High-sensitivity gallium oxide ultraviolet detector and preparation method and application thereof

Abstract

The present invention discloses a high-sensitivity gallium oxide ultraviolet detector, its preparation method and application. The high-sensitivity gallium oxide ultraviolet detector includes an n-type gallium oxide channel layer, a p-type photo-floating gate, a patterned photo-floating gate dielectric layer, a first electrode and a second electrode; the p-type photo-floating gate is disposed on the n-type gallium oxide channel layer, the patterned photo-floating gate dielectric layer is disposed between the p-type photo-floating gate and the n-type gallium oxide channel layer and is completely covered by the p-type photo-floating gate, the first electrode and the second electrode are disposed on the n-type gallium oxide channel layer and form an ohmic contact with the n-type gallium oxide channel layer; wherein, the p-type impurity concentration in the p-type photo-floating gate is much greater than the n-type impurity concentration in the n-type gallium oxide channel layer, the thickness of the patterned photo-floating gate dielectric layer is 10 nm to 30 nm, the duty cycle is 10% to 90%, and the width of the depletion region of the n-type gallium oxide channel layer under illumination changes with the change of the duty cycle of the patterned photo-floating gate dielectric layer.

Description

Technical Field

[0001] This invention relates in particular to a high-sensitivity gallium oxide ultraviolet detector, its preparation method and application, belonging to the field of optoelectronic device technology. Background Technology

[0002] Due to the absorption effect of the ozone layer, background ultraviolet light in the UVC band (<280nm) is almost non-existent in nature, which gives UVC band detection extremely high signal-to-noise ratio and low false alarm rate. UVC band ultraviolet light is also known as solar-blind ultraviolet light, and solar-blind ultraviolet detection has already shown great application potential in optical imaging, ozone hole detection, missile guidance and early warning, secure space communication, and corona detection. Ga2O3, as a natural solar-blind ultraviolet material, boasts a high signal-to-noise ratio of 10... 5 cm- 1 Its light absorption coefficient and the ability to obtain single crystals via the Czochralski method make it a highly promising candidate for solar-blind ultraviolet detectors.

[0003] Ga2O3-based solar-blind ultraviolet detectors primarily employ two-terminal structures, such as photoconductive and Schottky diode types, metal-semiconductor-metal (MSM) types, and pn heterojunction types, as well as three-terminal structures, such as MOSFETs. Photoconductive types, due to their large dark current, do not meet the low-power requirements of detector applications. Schottky diode, MSM, and pn heterojunction structures all introduce depletion regions to effectively reduce dark current. However, the width of the depletion region remains essentially constant under illumination, meaning that photogenerated carriers must pass through a large potential barrier or a depletion region with extremely high resistance before being collected by the electrodes. Potential barriers and depletion regions often limit the photocurrent of two-terminal devices, resulting in responsivity typically ranging from tens to hundreds of amperes per watt (A / W), and a photo-dark current ratio (PDCR) that is difficult to exceed 10. 6 To achieve higher responsivity and high sensitivity for weak light detection, researchers have proposed MOSFET-type ultraviolet detectors. This type of detector exhibits extremely high gain and responsivity, with a photocurrent-to-dark-current ratio significantly greater than 10. 8 The responsiveness has even exceeded 10. 6 A / W. However, three-terminal devices significantly increase the complexity of the readout circuit, especially for large-area detector arrays, where the large number of leads significantly increases the risk of short circuits and open circuits between leads. Therefore, there is an urgent need to propose a two-terminal ultraviolet detector with high responsivity.

[0004] Currently, some scholars have proposed using Ga2O3 MOSFETs as ultraviolet detectors. This structure provides the ability to control the channel through the gate voltage and possesses intrinsic gain, resulting in extremely high responsivity. The specific technical solution is as follows:

[0005] (1) A Ga2O3 buffer layer and a Si-doped Ga2O3 epitaxial film were respectively epitaxially grown on a high-resistivity Ga2O3 single crystal substrate; the high-resistivity Ga2O3 single crystal substrate was an Fe-doped substrate, to prevent vertical leakage and improve vertical breakdown voltage; the Ga2O3 buffer layer had a thickness of 1 μm; the Si-doped Ga2O3 film had a thickness of 200 nm and a doping concentration of 9.5 × 10⁻⁶. 17 cm- 3 .

[0006] (2) The Ga2O3 groove is etched using inductively coupled plasma (ICP) etching technology, with a groove depth of 180nm. The function of the groove is to increase the control of the gate on the channel, thereby realizing the enhancement device.

[0007] (3) A 30 nm Al2O3 film is deposited in the groove using atomic layer deposition (ALD) to reduce gate leakage.

[0008] (4) Source-drain ohmic contact preparation: The electrode is prepared using a Ti / Au (20 / 80nm) bilayer metal and combined with rapid annealing technology to form an alloy.

