A color perception device based on a semiconductor thin film with a gradually varying bandgap and a preparation method thereof

Abstract

The present invention belongs to the technical field of semiconductor photodetectors, and specifically relates to a color perception device based on a semiconductor thin film with a gradually varying bandgap and a preparation method thereof. The color perception device of the present invention includes two discrete devices that output two signals. Device 1 uses a semiconductor thin film with a gradually varying bandgap as the photosensitive layer, and the output signal is related to the photon energy and optical flux of the optical signal. Device 2 uses a semiconductor thin film with a relatively narrow bandgap as the photosensitive layer, and the output signal is only related to the optical flux of the optical signal. By combining the two signals, the average photon energy, i.e., the average wavelength, of the optical signal is obtained, realizing color perception. The present invention can reduce the preparation process and cost; by changing the proportion of semiconductor elements in the photosensitive layer, a semiconductor thin film with a gradually varying bandgap is prepared to achieve the response of optical signals in a relatively wide wavelength range; the gradient of the gradual change is modulated by utilizing the fine control characteristics of atomic layer deposition to achieve more precise color resolution. The device of the present invention can be used in the fields of optical detection, intelligent sensing, and the Internet of Things, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor photodetectors, and particularly relates to a bandgap-graded semiconductor thin film color sensing device and a preparation method thereof. Background Art

[0002] Light is an important information carrier in nature. Detecting optical signals and converting them into electrical signals enables people to better understand the information they carry, thereby expanding the ways of information exchange. In an optoelectronic system, a photodetector is like the "eye" of the optoelectronic system, capturing external optical signals and converting them into electrical signals for subsequent signal processing. The applications of photodetectors involve communication, imaging, security, the Internet of Things, artificial vision systems, etc., and are closely related to the development of human society.

[0003] Currently existing photodetectors can be classified into thermoelectric type and optoelectronic semiconductor type from the working principle. The thermoelectric type photodetector converts an optical signal into a thermal signal and then converts the thermal signal into an electrical signal. Therefore, it measures the optical power density of the optical signal. The optoelectronic semiconductor type photodetector converts an optical signal into an optical exciton and then into a current signal. Therefore, it measures the total energy of the optical signal. It can be seen that current photodetectors cannot achieve color perception of optical signals. To achieve color perception, the commonly adopted method is to prepare a series of devices that only respond to narrow-band optical signals and assemble them into a microchip. By complementing the detected optical bands of different devices, color perception of optical signals can be achieved. However, this scheme has extremely high process requirements and is not conducive to large-scale promotion as a commercial optical signal color sensor.

[0004] Therefore, it is necessary to develop a method for preparing an optical signal color sensing device with a simple preparation process and excellent performance to avoid the above problems existing in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a bandgap-graded semiconductor thin film color sensing device with a simple preparation process and excellent performance and a preparation method thereof.

[0006] The bandgap-graded semiconductor thin film color sensing device provided by the present invention, as shown in Figure 1 is composed of two discrete devices juxtaposed through a common insulating substrate, outputting two signals; Device 1 uses a bandgap-graded semiconductor thin film as the photosensitive layer, and its output signal is related to both the photon energy (i.e., optical wavelength) and the optical flux (i.e., light intensity) of the optical signal. Device 2 uses a semiconductor thin film with a relatively narrow bandgap as the photosensitive layer, and its output signal is only related to the optical flux of the optical signal. By combining these two signals, the average photon energy (i.e., average wavelength) of the optical signal can be obtained, thereby achieving color perception.

[0007] The structure of Device 1 from bottom to top is as follows: an insulating substrate, two-terminal electrodes, and a semiconductor thin film with a gradually varying bandgap (photosensitive layer). The structure of Device 2 from bottom to top is as follows: an insulating substrate, two-terminal electrodes, and a semiconductor thin film with a relatively narrow bandgap (photosensitive layer).

[0008] Preferably, for the semiconductor photosensitive layer thin film with a gradually varying bandgap, in the thickness direction, its bandgap gradually increases from bottom to top, so that optical signals of different wavelengths can excite the optical responses of semiconductor thin films with different thicknesses. Since the semiconductor with a wider bandgap is located at the upper part of the thin film, it does not affect the light absorption of the semiconductor thin film with a relatively narrow bandgap at the lower part. The semiconductor thin film with a gradually varying bandgap is achieved by adjusting the gradual change of the composition element ratio of the semiconductor. The semiconductor materials include but are not limited to Al x Zn y O, V x Zn y O, ZnO x N y . Among them, the elemental subscript parameters X and Y represent the content of the element.

[0009] Preferably, the narrow-bandgap semiconductor thin film is the semiconductor corresponding to the narrowest part of the bandgap in the gradually varying semiconductor thin film.

