A method for gain modulation of a dual-band graphene-based detector

Abstract

The application discloses a gain modulation method of a dual-band detector based on graphene. The modulation method is to add two kinds of incident light with different wavelengths, utilize the different light absorbance of the light absorption layer to different wavelengths of incident light, achieve different optical effects to realize the suppression or promotion of the built-in field of the vertical heterojunction, change the Fermi level of the graphene, and then modulate the original optical signal response. The response of the two signals after modulation can be distinguished obviously. The dual-band detector based on graphene can realize the response to different bands of light at the same time, greatly improve the response, and the modulation method is simple and practical.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, and in particular to a gain modulation method for a graphene-based dual-band detector. Background Technology

[0002] The current low gain of dual-band detection based on low-dimensional materials is mainly due to the low carrier mobility of the materials in the device, which fails to fully utilize the gain advantage of the dual-band detection composite structure of low-dimensional materials. The introduction of high-mobility graphene has the potential to improve the gain of stacked dual-band detection devices.

[0003] Currently, there are two ways to implement dual-band photoelectric detection at the hardware level. One is based on a wideband detector that simultaneously responds to two bands, designing two optical lenses that transmit through the two bands respectively to collect photoelectric information from each band. This method requires high-precision optical design and significantly increases the size of the imaging system in practical applications. The other method is based on a combination of detectors that respond to the two bands separately. Detector 1 responds only to band 1, and detector 2 responds only to band 2, thus requiring only one optical system and greatly simplifying the optical design. Taking the design of a mercury cadmium telluride infrared detector as an example, using a back-illuminated mode, by controlling the thickness of the light-absorbing layer of detector 1, all short-wavelength incident light is absorbed by detector 1, so detector 2 only responds to long wavelengths, thereby distinguishing the response currents of the two bands. The above dual-band operating mode has been applied to infrared detectors such as mercury cadmium telluride. However, like single-band detectors, dual-band detectors based on materials such as mercury cadmium telluride also face problems such as low gain and weak response to weak signals.

[0004] Currently, there is a lack of methods to comprehensively modulate the photocurrent magnitude, operating speed, and signal direction of a photodetector by modulating the optical input. Optical modulation is expected to provide a multifunctional platform to replace electrical modulation and explore more practical optoelectronic devices. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a gain modulation method for a graphene-based dual-band detector, which can effectively change the output current, thereby changing the responsivity and making dual-band signal extraction more effective.

[0006] Therefore, the technical solution of the present invention is:

[0007] A gain modulation method for a graphene-based dual-band photodetector, wherein the graphene-based dual-band photodetector comprises a first light-absorbing layer, a graphene layer, and a second light-absorbing layer, wherein the graphene layer is placed between the first light-absorbing layer and the second light-absorbing layer to form a sandwich structure; and a metal electrode is disposed on the surface of the graphene layer.

[0008] The gain modulation method includes:

[0009] The first signal light is incident on the photodetector and absorbed by the first light absorption layer to form a first graphene / light absorption layer vertical Schottky junction, and the generated photogenerated carriers enter the graphene layer.

[0010] The second signal light is incident on the photodetector and absorbed by the second light absorption layer, forming a vertical Schottky junction of the second graphene / light absorption layer B. The generated photogenerated carriers enter the graphene layer.

[0011] Furthermore, the first light-absorbing layer is made of a short-wavelength absorbing material and does not absorb long waves.

[0012] Furthermore, the second light-absorbing layer is made of a long-wavelength absorbing material and does not absorb short waves.

[0013] Furthermore, the thickness of the first light-absorbing layer is greater than the cutoff wavelength of the incident light absorbed by the material in that layer.

[0014] Furthermore, the first signal light is light with different wavelengths, passing through the first light absorption layer, the graphene layer, and then the second light absorption layer; the long-wavelength portion of the first signal light is absorbed by the second light absorption layer after passing through the first light absorption layer and the graphene layer.

[0015] Furthermore, the first signal light is visible light.

[0016] Furthermore, the second signal light is infrared light.

[0017] Furthermore, the photogenerated carriers generated when the first signal light and the second signal light are incident on the photodetector enter the graphene layer, causing a change in the Fermi level of the graphene layer.

[0018] Furthermore, the Fermi level of the graphene changes, leading to either suppression or promotion of carrier transfer.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The modulation method of this invention involves introducing two incident lights of different wavelengths. By utilizing the different absorbance of the light-absorbing layer for these different wavelengths, different optical effects are achieved to suppress or promote the built-in field of the vertical heterojunction, thereby altering the Fermi level of graphene and modulating the responsivity of the original optical signal. The responsivity of the two signals after modulation can be clearly distinguished. This invention, combined with a graphene-based dual-band detector, not only enables simultaneous response to light of different wavelengths but also significantly improves responsivity. Furthermore, the modulation method is simple and highly practical. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a graphene-based dual-band detector according to an embodiment of the present invention. In the figure, 1 is the first light absorption layer, 2 is the graphene layer, 3 is the second light absorption layer, and 4 is the metal electrode.

[0023] Figure 2 This is a flowchart of a gain modulation method for a graphene-based dual-band detector according to an embodiment of the present invention. Detailed Implementation

[0024] The following examples are merely illustrative of the invention, and the scope of the invention is not limited to the embodiments described. Therefore, any non-essential modifications and adjustments made by those skilled in the art based on the above description to other embodiments are still within the scope of protection of this invention.

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] This invention provides a graphene-based dual-band detector, such as... Figure 1 As shown, the dual-band detector consists of a first light-absorbing layer 1, a graphene layer 2, and a second light-absorbing layer 3 from top to bottom. The graphene layer 2 is placed between the first light-absorbing layer 1 and the second light-absorbing layer 3, forming a sandwich structure. A metal electrode 4 is disposed on the surface of the graphene layer 2. This dual-band detector is a sandwich structure that can realize dual-band and high-gain photoelectric detection.