[0009] (5) Schottky gate metal fabrication: The electrode is made of Ni / Au (20 / 80nm) bilayer metal.

[0010] The device operates as follows: In the absence of light, the concentration of charge carriers in the channel can be controlled via the gate, thus enabling the device to turn on and off; when the device is off, the current is extremely low. For example... Figure 2a , Figure 2b As shown, if illumination is applied, the Ga2O3 in the channel will generate a large number of photogenerated carriers, which will be separated and collected under the influence of the source-drain voltage, thus achieving a large photocurrent. However, due to the gate voltage, the band structure below the gate does not change under illumination, resulting in no significant reduction in the depletion region. Therefore, whether in the dark or under illumination, the carriers in the device must pass through a large depletion region. Since the resistance in the depletion region is extremely high, it significantly limits the current magnitude of the device, especially the photocurrent.

[0011] However, using Ga2O3 MOSFETs as ultraviolet detectors has the following drawbacks:

[0012] a. Three-port devices significantly increase lead count: Compared to MSM, Schottky, or heterojunction diodes, MOSFET devices add a gate to control the channel current. However, in large-area optical imaging systems, three-port devices significantly increase lead count and wiring difficulties, increasing the risk of short circuits and open circuits, as well as parasitic parameters.

[0013] b. Failure to utilize the photovoltaic effect: Due to the gate voltage, the potential difference between the area below the gate and the source / drain is constant (depending on the external voltage), so the band structure of the gate metal to Ga2O3 does not change when the device switches from dark to light, that is, the depletion region below the gate is fixed. Figure 3a The simulation-extracted channel electron concentration distribution under Schottky gate control is shown. (Example:) Figure 3a , Figure 3b As shown, the device is in a negative gate bias, i.e., in the off state. At this time, electrons below the gate are depleted, resulting in a large depletion region, which remains essentially unchanged under 254nm illumination. The energy band and electron concentration distribution below the gate are shown in the figure. Figure 3b As shown, the energy bands can completely overlap with and without illumination, with only a slight increase in electron concentration. Essentially, this device still utilizes the generation of photogenerated carriers under illumination and their separation under an external voltage, i.e., the photoconductive effect. The depletion region below the gate reduces both the dark-state current and the current under illumination.

[0014] c. Complex manufacturing process: Using Ga2O3 MOSFETs as ultraviolet detectors requires etching grooves to achieve enhancement mode. However, grooves prepared by etching are prone to leakage current and other problems, thus requiring a more challenging Al2O3 dielectric layer. Furthermore, the buffer layer in this device is designed to withstand extremely high voltages and does not significantly improve photodetection performance. Summary of the Invention

[0015] The main objective of this invention is to provide a high-sensitivity p-type optical floating gate transistor (OFGT) ultraviolet detector, its fabrication method, and its applications. Compared with a three-port MOSFET, this OFGT uses a p-type material as the photogate and has only two ports, source and drain, simplifying the design of the readout circuit. At the same time, the device fully considers the relationship between light intensity and the open-circuit voltage of the pn heterojunction, and uses the photogenerated electromotive force to achieve a linear increase in the photocurrent with light intensity and precise control of the photoconductivity gain, thereby overcoming the shortcomings of the prior art.

[0016] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0017] The first aspect of the present invention provides a high-sensitivity gallium oxide ultraviolet detector, which includes: an n-type gallium oxide channel layer, a p-type optical grating, a patterned optical grating dielectric layer, and a first electrode and a second electrode;

[0018] The p-type optical grating is disposed on the n-type gallium oxide channel layer, and the patterned optical grating dielectric layer is disposed between the p-type optical grating and the n-type gallium oxide channel layer and is completely covered by the p-type optical grating. The first electrode and the second electrode are disposed on the n-type gallium oxide channel layer and form an ohmic contact with the n-type gallium oxide channel layer. The p-type impurity concentration in the p-type optical grating is much greater than the n-type impurity concentration in the n-type gallium oxide channel layer. The thickness of the patterned optical grating dielectric layer is 10 nm to 30 nm, and the duty cycle is 10% to 90%. The width of the depletion region of the n-type gallium oxide channel layer under illumination changes with the duty cycle of the patterned optical grating dielectric layer.

[0019] In the dark state, the p-type optical floating gate and the n-type gallium oxide channel layer form a pn heterojunction, and the electrons in the n-type gallium oxide channel layer below the p-type optical floating gate are fully depleted. When the device is irradiated with ultraviolet light, the depletion region of the pn heterojunction narrows, and the electron concentration at the bottom of the n-type gallium oxide channel layer gradually recovers, thereby realizing the turn-on of the device.

[0020] A second aspect of this invention provides a method for fabricating a high-sensitivity gallium oxide ultraviolet detector, comprising:

[0021] An n-type gallium oxide channel layer is provided, and a patterned optical floating gate dielectric layer is formed in a first region of the n-type gallium oxide channel layer. The thickness of the patterned optical floating gate dielectric layer is 10 nm to 30 nm, and the duty cycle is 10% to 90%.