[0010] Preferably, the insulating substrate material is a silicon substrate, a glass substrate on which an insulating thin film such as SiO2, Al2O3, HfO2, ZrO2 is grown, or a flexible substrate of a polymer thin film.

[0011] Preferably, the electrode material can be one of Cr / Au, Ti / Au, Ni / Au, ITO, Mo.

[0012] The present invention also provides a preparation method for the above-mentioned color perception device with a semiconductor thin film having a gradually varying bandgap. The specific steps are as follows:

[0013] Step 1: Substrate cleaning. The substrate (including a silicon substrate, a glass substrate on which an insulating thin film is grown, or a flexible substrate of a polymer thin film) is successively placed in acetone and isopropyl alcohol solutions, and ultrasonically cleaned (for 30 - 35 minutes) respectively, then rinsed with deionized water and dried with a high-pressure nitrogen gun.

[0014] Step 2: Define the electrode size through ultraviolet lithography, prepare the electrode thin film by electron beam evaporation, with a thickness range of 30 - 50 nm, and finally strip off the excess photoresist.

[0015] Step 3: For Device 1, grow a bandgap-graded semiconductor thin film by atomic layer deposition with a thickness range of 30 - 50 nm. Each cycle includes: introducing a mixed precursor, purging with nitrogen, introducing a co-reactant precursor, and purging with nitrogen. As the number of cycles increases, gradually change the ratio of the components of the semiconductor material mixed precursor to achieve a gradient change in the film composition elements in the thickness direction. Then define its size by ultraviolet lithography and etch it to form Device 1 with the bottom electrode.

[0016] For Device 2, grow a narrow-bandgap semiconductor thin film by atomic layer deposition with a thickness range of 20 - 30 nm. Each cycle includes: introducing a mixed precursor, purging with nitrogen, introducing a co-reactant precursor, and purging with nitrogen. Then define its size by ultraviolet lithography and etch it to form the target Device 2 with the bottom electrode.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] In the present invention, a single device can achieve the color perception function of a chip-level spectral detection device, reducing the preparation process and cost; by changing the ratio of elements in the photosensitive layer, a bandgap-graded semiconductor thin film is prepared, which can respond to optical signals in a relatively wide wavelength range; using the fine control characteristics of atomic layer deposition to modulate the gradient, more precise color resolution can be achieved. The devices of the present invention can be used in fields such as optical detection, intelligent sensing, and the Internet of Things. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of a bandgap-graded semiconductor thin film color perception device designed by the present invention.

[0020] Figure 2 It is a schematic diagram of a complete ALD growth cycle of a bandgap-graded Al x Zn y O thin film designed by the present invention.

[0021] Figure 3 It is a schematic diagram of the output current of a bandgap-graded semiconductor color perception device designed by the present invention changing with light intensity.

[0022] Figure 4 It is a schematic diagram of the output current of a bandgap-graded semiconductor color perception device designed by the present invention changing with wavelength. DETAILED DESCRIPTION OF THE INVENTION

[0023] The following further describes the present invention through specific embodiments with reference to the accompanying drawings. These embodiments are only used to illustrate the present invention and do not limit the protection scope of the present invention.

[0024] Embodiment 1

[0025] Device fabrication process: Fabricate a color sensing device with a bandgap-graded semiconductor thin film as shown in Figure 1 Figure

[0026] The structure of the bandgap-graded semiconductor color sensing device is as shown in Figure 1 Figure, from bottom to top in sequence: low-resistance silicon 10, insulating layer 20, two-terminal electrodes 30, bandgap-graded semiconductor 40, and narrow-bandgap semiconductor 50. The specific fabrication process is as follows:

[0027] (1) The substrate uses a low-resistance silicon substrate with a 30 nm SiO2 surface. That is, at this time, the low-resistance silicon 10 is a heavily doped P-type silicon with a resistivity < 0.005 Ω•cm, and the insulating layer 20 is 30 nm of SiO2. Before use, it is successively placed in acetone and isopropyl alcohol solutions for ultrasonic cleaning for 30 minutes each, then rinsed with deionized water and dried with a high-pressure nitrogen gun;

[0028] (2) Negative photoresist is exposed to ultraviolet light under a mask to form a pattern. A bilayer film of 10nm Ti / 20nm Au is prepared by electron beam evaporation as the bottom two-terminal electrodes, and the excess photoresist is removed by acetone using the lift-off process;

