Amorphous gallium oxide-based thin-film transistor direct X-ray detector and its fabrication method
By designing a three-terminal structure and doping modulation of amorphous gallium oxide-based thin-film transistors, the problems of detection efficiency and response speed of existing X-ray detectors were solved, achieving X-ray detection effects with high sensitivity and low detection limit.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG FIRST MEDICAL UNIV & SHANDONG ACADEMY OF MEDICAL SCI
- Filing Date
- 2026-04-27
- Publication Date
- 2026-06-02
AI Technical Summary
Existing X-ray detectors have limitations in detection efficiency, spatial resolution, and environmental adaptability, and are also expensive to manufacture. Amorphous Ga2O3 thin films suffer from high defect density, low carrier mobility, short diffusion length, and short lifetime, which affect sensitivity, response speed, and detection limit.
A three-terminal thin-film transistor structure is adopted, and a stacked channel structure with a front channel layer and a back channel layer is designed. In2O3 with high carrier mobility is used as the front channel layer and Ga2O3 or doped Ga2O3 is used as the back channel layer. The structure is prepared by vacuum evaporation and magnetron sputtering. Source/drain electrodes are embedded to improve carrier collection efficiency, and the thin film resistivity is modulated by doping with group IIIA elements such as In and Al.
It improves the sensitivity and response speed of X-ray detectors, lowers the detection limit, enhances the signal-to-noise ratio and charge collection efficiency, suppresses dark current problems, and strengthens the environmental adaptability of devices.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor device technology, specifically relating to an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector and its fabrication method. Background Technology
[0002] X-ray detectors, as important radiation detection devices, have significant applications in medical diagnosis, environmental monitoring, security inspection, and industrial production. However, existing X-ray detectors still have many limitations in terms of detection efficiency, spatial resolution, and environmental adaptability, and their high manufacturing cost restricts their large-scale application to some extent.
[0003] Gallium oxide (Ga2O3), as a fourth-generation semiconductor material, possesses advantages such as wide bandgap, high breakdown field strength, radiation resistance, high temperature resistance, and good material stability. It can directly absorb X-rays and convert them into electrical signals, making it an ideal candidate material for direct-type X-ray detectors. Among them, amorphous Ga2O3 thin films also feature simple fabrication processes, good uniformity, ease of large-area fabrication, and excellent compatibility with planar digital readout circuits. Its low-temperature deposition process is suitable for flexible, wearable optoelectronic devices, and amorphous Ga2O3 thin-film X-ray detectors have achieved significant performance improvements, with sensitivity far exceeding that of commercial a-Se X-ray detectors (20 μC·Gy). -1 ·cm -2 ).
[0004] In the prior art, patent CN109755342A discloses a direct X-ray detector and its fabrication method. This device includes a wide-bandgap oxide thin film active layer and a first electrode and a second electrode mounted on the same side of the active layer. However, such two-ended devices typically have low gain coefficients and require a relatively thick Ga2O3 layer to absorb X-rays and generate sufficient electron-hole pairs. However, due to limitations in material transport properties, excessive thickness reduces the device's charge collection efficiency. Patent CN119181740A discloses a transistor X-ray detector and its fabrication method. This device reduces interface defects by setting a high carrier concentration interface passivation layer, improving the X-ray detector's sensitivity and enhancing the transistor's voltage stability. However, the amorphous Ga2O3 thin film used as the channel layer lacks a long-range ordered structure and exhibits high defect density, resulting in low carrier mobility, short diffusion length, and short lifetime, thus affecting the detector's sensitivity, response speed, and detection limit. Summary of the Invention
[0005] To address the problems raised in the background art, the present invention provides an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector and its fabrication method.
[0006] The technical solution of the present invention is as follows: This invention provides an amorphous gallium oxide-based thin-film transistor direct X-ray detector, which uses a substrate as the base and consists of, from bottom to top: a gate electrode, a gate insulating dielectric layer, a front channel layer, a source electrode and a drain electrode, and a back channel layer; The source electrode and drain electrode are spaced apart on the upper surface of the front channel layer; The back channel layer covers the exposed areas of the source electrode, drain electrode, and front channel layer.