[0022] A p-type optical grating is formed in a first region of the n-type gallium oxide channel layer, such that the p-type optical grating completely covers the patterned optical grating dielectric layer, and the p-type impurity concentration in the p-type optical grating is much greater than the n-type impurity concentration in the n-type gallium oxide channel layer.

[0023] A first electrode and a second electrode are formed in a second region of the n-type gallium oxide channel layer, and the first electrode and the second electrode form an ohmic contact with the n-type gallium oxide channel layer. The second region is disposed on both sides of the first region.

[0024] In the dark state, the p-type optical floating gate and the n-type gallium oxide channel layer form a pn heterojunction, and the electrons in the n-type gallium oxide channel layer below the p-type optical floating gate are fully depleted. When the device is irradiated with ultraviolet light, the depletion region of the pn heterojunction narrows, and the electron concentration at the bottom of the n-type gallium oxide channel layer gradually recovers, thereby realizing the turn-on of the device.

[0025] A third aspect of the present invention provides a photoelectric detection device comprising at least one of the aforementioned high-sensitivity gallium oxide ultraviolet detectors.

[0026] Compared with the prior art, the advantages of the present invention include:

[0027] The high-sensitivity gallium oxide ultraviolet detector device provided in this invention has a double-ended structure compared to traditional MOSFET devices, which can significantly reduce the lead density and circuit design complexity during readout circuit design.

[0028] The present invention provides a high-sensitivity gallium oxide ultraviolet detector device, which can achieve higher photoconductivity gain compared with traditional MOSFET devices or currently reported ultraviolet detectors. At the same time, the photoconductivity gain can be precisely and flexibly controlled by changing the duty cycle of the optical floating gate dielectric layer, thereby coping with various complex detection environments. Attached Figure Description

[0029] Figure 1 This describes the fabrication process of a grooved Ga2O3 MOSFET ultraviolet detector.

[0030] Figure 2 is a schematic diagram of the device structure under dark and ultraviolet light conditions;

[0031] Figure 3a These are electron concentration distribution diagrams of the device under dark conditions and 254nm ultraviolet light illumination;

[0032] Figure 3b It is along Figure 3a The energy band and electron concentration profile curves along the direction of the dashed line 1;

[0033] Figure 4 This is a schematic diagram of the structure of an OFGT ultraviolet detector with high responsivity and controllable photoconductivity gain provided in a typical embodiment of the present invention.

[0034] Figure 5 This is a top view of an OFGT ultraviolet detector with high responsivity and controllable photoconductivity gain provided in a typical embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram of the fabrication process of an OFGT ultraviolet detector with high responsivity and controllable photoconductivity gain, provided in a typical embodiment of the present invention.

[0036] Figure 7a This is a schematic diagram of the interface of a p-NiO / Ga2O3 OFGT device provided in a typical embodiment of the present invention;

[0037] Figure 7b This is a contour plot of the electron concentration distribution of a p-NiO / Ga2O3 OFGT device in the dark state, provided in a typical embodiment of the present invention.

[0038] Figure 7c This is a contour plot of electron concentration distribution of a p-NiO / Ga2O3 OFGT device under 254nm ultraviolet light, provided in a typical embodiment of the present invention.

[0039] Figure 8a , Figure 8b These are, respectively, a typical embodiment of the present invention, a p-NiO / Ga2O3 OFGT device under dark state and 254nm ultraviolet light illumination, electron concentration contour plot under the action of patterned optically floating Al2O3 gate dielectric layer;

[0040] Figure 9a , Figure 9b These are electron concentration contour plots for a p-NiO / Ga2O3 OFGT device with a patterned optically floating Al2O3 gate dielectric layer and without a patterned optically floating Al2O3 gate dielectric layer, provided in a typical embodiment of the present invention.

[0041] Figure 9c This is a typical embodiment of the p-NiO / Ga2O3 OFGT device provided by the present invention. Figure 9a , Figure 9b Electron concentration distribution curves of dashed lines A and B;

[0042] Figure 9d This is a comparison of light and dark currents before and after introducing a patterned optically floating Al2O3 gate dielectric layer in a p-NiO / Ga2O3 OFGT device, provided in a typical embodiment of the present invention. Detailed Implementation

[0043] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate the technical solution, its implementation process, and its principles.

[0044] The first aspect of the present invention provides a high-sensitivity gallium oxide ultraviolet detector, which includes: an n-type gallium oxide channel layer, a p-type optical grating, a patterned optical grating dielectric layer, and a first electrode and a second electrode;

[0045] The p-type optical grating is disposed on the n-type gallium oxide channel layer, and the patterned optical grating dielectric layer is disposed between the p-type optical grating and the n-type gallium oxide channel layer and is completely covered by the p-type optical grating. The first electrode and the second electrode are disposed on the n-type gallium oxide channel layer and form an ohmic contact with the n-type gallium oxide channel layer. The p-type impurity concentration in the p-type optical grating is much greater than the n-type impurity concentration in the n-type gallium oxide channel layer. The thickness of the patterned optical grating dielectric layer is 10 nm to 30 nm, and the duty cycle is 10% to 90%. The width of the depletion region of the n-type gallium oxide channel layer under illumination changes with the duty cycle of the patterned optical grating dielectric layer.