[0029] (3) For device 1, it consists of low-resistance silicon 10, insulating layer 20, two-terminal electrodes 30, and bandgap-graded semiconductor 40. Among them, the growth of the bandgap-graded semiconductor thin film is carried out by atomic layer deposition. The thickness range is 30 - 50 nm. Each cycle period of atomic layer deposition includes: introducing a mixed precursor, purging with nitrogen, introducing the co-reactant precursor of this semiconductor material, and purging with nitrogen. And at different cycles, the proportion of the precursor components of this semiconductor material is varied. For device 2, it consists of low-resistance silicon 10, insulating layer 20, two-terminal electrodes 30, and narrow-bandgap semiconductor 50. Among them, the narrow-bandgap semiconductor corresponds to the part with the narrowest bandgap in the graded semiconductor. That is, after the bandgap-graded semiconductor thin film grows to a thickness of 20 - 30 nm, the pattern is defined using photoresist and partial areas are blocked. Continue atomic layer deposition until completion, then remove the photoresist. The unblocked area forms the bandgap-graded semiconductor thin film (i.e., the photosensitive layer of device 1), and the blocked area forms the narrow-bandgap semiconductor thin film (i.e., the photosensitive layer of device 2). After etching, it forms device 1 and device 2 with the bottom electrode. The width / length dimensions of the device are both 100 um / 10 um.

[0030] Thus, the fabrication of the bandgap-graded semiconductor color sensing device as shown in Figure 1 Figure is completed.

[0031] Example 2

[0032] Example of fabricating a bandgap-graded semiconductor thin film: Fabricate Al by atomic layer deposition x Zn yO film as an example.

[0033] Figure 2 The invention grows Al with a band gap gradient x Zn y Schematic diagram of a complete ALD growth cycle of O film. It includes introducing a mixed precursor of trimethylaluminum and diethylzinc into the chamber at the same time to form a molecular layer on the substrate surface and introducing deionized water to form Al x Zn y O material. The above process specifically includes the following steps:

[0034] S1, the chamber is heated to 200°C and the pipe is heated to 100°C to prevent the precursor from condensing and adsorbing on the chamber wall and the pipe. A mixed precursor of trimethylaluminum and diethylzinc is introduced into the reaction chamber at the same time, and the precursor is allowed to stay in the reaction chamber for a period of time to be adsorbed on the substrate surface;

[0035] S2, introducing inert gas N2 into the reaction chamber to remove excess precursor;

[0036] S3, deionized water is introduced into the cavity to react with the mixed precursor to form a layer of Al on the surface x Zn y OMaterial;

[0037] S4, inert gas N2 is introduced into the reaction chamber to purge the reaction byproducts and excess deionized water, thus completing the ALD deposition of Al x Zn y A complete reaction cycle of O film;

[0038] S5, after increasing the ratio of trimethylaluminum in the mixed precursor in S1, the steps S2-S5 are cycled n (n=1, 2, 3...) times to obtain Al2O3 with a certain thickness. x Zn y O film.

[0039] This completes the preparation of Al with bandgap gradient by atomic layer deposition. x Zn y O film.

[0040] Example 3

[0041] Performance demonstration: Perception of the colors of monochromatic and polychromatic light.

[0042] Since the output signals of device 1 and device 2 are both related to the luminous flux (i.e., light intensity) of the optical signal, it can be expected that when the voltage at both ends and the optical wavelength of the optical signal remain unchanged, the output current of device 1 and device 2 should be positively linearly correlated with the light intensity. Figure 3 A schematic diagram of a curve showing the variation of the output current of the bandgap gradient semiconductor color sensing device designed for the present invention with the light intensity.

[0043] As shown in the schematic diagram Figure 3 As shown, we can use linear equations (1) and (2) to express the relationship between the output current and luminous flux of device 1 and device 2 respectively:

[0044] I1 = a·φ+b (1)

[0045] I2 = c·φ+d (2)

[0046] Among them, I1 and I2 are the output currents of devices 1 and 2 respectively, φ is the luminous flux of the optical signal, and a, b, c, and d are the corresponding linear equation constant parameters.

[0047] Since different wavelengths of the optical signal can stimulate responses of different thicknesses of the photosensitive layer in device 1, but have no significant effect on the output signal of device 2, it can be expected that when the voltage at both ends and the luminous flux of the optical signal remain unchanged, the output current of device 1 should be negatively linearly correlated with the wavelength of light, and the output current of device 2 does not change with the wavelength of light. Figure 4 A schematic diagram of a curve showing how the output current of the bandgap gradient semiconductor color sensing device designed for the present invention changes with the wavelength of light.

[0048] As indicated Figure 4 As shown, we can use linear equations (3) and (4) to express the relationship between the output current and the optical wavelength of device 1 and device 2 respectively:

[0049] I1 = e·λ+f (3)

[0050] I2 = g (4)

[0051] Wherein, I1 and I2 are the output currents of devices 1 and 2 respectively, λ is the wavelength of the optical signal, and e, f, and g are the constant parameters of the corresponding linear equation.