[0007] Based on the amorphous gallium oxide-based thin-film transistor direct X-ray detector described above, the thickness of the front channel layer is 5-20 nm.
[0008] Based on the amorphous gallium oxide-based thin-film transistor direct X-ray detector described above, the thickness of the back channel layer is 100-1000 nm.
[0009] The present invention also provides a method for fabricating the aforementioned amorphous gallium oxide-based thin-film transistor direct-type X-ray detector, comprising the following steps: S1: The gate electrode is deposited on the substrate using vacuum evaporation technology; S2: Deposit a gate insulating dielectric layer on the surface of the gate electrode using a vacuum deposition process; S3: Deposit the front trench layer on the surface of the gate insulating dielectric layer using a magnetron sputtering process; S4: Deposit source and drain electrodes on the surface of the front channel layer using vacuum evaporation technology; S5: Deposit the back channel layer in the exposed areas of the source electrode, drain electrode, and front channel layer using a magnetron sputtering process.
[0010] Based on the fabrication method of the amorphous gallium oxide-based thin-film transistor direct X-ray detector described above, the front channel layer material is In2O3.
[0011] Furthermore, the thickness of the front channel layer is 5-20 nm.
[0012] Preferably, the process parameters of the magnetron sputtering process in S3 are: the target material is an In2O3 ceramic target, the sputtering power is 50-120W, and the substrate temperature is 25-100℃.
[0013] Based on the fabrication method of the amorphous gallium oxide-based thin-film transistor direct X-ray detector described above, the back channel layer material is Ga2O3 or Ga2O3 doped with a Group 3 element.
[0014] Furthermore, the thickness of the back channel layer is 100-1000 nm.
[0015] Preferably, the process parameters of the magnetron sputtering process in S5 are as follows: the target material is a pure Ga2O3 ceramic target or a Ga2O3 ceramic target doped with a Group 3 element, the sputtering power is 50-120W, and the substrate temperature is 25-400℃.
[0016] Beneficial effects This invention, taking into account the properties of amorphous Ga2O3 thin film materials and device structure, firstly utilizes the high gain characteristics of a three-terminal thin-film transistor structure to lower the detection limit of the device while improving the signal-to-noise ratio. Secondly, a stacked channel structure formed by a front channel layer and a back channel layer is designed. Combined with the high carrier mobility characteristics of the front channel layer, the lateral carrier transport capability is enhanced, and the charge collection efficiency is improved, thereby increasing the sensitivity and response speed of the device. Furthermore, embedding the source / drain electrodes between the front channel layer and the back channel layer further improves the collection efficiency of lateral carriers by the source / drain electrodes.
[0017] This invention modulates the resistivity of amorphous Ga2O3 thin films by doping with Group IIIA elements such as In and Al, effectively suppressing the high dark current problem caused by shallow donor levels, and improving the response speed of the detector. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the structure of an amorphous gallium oxide-based thin-film transistor direct X-ray detector according to the present invention, wherein 1-gate electrode, 2-gate insulating dielectric layer, 3-front channel layer, 4-source electrode, 5-drain electrode, and 6-back channel layer.
[0019] Figure 2 This is a schematic diagram of the band structure of an amorphous gallium oxide-based thin-film transistor direct X-ray detector before (a) and after (b) contact between the In2O3 front channel layer and the Al-doped Ga2O3 back channel layer in Embodiment 2 of the present invention. Detailed Implementation
[0020] The following examples are intended to illustrate the present invention, and not to further limit the invention.
[0021] This invention provides an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector, such as... Figure 1 With the substrate as the base, from bottom to top, the layers are: gate electrode 1, gate insulating dielectric layer 2, front channel layer 3, source electrode 4 and drain electrode 5, and back channel layer 6. The source electrode 4 and the drain electrode 5 are disposed alternately on the upper surface of the front channel layer 3; The back channel layer 6 covers the exposed areas of the source electrode 4, the drain electrode 5, and the front channel layer 3.