[0046] In the dark state, the p-type optical floating gate and the n-type gallium oxide channel layer form a pn heterojunction, and the electrons in the n-type gallium oxide channel layer below the p-type optical floating gate are fully depleted. When the device is irradiated with ultraviolet light, the depletion region of the pn heterojunction narrows, and the electron concentration at the bottom of the n-type gallium oxide channel layer gradually recovers, thereby realizing the turn-on of the device.

[0047] Furthermore, the concentration of p-type impurities in the p-type optical grating is 1-2 orders of magnitude higher than the concentration of n-type impurities in the n-type gallium oxide channel layer.

[0048] Furthermore, the n-type impurity concentration within the n-type gallium oxide channel layer is 5 × 10⁻⁶. 16 cm -3 ~5×10 17 cm -3 The concentration of p-type impurities within the p-type optical grating is 5 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 .

[0049] Furthermore, the material of the p-type optical grating includes, but is not limited to, p-NiO, p-GaN, p-Si, or p-In2O3.

[0050] Furthermore, the thickness of the p-type optical grating is 80nm to 150nm.

[0051] Furthermore, the thickness of the n-type gallium oxide channel layer is 100nm to 200nm.

[0052] Furthermore, the patterned optical levitation grating dielectric layer includes multiple spaced dielectric layer structures, and the dielectric layer structures are regular hexagonal structures.

[0053] Furthermore, the material of the patterned optical levitation grating dielectric layer includes Al2O3, SiO2, Si3N4 or AlN, but is not limited to these.

[0054] A second aspect of this invention provides a method for fabricating a high-sensitivity gallium oxide ultraviolet detector, comprising:

[0055] An n-type gallium oxide channel layer is provided, and a patterned optical floating gate dielectric layer is formed in a first region of the n-type gallium oxide channel layer. The thickness of the patterned optical floating gate dielectric layer is 10 nm to 30 nm, and the duty cycle is 10% to 90%.

[0056] A p-type optical grating is formed in a first region of the n-type gallium oxide channel layer, such that the p-type optical grating completely covers the patterned optical grating dielectric layer, and the p-type impurity concentration in the p-type optical grating is much greater than the n-type impurity concentration in the n-type gallium oxide channel layer.

[0057] A first electrode and a second electrode are formed in a second region of the n-type gallium oxide channel layer, and the first electrode and the second electrode form an ohmic contact with the n-type gallium oxide channel layer. The second region is disposed on both sides of the first region.

[0058] In the dark state, the p-type optical floating gate and the n-type gallium oxide channel layer form a pn heterojunction, and the electrons in the n-type gallium oxide channel layer below the p-type optical floating gate are fully depleted. When the device is irradiated with ultraviolet light, the depletion region of the pn heterojunction narrows, and the electron concentration at the bottom of the n-type gallium oxide channel layer gradually recovers, thereby realizing the turn-on of the device.

[0059] Furthermore, the concentration of p-type impurities in the p-type optical grating is 1-2 orders of magnitude higher than the concentration of n-type impurities in the n-type gallium oxide channel layer.

[0060] Furthermore, the n-type impurity concentration within the n-type gallium oxide channel layer is 5 × 10⁻⁶. 16 cm- 3 ~5×10 17 cm- 3 The concentration of p-type impurities within the p-type optical grating is 5 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 .

[0061] Furthermore, the material of the p-type optical grating includes, but is not limited to, p-NiO, p-GaN, p-Si, or p-In2O3.

[0062] Furthermore, the thickness of the p-type optical grating is 80nm to 150nm.

[0063] Furthermore, the thickness of the n-type gallium oxide channel layer is 100nm to 200nm.

[0064] Furthermore, the patterned optical levitation grating dielectric layer includes multiple spaced dielectric layer structures, and the dielectric layer structures are regular hexagonal structures.

[0065] Furthermore, the material of the patterned optical levitation grating dielectric layer includes Al2O3, SiO2, Si3N4 or AlN, but is not limited to these.

[0066] A third aspect of the present invention provides a photoelectric detection device comprising at least one of the aforementioned high-sensitivity gallium oxide ultraviolet detectors.

[0067] The following will further explain the technical solution, its implementation process and principle in conjunction with the accompanying drawings and specific implementation examples. Unless otherwise specified, the epitaxial growth process and equipment, photolithography, etching process and equipment, lift-off process, etc. used in the embodiments of the present invention are all known in the art and are not specifically limited here.

