Gallium Oxide Films Research Articles

Enhanced electrical properties of pulsed Sn-doped (-201) β-Ga2O3 thin films via MOCVD homoepitaxy

Pulsed Sn doping (PSD) homoepitaxial gallium oxide (Ga2O3) films were deposited on (-201) β-Ga2O3 substrates using metal-organic chemical vapor deposition (MOCVD). The study aims to optimize Sn doping conditions to enhance the electrical properties of β-Ga2O3 films. The influence of Sn pulse width (ranging from 0.1 min to 0.3 min) on the morphology, structure, and electrical properties of the film was investigated. The Full Width at Half Maximum (FWHM) of the (-201) crystal plane rocking curve for all doped films is <50 arcsec, indicating high crystal quality. At a Sn pulse width of 0.2 min, we achieve the optimal balance between doping efficiency and crystal quality, resulting in a resistivity of 0.0487 Ω·cm, an electron mobility of 63.5 cm2/V·s, and a carrier concentration of 1.82 × 1018 cm-3. Compared to continuous Sn doping, PSD results in approximately 157 % increase in carrier concentration and 99 % increase in electron mobility. The application of PSD allows sufficient diffusion time for Sn atoms to effectively incorporate into the film, signifying a crucial advancement in enhancing the film's electrical properties and reducing the cost of the metal organic doping source.

Performance investigation of silicon nitride (SiNx) layer doped with twin thin films of gallium and zinc oxide for solar cell

Performance investigation of silicon nitride (SiNx) layer doped with twin thin films of gallium and zinc oxide for solar cell

Temperature modulation enables in situ growth of gallium oxide nanostructures on thin films exhibiting diverse morphologies

In this study, we successfully synthesized three gallium oxide thin films on (0001)-faceted Al2O3 substrates using hydrogen-reduced chemical vapor deposition (CVD) at different deposition temperatures, resulting in distinct morphologies and crystalline phases. These films consist of two pure-phase β-Ga2O3 films and one mixed-phase film comprising both β- and ε-Ga2O3 phases. The mixed-phase samples were subsequently annealed at high temperatures to obtain pure-phase β-Ga2O3 thin films. Furthermore, by precisely controlling the growth temperature, we achieved in-situ formation of Ga2O3 nanostructures (nanowires and nanoribbons) on the surface of the β-Ga2O3 thin films. The presence of different dominant crystal planes in the samples was confirmed through X-ray diffraction analysis (XRD) for verification purposes. In directly grown β-Ga2O3 films, the (−201) plane emerged as the primary crystallographic plane, while both the (−201) and (401) planes dominated in β-Ga2O3 films obtained via ε-Ga2O3 film annealing. Raman spectroscopy findings further supported these observations regarding the crystalline phase of the films as observed through XRD analysis. Scanning electron microscopy (SEM) images revealed distinct film morphologies resulting from variations in deposition temperatures. A flatter surface was observed when a higher proportion of ε-Ga2O3 was present in the film, however, regular cracking occurred after annealing. Atomic Force Microscope (AFM) images demonstrated that at a deposition temperature of 800 °C, regular steps were present on the film's surface. Mixed-phase films exhibited hillock morphology that disappeared after annealing, leading to a decrease in the surface roughness in root mean square (RMS) value. By elevating the growth temperature, a significantly enhanced density of gallium oxide nanoribbons can be seamlessly integrated onto the film surface. The transferred nanoribbons exhibit an ultra-thin profile with a minimum thickness of merely 12 nm, rendering them more slender and economically advantageous in comparison to conventional mechanical stripping methods. This study presents a CVD-based approach for growing gallium oxide thin films with varying morphologies by employing temperature modulation and demonstrates an innovative one-step method for growing nanostructures on gallium oxide films in situ, providing valuable insights for future device development involving gallium oxide.

High-performance of low temperature solution-processed P-channel CuGaO thin film transistors

The exploration of p-type metal-oxide semiconductors (MOS) has garnered growing interest, particularly for their potential applications in next-generation optoelectronic devices, display backplanes, and low-power consumption complementary MOS (CMOS) circuits. Here, we introduced low-temperature solution-processed copper gallium oxide (CuGaO) films for p-channel thin-film transistors (TFTs). Hall Effect measurements confirmed the p-type conduction of CuGaO, revealing a conductivity and mobility of 3.76 ×10−2 S/cm and 7.89 cm2V–1s–1, respectively. The p-channel CuGaO-250 TFT demonstrated a field-effect mobility (μFE) of 1.24 cm2V–1s–1, the lowest subthreshold swing (SS) of 519 mV/dec, and an ON/OFF current ratio (ION/IOFF) of ∼104 at a low operating voltage. The notable improvement in TFT performance can be attributed to the quality of the CuGaO-250 film, a smooth surface morphology, and a reduction of interfacial traps between the semiconductor and the gate insulator. Hence, low-temperature fabrication of the p-channel CuGaO TFT holds promise for implementing metal oxide-based TFT and complementary metal oxide semiconductor (CMOS) circuits in next-generation displays.