[0022] The thickness of the front channel layer 3 is 5-20 nm.
[0023] The thickness of the back channel layer 6 is 100-1000 nm.
[0024] Amorphous Ga2O3 thin films lack long-range ordered structures and exhibit high defect density, resulting in low carrier mobility, short diffusion length, and short lifetime, which in turn affects the detector's sensitivity, response speed, and detection limit. This invention, considering the material properties of amorphous Ga2O3 thin films and the device structure, firstly utilizes the high-gain characteristics of a three-terminal thin-film transistor structure to lower the device's detection limit and improve the signal-to-noise ratio. Secondly, a stacked channel structure formed by a front channel layer and a back channel layer is designed. Combined with the high carrier mobility of the front channel layer, this enhances the lateral carrier transport capability and improves charge collection efficiency, thereby increasing the device's sensitivity and response speed. Furthermore, embedding the source / drain electrodes between the front and back channel layers further improves the lateral carrier collection efficiency of the source / drain electrodes.
[0025] The present invention also provides a method for fabricating the aforementioned amorphous gallium oxide-based thin-film transistor direct-type X-ray detector, comprising the following steps: S1: The gate electrode 1 is deposited on the substrate using vacuum evaporation technology.
[0026] The gate electrode 1 is any one or a combination of at least two of Ti, Au, Cr, ITO, Al, Cu, and heavily doped Si.
[0027] Preferably, the vacuum evaporation technology is thermal evaporation, electron beam evaporation, or magnetron sputtering.
[0028] S2: A gate insulating dielectric layer 2 is deposited on the surface of the gate electrode 1 using a vacuum deposition process.
[0029] The gate insulating dielectric layer 2 is any one or a combination of at least two of SiO2, Al2O3, and HfO2.
[0030] Preferably, the vacuum deposition process is atomic layer deposition, plasma-enhanced atomic layer deposition, plasma-enhanced chemical vapor deposition, or thermal oxidation.
[0031] S3: Deposit the front trench layer 3 on the surface of the gate insulating dielectric layer 2 by magnetron sputtering.
[0032] The front channel layer 3 is made of high-mobility oxide In2O3. Based on the stacked channel structure, the high carrier mobility of In2O3 is used to enhance the lateral transport capability of carriers.
[0033] Furthermore, the high-mobility oxide In2O3 is grown by radio frequency magnetron sputtering. The process parameters of the magnetron sputtering process are as follows: the target material is an In2O3 ceramic target, the sputtering power is 50-120W, the substrate temperature is 25-100℃, and the thickness of the front channel layer 3 is 5-20nm.
[0034] S4: Source electrode 4 and drain electrode 5 are deposited on the surface of front channel layer 3 using vacuum evaporation technology.
[0035] The source electrode 4 and the drain electrode 5 are any one or a combination of at least two of Ti, Au, Cr, ITO, Al, and Cu, and the source electrode 4 and the drain electrode 5 are rectangular or interdigitated.
[0036] S5: Deposit the back trench layer 6 in the exposed areas of the source electrode 4, drain electrode 5 and front trench layer 3 using a magnetron sputtering process.
[0037] The back trench layer 6 is made of Ga2O3 or Ga2O3 doped with a third group element (such as In, Al, etc.).
[0038] Furthermore, Ga2O3 or Ga2O3 doped with a Group 3 element is grown by radio frequency magnetron sputtering. The process parameters of the magnetron sputtering process are as follows: the target material is a pure Ga2O3 ceramic target or a Ga2O3 ceramic target doped with a Group 3 element, the sputtering power is 50-120W, the substrate temperature is 25-400℃, and the thickness of the back channel layer 6 is 100-1000nm.