[0068] For a more specific implementation plan, please refer to Figure 4 An OFGT ultraviolet detector with high responsivity and controllable photoconductivity gain includes a substrate, an n-type gallium oxide channel layer, a p-type optical grating, a patterned optical grating dielectric layer, and a first electrode and a second electrode. The n-type gallium oxide channel layer is disposed on the substrate, the p-type optical grating is disposed on the n-type gallium oxide channel layer, the patterned optical grating dielectric layer is disposed between the p-type optical grating and the n-type gallium oxide channel layer and is completely covered by the p-type optical grating, and the first electrode and the second electrode are disposed on the n-type gallium oxide channel layer and form an ohmic contact with the n-type gallium oxide channel layer.

[0069] Specifically, the substrate can be a wide bandgap substrate material such as sapphire, diamond, or AlN; a substrate with a bandgap greater than Ga2O3 allows for FPA (Fixed-Package Interconnect) to be used for flip-chip bonding and readout circuit interconnection. Commercially available sapphire substrates (both c-plane sapphire and sapphire with off-axis orientation) can reduce device costs.

[0070] Specifically, the n-type gallium oxide channel layer can be a Ga2O3 thin film doped with shallow donor impurities such as Si, Sn, or H. The thickness of the n-type gallium oxide channel layer is 100 nm to 200 nm, and the doping concentration is 5 × 10⁻⁶. 16 cm- 3 ~5×10 17 cm- 3 The thickness and doping concentration of the n-type gallium oxide channel layer are among the key parameters for achieving high responsivity, low dark current, and precise control of photoconductivity gain in OFGT.

[0071] Specifically, the p-type optical grating can be a p-NiO, p-GaN, p-Si, or p-In2O3 thin film, with a thickness of 80 nm to 150 nm and a doping concentration of 5 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 To ensure that the OFGT can reach the cutoff state in the dark, the doping concentration of the p-type optical floating gate needs to be much greater than that of the n-type gallium oxide channel layer, so that the depletion region extends towards the n-type gallium oxide channel layer. It should be noted that if the p-type optical floating gate is too thick, it will easily absorb too much ultraviolet light, causing the cutoff edge of the OFGT photoresponse to redshift. If it is too thin, it will be difficult to deplete the Ga2O3 channel. Understandably, part of the p-type optical floating gate is distributed in the gaps of the patterned optical floating gate dielectric layer and is in direct contact with the n-type gallium oxide channel layer, while another part covers the patterned optical floating gate dielectric layer.

[0072] Specifically, the material of the patterned optical levitation grating dielectric layer can be Al2O3, SiO2, Si3N4 or AlN, with a thickness of 10 nm to 30 nm and a duty cycle adjustable from 10% to 90% (the effect of adjustment outside this range will not be obvious).

[0073] Specifically, the inventors of this case discovered that the patterned optical grating dielectric layer can significantly affect the photovoltaic effect of the p-type optical grating / n-type gallium oxide channel layer, i.e., the depletion region width. This invention, through simulation, revealed the relationship between the photoconductivity gain of the OFGT and the thickness and duty cycle of the patterned optical grating dielectric layer: G = -(Dc - Dc0)^2 + Gm * (1 - (h - h0)^2), where G and Dc are variables: G is the photoconductivity gain, Dc is the duty cycle of the patterned optical grating dielectric layer, h is the thickness of the patterned optical grating dielectric layer, h0 is the optimal thickness of the patterned optical grating dielectric layer, Dc0 is the optimal duty cycle of the patterned optical grating dielectric layer, and Gm is the maximum gain of the patterned optical grating dielectric layer. It should be noted that the duty cycle represents the percentage of the total length of the patterned optical grating dielectric layer along the x-axis to the grating length, where the grating length is the length of the p-type optical grating along the x-axis, and the grating length was set to 1 μm in the simulation.

[0074] Simulation results show that an excessively large thickness (h) of the patterned optical levitation gate dielectric layer leads to excessive dark current and reduced gain, while an excessively small thickness results in severe channel depletion by the p-type gate, reducing photocurrent and gain. In other words, h determines the upper limit of gain. Similarly, the duty cycle of the patterned optical levitation gate dielectric layer also has an optimal value, approximately 50%. Specifically, the carrier concentration in the p-type region typically needs to be 1-2 orders of magnitude higher than that in the n-type region. If the thickness of the patterned optical levitation gate dielectric layer is too thin, such as below 10 nm, its influence on the depletion region becomes very weak, and the patterned optical levitation gate dielectric layer loses its gain control function. If the thickness of the patterned optical levitation gate dielectric layer is too large, i.e., greater than 30 nm, it will severely weaken the effect of the p-type gate, resulting in excessive current and noise in the dark state. Maximum gain can be achieved when the thickness of the patterned optical levitation gate dielectric layer is 20 nm. Specifically, the relationship between duty cycle and gain follows a parabolic model. When the duty cycle is 100%, the current will reach the μA level, meaning that the patterned optical grating dielectric layer has completely weakened the depletion effect of the p-type grating on the channel. If the duty cycle is 0, i.e. there is no patterned optical grating dielectric layer, the photocurrent is lower, i.e., the gain is lower. From the parabolic model that the duty cycle and gain satisfy, it can be seen that the gain is the maximum when the duty cycle is 50%.