[0027] In some embodiments, the material of the first light-absorbing layer 1 is a short-wavelength absorbing material that does not absorb long waves; the material of the second light-absorbing layer 3 is a long-wavelength absorbing material that does not absorb short waves; and the graphene layer 2 provides a high-gain carrier transport channel for both the first light-absorbing layer 1 and the second light-absorbing layer.

[0028] In some embodiments, the thickness of the first light-absorbing layer 1 should be greater than the length of the cutoff wavelength for the absorption of incident light by the material in that layer.

[0029] The embodiments of the present invention also provide, as follows: Figure 1 The gain modulation method of the graphene-based dual-band detector with the structure shown is as follows: Figure 2As shown, two types of signal light are set, namely signal light A and signal light B, where signal light A is absorbed by the first light absorption layer and signal light B is absorbed by the second light absorption layer.

[0030] One of the signal light sources, signal light A and signal light B, serves as the modulation light. The modulation light alters the Fermi level of the graphene layer, causing doping of the light absorption layer (including the first and second light absorption layers), promoting the built-in electric field of the graphene, and finally generating positive / negative photocurrents.

[0031] In some embodiments, signal light A serves as modulation light, and its input frequency is lower than that of signal light B. Signal light B generates a compensated output signal based on the optical power density of modulation light A, which manifests as a significant increase or decrease in output current compared to the output current after only inputting the original signal light B.

[0032] In some embodiments, signal light B serves as modulation light, and its input frequency is lower than that of signal light A. Signal light A generates a compensated output signal based on the optical power density of modulation light B, which manifests as a significant increase or decrease in output current compared to the output current after only inputting the original signal light A.

[0033] The following embodiments of the present invention will be used in conjunction with specific examples to further demonstrate the feasibility and progressiveness of this application.

[0034] Example 1:

[0035] Add a signal light A, which falls within the visible light spectrum. Add a signal light B, which falls within the infrared light spectrum. Signal light B has a lower input frequency than signal light A, making it a modulated light. The optical power density of signal light B is also higher than that of signal light A.

[0036] Furthermore, infrared modulated light B induces p-type doping in graphene layer 2, enhancing the built-in electric field of graphene layer 2 / absorbing layer 1, and enabling electrons (the generated signal light) from the absorbing layer 1 to be effectively injected into the graphene. Infrared radiation can induce p-doping of graphene channels from the graphene layer / absorbing layer 1 interface.

[0037] Furthermore, the infrared light modulation-enhanced p-doped graphene promotes the built-in electric field of graphene, injecting more electrons into the graphene. The absorption layer 1 will dominate the photoresponse, generating a negative photocurrent, thereby increasing the responsivity of the signal light A.

[0038] Example 2:

[0039] A signal light A, belonging to the visible light range, is added. A signal light B, belonging to the infrared light range, is also added. Signal light A has a lower input frequency than signal light B, making it a modulated light. The optical power density of signal light B is greater than that of signal light A.

[0040] Furthermore, it can be seen that the modulated light A induces n-type doping in the graphene layer, reducing the built-in electric field of the graphene layer / absorber layer 3, thus effectively reducing the holes injected into the absorber layer 3 of the graphene (generated signal light). Visible light radiation can induce n-type doping in the graphene channel from the graphene layer / absorber layer 3 interface.

[0041] Furthermore, the visible light modulation-enhanced n-doped graphene promotes the built-in electric field of graphene, reduces hole injection into graphene, and causes the absorption layer 1 to dominate the photoresponse, generating a lower positive photocurrent, thereby effectively reducing the responsivity of the signal light B.

[0042] As described in Examples 1 and 2, the optical modulation method involves the mutual modulation between two wavelength systems. Optical modulation increases or decreases the responsivity, thereby achieving more effective extraction of dual-band signals.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A gain modulation method for a graphene-based dual-band detector, characterized in that, The graphene-based dual-band photodetector includes a first light-absorbing layer, a graphene layer, and a second light-absorbing layer, with the graphene layer positioned between the first and second light-absorbing layers to form a sandwich structure; a metal electrode is disposed on the surface of the graphene layer. The gain modulation method includes: The first signal light is incident on the photodetector and absorbed by the first light absorption layer to form a first graphene / light absorption layer vertical Schottky junction, and the generated photogenerated carriers enter the graphene layer. The second signal light is incident on the photodetector and absorbed by the second light absorption layer, forming a second graphene / light absorption layer B vertical Schottky junction, and the generated photogenerated carriers enter the graphene layer. The first signal light is light with different wavelengths, which passes through the first light absorption layer, the graphene layer and then the second light absorption layer; the long-wavelength portion of the first signal light is absorbed by the second light absorption layer after passing through the first light absorption layer and the graphene layer. The first signal light is visible light; The second signal light is infrared light; The photogenerated carriers generated when the first signal light and the second signal light are incident on the photodetector enter the graphene layer, causing a change in the Fermi level of the graphene layer. The graphene Fermi level changes, leading to either suppression or promotion of carrier transfer.

2. The modulation method as described in claim 1, characterized in that, The first light-absorbing layer is made of short-wavelength absorbing material and does not absorb long-wavelength light.

3. The modulation method as described in claim 1, characterized in that, The second light-absorbing layer is made of long-wavelength absorbing material and does not absorb short-wavelength light.

4. The modulation method as described in claim 1, characterized in that, The thickness of the first light-absorbing layer is greater than the length of the cutoff wavelength for the absorption of incident light by the material in that layer.

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