[0039] The presence of shallow donor levels in amorphous Ga2O3 thin films results in a high free electron concentration and low resistivity, leading to high dark current and slow response speed in the devices. This invention modulates the amorphous Ga2O3 thin film by doping with Group IIIA elements such as In and Al, thereby increasing the film resistivity, effectively suppressing the high dark current problem caused by shallow donor levels, and simultaneously improving the detector's response speed.
[0040] In addition, the X-ray detector is obtained by patterning the gate electrode 1, the front channel layer 3, the source electrode 4 and the drain electrode 5 and the back channel layer 6 using ultraviolet lithography and lift-off processes.
[0041] Example 1 This embodiment provides an amorphous gallium oxide-based thin-film transistor direct X-ray detector, which uses a substrate as the base and consists of, from bottom to top: an ITO gate electrode 1, a SiO2 gate insulating dielectric layer 2, an In2O3 front channel layer 3, an ITO source electrode 4 and a drain electrode 5, and a Ga2O3 back channel layer 6; the ITO source electrode 4 and the drain electrode 5 are disposed alternately on the upper surface of the In2O3 front channel layer 3; the Ga2O3 back channel layer 6 covers the exposed areas of the source electrode 4, the drain electrode 5, and the front channel layer 3.
[0042] The preparation method is as follows: S1: ITO gate electrode 1 with a thickness of 150nm is deposited on the substrate by magnetron sputtering, and patterning is completed by ultraviolet lithography and lift-off process.
[0043] S2: A SiO2 gate insulating dielectric layer 2 with a thickness of 30 nm is deposited on the surface of the gate electrode 1 using plasma-enhanced chemical vapor deposition.
[0044] S3: An In2O3 thin film is sputtered and deposited on the surface of the SiO2 gate insulating dielectric layer 2 by magnetic radio frequency magnetron sputtering process to form the In2O3 front channel layer 3; wherein the sputtering power is 50W, the substrate temperature is 25℃, the deposition thickness is 5nm, and the patterning is completed by ultraviolet lithography and lift-off process.
[0045] S4: ITO source electrode 4 and drain electrode 5 with a thickness of 150nm are deposited on the surface of In2O3 front channel layer 3 using magnetron sputtering technology, and rectangular patterning is completed by ultraviolet lithography and lift-off process. S5: A Ga2O3 thin film is deposited and grown in the exposed areas of the ITO source electrode 4, drain electrode 5 and In2O3 front channel layer 3 by radio frequency magnetron sputtering to form a Ga2O3 back channel layer 6; wherein the target material is a pure Ga2O3 ceramic target, the sputtering power is 50W, the substrate temperature is 25℃, the deposition thickness is 100nm, and the patterning is completed by ultraviolet lithography and lift-off process to obtain the X-ray detector.
[0046] Example 2 This embodiment provides an amorphous gallium oxide-based thin-film transistor direct X-ray detector. Using a substrate as the base, the structure from bottom to top consists of: an ITO gate electrode 1, a SiO2 gate insulating dielectric layer 2, an In2O3 front channel layer 3, an ITO source electrode 4 and a drain electrode 5, and an Al-doped Ga2O3 back channel layer 6. The ITO source electrode 4 and drain electrode 5 are spaced apart on the upper surface of the In2O3 front channel layer 3. The Al-doped Ga2O3 back channel layer 6 covers the exposed areas of the source electrode 4, the drain electrode 5, and the front channel layer 3.
[0047] The preparation method is as follows: S1: ITO gate electrode 1 with a thickness of 150nm is deposited on the substrate by magnetron sputtering, and patterning is completed by ultraviolet lithography and lift-off process.
[0048] S2: A SiO2 gate insulating dielectric layer 2 with a thickness of 30 nm is deposited on the surface of the gate electrode 1 using plasma-enhanced chemical vapor deposition.
[0049] S3: An In2O3 thin film is sputtered and deposited on the surface of the SiO2 gate insulating dielectric layer 2 by magnetic radio frequency magnetron sputtering process to form the In2O3 front channel layer 3; wherein the sputtering power is 50W, the substrate temperature is 25℃, the deposition thickness is 5nm, and the patterning is completed by ultraviolet lithography and lift-off process.