[0075] Specifically, based on the three-dimensional planar arrangement of the patterned optical levitation grating dielectric layer, the ideal structure for the patterned optical levitation grating dielectric layer is a regular hexagon. The regular hexagonal structure is best suited for adjusting the spatial distribution law and has the most uniform effect on the electric field distribution. Specifically, as shown... Figure 5 As shown.

[0076] It is worth mentioning that the growth of the optical floating grating dielectric layer is not dependent on the growth method, that is, it can be prepared by chemical vapor deposition, sputtering, atomic layer deposition and other growth schemes.

[0077] Specifically, the first and second electrodes can be Ti (20-50 nm) / Au (120-150 nm) ohmic metals.

[0078] The following provides an feasible device fabrication scheme. It is worth noting that this scheme is not unique, and alternative methods or materials will be described in the scheme.

[0079] Please see Figure 6 A method for fabricating an OFGT ultraviolet detector with high responsivity and controllable photoconductivity gain may include the following steps:

[0080] (1) Epitaxy and doping of Ga2O3 thin film on sapphire substrate:

[0081] The sapphire substrate can be either c-plane or beveled with an off-axis angle; after organic cleaning of the sapphire substrate, MOCVD epitaxy and doping of Ga2O3 thin films are performed; the thickness of the Ga2O3 thin film is 100nm~200nm, and the doping concentration is controlled at 5×10⁻⁶. 16 cm- 3 ~5×10 17 cm- 3 The epitaxial growth method of Ga2O3 film can be replaced by commercially mature growth schemes such as MBE, ALD, HVPE, and PECVD; the donor impurity can be a shallow donor impurity such as Si, Sn, or H.

[0082] (2) Preparation of patterned Al2O3 dielectric layer:

[0083] Atomic layer deposition (ALD) is used to deposit Al2O3 films with a thickness of 10 nm to 30 nm on the surface of Ga2O3 films. The Al2O3 films are then patterned using inductively coupled plasma (ICP) etching. At this point, the duty cycle of the Al2O3 dielectric layer can be designed to obtain different photoconductivity gains for different application requirements. The deposition method of the Al2O3 film can be replaced by commercially mature solutions such as PECVD and sputtering. In addition to etching techniques such as ICP and RIE, patterning can also be achieved through lift-off techniques.

[0084] (3) Fabrication of p-NiO optical grating:

[0085] p-type NiO thin films with patterned Al2O3 dielectric layers were prepared using radio frequency sputtering technology. The doping concentration of the p-type NiO thin films was 5 × 10⁻⁶. 17 cm- 3 ~1×10 19 cm- 3 ; p-NiO optical levitation gates of different gate lengths were prepared by ICP etching technology; in addition to sputtering, epitaxy and other technologies, p-type NiO thin films can also be obtained by oxidizing metallic Ni; in addition to etching technology, p-NiO optical levitation gates can also be prepared by lift-off technology; it is worth mentioning that p-NiO thin films can be replaced by other p-type materials, including p-GaN, p-Si, p-In2O3, etc.

[0086] (4) Preparation of ohmic contact electrodes:

[0087] Ti (20-50 nm) / Au (120-150 nm) bilayer metal was deposited on Ga2O3 thin film using an electron beam evaporation apparatus and annealed in a nitrogen atmosphere for 1 min at a temperature of 475 °C.

[0088] To illustrate the advantages of OFGT over traditional MOSFET-type ultraviolet detectors with fixed gate voltage, the following will elaborate on the working principle and photoconductive modulation mechanism of the device.

