorption layer contributes photogenerated carriers, and the spectral response has different cutoff wavelengths, encoding the spectral information into the voltage and current characteristics of the single-pixel detector. The voltage and current characteristics are used to reconstruct the spectral information. The blocking layer is used to block the generated holes from diffusing towards the anode.

2. The single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure according to claim 1, characterized in that, The substrate is a GaAs substrate, and the graded bandgap absorption layer on the GaAs substrate is an Al substrate. x Ga （1-x） Materials transitioning from As to GaAs have x decreasing from large to small, and the doping concentration is weak N-type doping.

3. The single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure according to claim 2, characterized in that, The graded bandgap absorption layer is an AlGaAs / GaAs graded bandgap absorption layer, with the AlGaAs layer gradually transitioning to the GaAs layer. The total thickness is 2100 nm, and the doping concentration is weak N-type doping. The thickness of the AlGaAs layer is 200 nm, and the doping concentration is weak N-type doping.

4. The single-pixel detector miniature spectrometer with a gradient bandgap absorption layer structure according to claim 1, characterized in that, The substrate is an InP substrate, and the graded bandgap absorption layer on the InP substrate is an In... x Ga （1-x） As y P (1-y) Gradient to In 0.53 Ga 0.47 As material, y increases from small to large, x is changed accordingly to maintain lattice matching with InP substrate, and the doping concentration is weak N-type doping; Alternatively, on an InP substrate, the graded bandgap absorption layer is In x Al y Ga （1-x-y） As gradually changes to In 0.53 Ga 0.47 As material, y decreases from large to small, with a maximum value of 0.

52. x is adjusted accordingly to maintain lattice matching with the InP substrate, and the doping concentration is weak N-type doping.

5. The single-pixel detector miniature spectrometer with a graded bandgap absorption layer structure according to any one of claims 1 to 3, characterized in that, The substrate is a GaAs substrate, the cathode contact layer is an N-type heavily doped cathode contact layer, the anode contact layer is a P-type heavily doped anode contact layer, the barrier layer is an N-type lightly doped wide-bandgap hole barrier layer, and the absorber layer is an N-type lightly doped absorber layer.

6. The single-pixel detector miniature spectrometer with a graded bandgap absorption layer structure according to claim 5, characterized in that, The cathode contact layer is a GaAs cathode contact layer with a doping concentration of 1×10⁻⁶. 18 cm -3 The anode contact layer is a GaAs anode contact layer with a doping concentration of 1×10⁻⁶. 18 cm -3 The barrier layer is an InGaP barrier layer with a doping concentration of 3 × 10⁻⁶. 15 cm -3 The absorption layer is Al. 0.5 Ga 0.5 As absorption layer, with a doping concentration of 3×10⁻⁶. 15 cm -3 .

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