[0050] S4: ITO source electrode 4 and drain electrode 5 with a thickness of 150nm are deposited on the surface of In2O3 front channel layer 3 using magnetron sputtering technology, and rectangular patterning is completed by ultraviolet lithography and lift-off process. S5: An Al-doped Ga2O3 (denoted as Ga2O3:Al, Al doping amount 5at%) thin film is deposited and grown in the exposed areas of the ITO source electrode 4, drain electrode 5 and In2O3 front channel layer 3 by radio frequency magnetron sputtering process to form an Al-doped Ga2O3 back channel layer 6; wherein the target material is an Al-doped Ga2O3 ceramic target, the sputtering power is 50W, the substrate temperature is 25℃, the deposition thickness is 100nm, and the patterning is completed by ultraviolet lithography and lift-off process to obtain the X-ray detector.
[0051] Using high-mobility In2O3 as the front channel layer and Ga2O3:Al as the back channel layer, since Ga2O3:Al (conduction band bottom E) C ≈-2.78eV, vacuum energy level is 0eV) and In2O3 (E C There is a conduction band offset of 0.86 eV (≈-3.64 eV), such as... Figure 2 As shown, an effective electronic barrier is formed at the interface, allowing electrons in the Ga2O3:Al layer to be transported unidirectionally to the In2O3 layer. At the same time, the high mobility of In2O3 is utilized to significantly enhance the lateral transport capability of charge carriers, thereby enhancing the charge collection capability.
[0052] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. An amorphous gallium oxide-based thin-film transistor direct-type X-ray detector, characterized in that, Using the substrate as the base, from bottom to top, the layers are: gate electrode (1), gate insulating dielectric layer (2), front channel layer (3), source electrode (4) and drain electrode (5), and back channel layer (6). The source electrode (4) and the drain electrode (5) are disposed alternately on the upper surface of the front channel layer (3); The back channel layer (6) covers the exposed areas of the source electrode (4), the drain electrode (5), and the front channel layer (3).
2. The amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 1, characterized in that, The thickness of the front channel layer (3) is 5-20 nm.
3. The amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 1, characterized in that, The thickness of the back channel layer (6) is 100-1000 nm.
4. A method for fabricating an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector as described in claim 1, characterized in that, Includes the following steps: S1: The gate electrode is deposited on the substrate using vacuum evaporation technology (1). S2: A gate insulating dielectric layer (2) is deposited on the surface of the gate electrode (1) using a vacuum deposition process. S3: Deposit the front trench layer (3) on the surface of the gate insulating dielectric layer (2) by magnetron sputtering. S4: Deposit source electrode (4) and drain electrode (5) on the surface of front channel layer (3) using vacuum evaporation technology; S5: Deposit back channel layer (6) in the exposed areas of source electrode (4), drain electrode (5) and front channel layer (3) by magnetron sputtering.
5. The method for fabricating an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 4, characterized in that, The material of the front channel layer (3) is In2O3.
6. The method for fabricating an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 5, characterized in that, The thickness of the front channel layer (3) is 5-20 nm.
7. The method for fabricating an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 6, characterized in that, The process parameters for the magnetron sputtering process described in S3 are as follows: the target material is an In2O3 ceramic target, the sputtering power is 50-120W, and the substrate temperature is 25-100℃.
8. The method for fabricating an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 4, characterized in that, The back trench layer (6) is made of Ga2O3 or Ga2O3 doped with a third group element.
9. The method for fabricating an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 8, characterized in that, The thickness of the back channel layer (6) is 100-1000 nm.
10. The method for fabricating an amorphous gallium oxide-based thin-film transistor direct-type X-ray detector according to claim 9, characterized in that, The process parameters for the magnetron sputtering process described in S5 are as follows: the target material is a pure Ga2O3 ceramic target or a Ga2O3 ceramic target doped with a third main element, the sputtering power is 50-120W, and the substrate temperature is 25-400℃.