[0089] The working principle of the device provided in this embodiment of the invention: In order to clearly explain the working principle of OFGT, the electron concentration distribution in the cross section of OFGT was simulated using the commercial simulation software TCAD SILVACO. Figure 7a A cross-sectional schematic diagram of a p-NiO / Ga2O3 OFGT device is shown. In the simulation, the thickness of the p-NiO optical grating is set to 100 nm, and the doping concentration is set to 5 × 10⁻⁶. 18 cm -3 The thickness of the n-Ga2O3 channel layer was set to 150 nm, and the doping concentration was set to 1 × 10⁻⁶. 17 cm -3 That is, it meets the design scope of the above process flow. For example... Figure 7b As shown, in the dark state, since the p-NiO optical floating gate and the n-Ga2O3 channel layer form a pn heterojunction, and the doping concentration of the p-NiO optical floating gate is much greater than that of the n-Ga2O3 channel layer, the electrons in the n-Ga2O3 channel layer below the p-NiO optical floating gate are fully depleted, resulting in an extremely low electron concentration; the resistance of the depletion region is extremely high, therefore the current is extremely small; when the device is subjected to 254nm ultraviolet light, since no electrodes are designed on the p-NiO optical floating gate, the potential is not fixed, i.e., it is in a floating state, thus the depletion region of p-NiO / Ga2O3 narrows under the influence of the photogenerated electromotive force. The direction of the photogenerated electromotive force is that the potential at the p-NiO end is higher than that at the n-Ga2O3 end, which is equivalent to applying a turn-on voltage to the p-NiO optical floating gate. This phenomenon is manifested in OFGT as follows: Figure 7c As shown, the electron concentration at the bottom of the Ga2O3 channel gradually recovers, the channel resistance decreases, and thus the device is turned on. Therefore, compared with traditional MOSFET devices, the core working mechanism of the OFGT provided in this embodiment of the invention lies in the change of the depletion region in the channel under illumination. Since the change of the depletion region is usually extremely sensitive, the photocurrent of the device can be significantly greater than the dark current.

[0090] Photoconductivity Gain Control Principle: As described in the above description of the device's working principle, the photoconductivity gain of the OFGT provided by this invention mainly comes from changes in the depletion region. However, the device provided by this invention can only achieve the initial dark-state depletion region design by adjusting the pn doping concentration of p-NiO / Ga2O3, leaving a gap in the control scheme for the depletion region under illumination. Therefore, this invention controls the size of the depletion region under illumination by inserting a patterned optical floating grating dielectric layer at the p-NiO / n-Ga2O3 interface. An Al2O3 optical floating grating dielectric layer with a thickness of 20 nm and a duty cycle of 60% was designed in the simulation to illustrate its function. The effects of optical floating grating dielectric layers with different duty cycles can be analyzed by analogy. Figure 8a As shown, after inserting the Al2O3 optical grating dielectric layer, the Ga2O3 channel remains in a depleted state in the dark, the same as the result without the Al2O3 optical grating dielectric layer. However, under ultraviolet light with a wavelength of 254 nm, the electron concentration below the Al2O3 optical grating dielectric layer is significantly increased, as shown in the figure. Figure 8b As shown. Therefore, by adjusting the duty cycle of the Al2O3 optical grating dielectric layer, the depletion region distribution under illumination can be flexibly changed, thereby controlling the photoconductivity gain of the OFGT.

[0091] To further verify the effect of patterned Al2O3 optical levitation grating dielectric layer on photoconductivity gain, this invention extracted the electron concentration in the channel and the photoresponse current of the p-NiO / Ga2O3 OFGT device through simulation. Figure 9a , Figure 9b As shown, the electron concentration of the patterned Al2O3 optical grating dielectric layer was simulated under the same illumination intensity, and the electron concentration distribution along the dashed lines A and B was extracted respectively. Figure 9c As shown, the electron concentration along dashed line B is significantly greater than that along dashed line A, fully demonstrating that the patterned Al2O3 optical grating dielectric layer can enhance the photoconductivity effect. Figure 9d The photocurrent and dark current of the p-NiO / Ga2O3 OFGT device before and after the introduction of a patterned Al2O3 optical floating gate dielectric layer are shown. Figure 9d It can be seen that after introducing a patterned Al2O3 optical grating dielectric layer, the dark current of OFGT remains basically unchanged, while the photocurrent is significantly improved.

[0092] This invention provides a high-sensitivity gallium oxide ultraviolet detector device. The p-type optical floating gate has no electrodes; the device only has anode and cathode, forming a two-terminal structure. Unlike MOSFETs, which require a gate voltage to turn on or off, this high-sensitivity gallium oxide ultraviolet detector device cannot have any voltage applied to its p-type optical floating gate, nor can it be grounded. Instead, it relies on the photogenerated electromotive force (EMF) under illumination to turn on the device. The p-type optical floating gate in this invention fully utilizes the photogenerated EMF; that is, illumination is equivalent to applying a positive turn-on voltage to the p-type optical floating gate. In other words, this high-sensitivity gallium oxide ultraviolet detector device converts the effect of illumination into the effect of an external voltage. Furthermore, this high-sensitivity gallium oxide ultraviolet detector device can also control the photoconductivity gain of the OFGT through a patterned floating gate dielectric layer.