[0052] Considering that the output current of device 1 is only related to the luminous flux of the optical signal, and the output current of device 2 is only related to the photon energy and luminous flux (i.e., light intensity) of the optical signal, the relationship between the output current of device 1 and device 2 and the luminous flux and wavelength can be obtained by combining equations (1), (2), (3), and (4):

[0053] I1 = e·λ+f+a·(φ-φ0) (5)

[0054] I2 = g+c·(φ-φ0) (6)

[0055] Among them, φ0 is the luminous flux constant to be determined in the actual test, and the other parameters are the constant parameters mentioned above.

[0056] Therefore, for monochromatic light, the output currents of devices 1 and 2 can give its luminous flux and wavelength; for polychromatic light, the output currents of devices 1 and 2 can give its statistical luminous flux and average wavelength. Thus, the color perception of monochromatic and polychromatic light is achieved.

[0057] So far, the color perception demonstration of the designed bandgap-graded semiconductor color perception device for unknown monochromatic and polychromatic light of the present invention is completed.

[0058] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A color perception device of a semiconductor thin film with a gradually changing bandgap, characterized in that, It is composed of two discrete devices juxtaposed through a common insulating substrate, and two signals are output; among them, device 1 uses a semiconductor thin film with a gradually varying bandgap as the photosensitive layer, and its output signal is related to the photon energy of the optical signal, i.e., the optical wavelength and the optical flux, i.e., the light intensity; device 2 uses a semiconductor thin film with a relatively narrow bandgap as the photosensitive layer, and its output signal is only related to the optical flux of the optical signal; by combining these two signals, the average photon energy of the optical signal, i.e., the average wavelength, is obtained, thereby realizing color perception; where: The structure of device 1 from bottom to top is successively: an insulating substrate, two end electrodes, and a semiconductor thin film with a gradually varying bandgap; the structure of device 2 from bottom to top is successively: an insulating substrate, two end electrodes, and a semiconductor thin film with a relatively narrow bandgap; For the semiconductor photosensitive layer thin film with a gradually varying bandgap, in the thickness direction, its bandgap gradually increases from bottom to top, so that optical signals with different wavelengths can excite the optical responses of semiconductor thin films with different thicknesses; The material of the semiconductor thin film with a relatively narrow bandgap is the same as that of the semiconductor thin film with the narrowest bandgap in the semiconductor thin film with a gradually varying bandgap; The bandgap-graded semiconductor thin film is achieved by regulating the gradual change of the composition element ratio of the semiconductor, and the material is selected from Al x Zn y O, V x Zn y O, ZnO x N y , where the element subscripts X and Y represent the content of the element.

2. The color perception device of the bandgap-graded semiconductor thin film according to claim 1, wherein The insulating substrate material is a silicon substrate with an insulating film grown thereon, a glass substrate, or a flexible substrate of a polymer film.

3. The color perception device of the bandgap-graded semiconductor thin film according to claim 2, characterized in that, The insulating film is selected from SiO2, Al2O3, HfO2, ZrO2.

4. The color perception device of the bandgap-graded semiconductor thin film according to claim 3, wherein The electrode material is selected from one of Cr / Au, Ti / Au, Ni / Au, ITO, Mo.

5. A method for preparing a color perception device of a semiconductor thin film with a gradually changing bandgap as described in any one of claims 1-4, characterized in that, The specific steps are as follows: Step 1: Substrate cleaning: The substrate is successively placed in acetone and isopropyl alcohol solutions, ultrasonically cleaned respectively, then rinsed with deionized water and blown dry with a high-pressure nitrogen gun; Step 2: Define the electrode size through ultraviolet lithography, prepare the electrode thin film by electron beam evaporation, with a thickness range of 30 - 50 nm, and finally strip off the excess photoresist; Step 3: For device 1, grow the semiconductor thin film with a gradually varying bandgap by atomic layer deposition, with a thickness range of 30 - 50 nm; each cycle includes: introducing a mixed precursor, purging with nitrogen, introducing a co-reactant precursor, purging with nitrogen; and as the number of cycles increases, gradually change the proportion of the semiconductor material precursor components to achieve the variation of the film composition elements in the thickness direction; then define its size through ultraviolet lithography and etch it to form device 1 with the bottom electrode; For device 2, grow the semiconductor thin film with a relatively narrow bandgap by atomic layer deposition, with a thickness range of 20 - 30 nm; each cycle includes: introducing a mixed precursor, purging with nitrogen, introducing a co-reactant precursor, purging with nitrogen; then define its size through ultraviolet lithography and etch it to form device 2 with the bottom electrode.

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