[0093] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-sensitivity gallium oxide ultraviolet detector, characterized in that, include: The structure consists of an n-type gallium oxide channel layer, a p-type optical grating, a patterned optical grating dielectric layer, and a first electrode and a second electrode. The p-type optical grating is disposed on the n-type gallium oxide channel layer, and the patterned optical grating dielectric layer is disposed between the p-type optical grating and the n-type gallium oxide channel layer and is completely covered by the p-type optical grating. The first electrode and the second electrode are disposed on the n-type gallium oxide channel layer and form an ohmic contact with the n-type gallium oxide channel layer. The p-type impurity concentration in the p-type optical grating is much greater than the n-type impurity concentration in the n-type gallium oxide channel layer. The thickness of the patterned optical grating dielectric layer is 10 nm to 30 nm, and the duty cycle is 10% to 90%. The width of the depletion region of the n-type gallium oxide channel layer under illumination changes with the duty cycle of the patterned optical grating dielectric layer. In the dark state, the p-type optical floating gate and the n-type gallium oxide channel layer form a pn heterojunction, and the electrons in the n-type gallium oxide channel layer below the p-type optical floating gate are fully depleted. When the device is irradiated with ultraviolet light, the depletion region of the pn heterojunction narrows, and the electron concentration at the bottom of the n-type gallium oxide channel layer gradually recovers, thereby realizing the turn-on of the device.

2. The high-sensitivity gallium oxide ultraviolet detector according to claim 1, characterized in that: The p-type impurity concentration in the p-type optical grating is 1-2 orders of magnitude higher than the n-type impurity concentration in the n-type gallium oxide channel layer; preferably, the n-type impurity concentration in the n-type gallium oxide channel layer is 5 × 10⁻⁶. 16 cm -3 ~5×10 17 cm -3 The concentration of p-type impurities within the p-type optical grating is 5 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 .

3. The high-sensitivity gallium oxide ultraviolet detector according to claim 1, characterized in that: The material of the p-type optical grating includes p-NiO, p-GaN, p-Si, or p-In2O3; Preferably, the thickness of the p-type optical grating is 80nm to 150nm.

4. The high-sensitivity gallium oxide ultraviolet detector according to claim 1, characterized in that: The thickness of the n-type gallium oxide channel layer is 100 nm to 200 nm.

5. The high-sensitivity gallium oxide ultraviolet detector according to claim 1, characterized in that: The patterned optical levitation grating dielectric layer includes multiple spaced dielectric layer structures, wherein the dielectric layer structure is a regular hexagonal structure; and / or, the material of the patterned optical levitation grating dielectric layer includes Al2O3, SiO2, Si3N4 or AlN.

6. A method for fabricating a high-sensitivity gallium oxide ultraviolet detector, characterized in that, include: An n-type gallium oxide channel layer is provided, and a patterned optical floating gate dielectric layer is formed in a first region of the n-type gallium oxide channel layer. The thickness of the patterned optical floating gate dielectric layer is 10 nm to 30 nm, and the duty cycle is 10% to 90%. A p-type optical grating is formed in a first region of the n-type gallium oxide channel layer, such that the p-type optical grating completely covers the patterned optical grating dielectric layer, and the p-type impurity concentration in the p-type optical grating is much greater than the n-type impurity concentration in the n-type gallium oxide channel layer. A first electrode and a second electrode are formed in a second region of the n-type gallium oxide channel layer, and the first electrode and the second electrode form an ohmic contact with the n-type gallium oxide channel layer. The second region is disposed on both sides of the first region. In the dark state, the p-type optical floating gate and the n-type gallium oxide channel layer form a pn heterojunction, and the electrons in the n-type gallium oxide channel layer below the p-type optical floating gate are fully depleted. When the device is irradiated with ultraviolet light, the depletion region of the pn heterojunction narrows, and the electron concentration at the bottom of the n-type gallium oxide channel layer gradually recovers, thereby realizing the turn-on of the device.

7. The method for fabricating a high-sensitivity gallium oxide ultraviolet detector according to claim 6, characterized in that: The p-type impurity concentration in the p-type optical grating is 1-2 orders of magnitude higher than the n-type impurity concentration in the n-type gallium oxide channel layer; preferably, the n-type impurity concentration in the n-type gallium oxide channel layer is 5 × 10⁻⁶. 16 cm -3 ~5×10 17 cm -3 The concentration of p-type impurities within the p-type optical grating is 5 × 10⁻⁶. 17 cm -3 ~1×10 19 cm -3 .

8. The method for fabricating a high-sensitivity gallium oxide ultraviolet detector according to claim 7, characterized in that: The material of the p-type optical levitation grating includes p-NiO, p-GaN, p-Si or p-In2O3, and preferably, the thickness of the p-type optical levitation grating is 80nm to 150nm; And / or, the thickness of the n-type gallium oxide channel layer is 100nm to 200nm.

9. The method for fabricating a high-sensitivity gallium oxide ultraviolet detector according to claim 7, characterized in that: The patterned optical levitation grating dielectric layer includes multiple spaced dielectric layer structures, wherein the dielectric layer structure is a regular hexagonal structure; and / or, the material of the patterned optical levitation grating dielectric layer includes Al2O3, SiO2, Si3N4 or AlN.

10. A photoelectric detection device, characterized in that... It includes at least one high-sensitivity gallium oxide ultraviolet detector as described in any one of claims 1-6.

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