Reduction of oxygen vacancies in Mg–N codoped Ga2O3 films for improving solar-blind UV photodetectors performance

Solar-blind photodetectors based on gallium oxide (Ga2O3) have shown possibilities in optical imaging, spatial communication, and other fields. The high oxygen vacancy (VO) content inherent in Ga2O3 film would inevitably result in poor photoelectric detection capability. This work suggests using a codoping for reducing VO concentrations in Ga2O3 films. In a N2O atmosphere, magnesium and nitrogen codoped gallium oxide (Mg–N:Ga2O3) films were grown using the pulsed laser deposition (PLD) technique on (0001) sapphire substrates. It is possible to produce codoped Ga2O3 thin films with low oxygen vacancy density and high crystalline quality by thoroughly examining and optimizing preparation conditions. Metal-semiconductor-metal (MSM) photodetectors were constructed using both pristine and Mg–N codoped Ga2O3 thin films as the active layer. The photodetector with a codoped active layer outperforms those with pristine Ga2O3, with a quick decay time of 20 ms, a high sensitivity of 2.61 × 105, and a high responsivity of 0.191 A/W under 254 nm UV light irradiation, highlighting the significance of the VO concentration decrease in the application of Ga2O3-based solar-blind photodetectors.

High-performance a-Ga2O3 solar-blind photodetectors by pulsed magnetron sputtering deposition

Solar-blind photodetectors (SBPDs) based on the ultrawide-bandgap semiconductor Ga2O3 have gained attention due to their potential applications in both military and civilian domains. As technology advances, photodetectors are being improved to achieve better energy efficiency, smaller size, and better performance. Solar-blind photodetectors based on a metal-semiconductor-metal structure of amorphous gallium oxide (a-Ga2O3) films were fabricated by pulsed magnetron sputtering deposition (PSD). The photodetector based on amorphous gallium oxide has a responsivity of 71.52 A/W, a fast rising and falling response time of less than 200 ms, a photo-to-dark current ratio (PDCR) of 6.52 × 104, and an external quantum efficiency of 34 526.62%. PSD-prepared gallium oxide SBPDs demonstrate a cost-effective room temperature method for growing gallium oxide and show the advantages of growing gallium oxide.

DUV optoelectronic bionic synapse based on the MOCVD-deposited amorphous gallium oxide film

Optoelectronic bionic synapses, integrating sensing and processing capabilities, help to break through the limitations of von Neumann structure and are promising in smart sensors, AI robots etc. fields. Here, we fabricated a deep ultraviolet (DUV) optoelectronic bionic synapse with an amorphous gallium oxide (a-GaOx) film deposited by metal–organic chemical vapor deposition (MOCVD). DUV illumination pulses could be facilely written into the bionic synapse, and the written information exhibits non-volatility. By manipulating the illumination pulse number, the pulse width, and the pulse power density, the synapse is capable of transitioning from short-term memory (STM) to long-term memory (LTM), effectively emulating the learning-memory behavior of human brains.

The Energy Level Alignment at the Buffer/Cu(In,Ga)Se2 Thin‐Film Solar Cell Interface for CdS and GaOx

AbstractSputter‐deposited GaOx (i.e., oxygen‐deficient gallium oxide) films are evaluated as a potential replacement for the standard CdS buffer layers in Cu(In,Ga)Se2 (CIGSe) based thin‐film photovoltaics. The energy level alignment at the GaOx/CIGSe and CdS/CIGSe interfaces are compared by means of direct and inverse photoemission. For the GaOx/CIGSe a (0.04 ± 0.07) eV (i.e., a small spike‐like) conduction band offset (CBO) and a (−3.21 ± 0.19) eV (i.e., a large cliff‐like) valence band offset (VBO) are found, which suggests a nearly ideal charge‐selective contact. The derived GaOx band gap of (4.80 ± 0.25) eV confirms its utility as a highly transparent buffer layer. However, the GaOx (with x derived to be 1.1 ± 0.1) exhibits considerable (presumably) defect‐related occupied states above the valence band maximum. It is proposed that these states may increase charge carrier recombination and decrease open circuit voltage in respective devices; also explaining why solar cells with standard CdS buffer outperform devices with GaOx buffer, despite less ideal electronic interface properties (CBO: (−0.18 ± 0.07) eV, VBO: (−0.98 ± 0.15) eV) and the smaller CdS band gap of (2.35 ± 0.22) eV.

Optical and optoelectronic properties of gallium oxide films fabricated by the chemical vapour deposition method

The present work investigated the influence of growth time on the structural, optical, and optoelectronic properties of β-Ga2O3 films produced on Si substrates by the chemical vapour deposition method. The prepared films were characterized by X-ray diffraction, field-emission scanning electron microscope, and UV–Vis spectrophotometer. The films exhibited a mixed phase (β-α)-Ga2O3 crystal structure. The crystallite size ranged between 34.98 and 164.69 nm. The bandgap increased from 4.74 to 4.88 eV. The absorption and extinction coefficients were in the orders of 103 and 10−1, respectively. The refractive index, dispersive energy and single oscillator energy increased from 1.86 to 1.87, 19.24 to 28.64, and 8.36 to 9.54, respectively, with an increase of growth time. The oscillator strength, oscillator wavelength, third-order nonlinear optical susceptibility and dispersion of refractive index were in the orders of 10−4, 10−2, 10−10 and 10−9, respectively. The carrier concentration, optical conductivity, optical mobility, and optical resistivity were also evaluated. The real and imaginary dielectric constants, and plasmon frequency were also determined.

Influence of particle size distribution on dielectric, electrical, and microstructural properties of aerosol-deposited Ga2O3 film for advanced electronic device

Gallium oxide (Ga2O3) films have been the subject of recent scientific and technological research, owing to their outstanding characteristics. In this study, a rapid and efficient aerosol deposition (AD) process was utilized to produce Ga2O3 films. The effect of the particle size distribution (PSD) of the columnar or plate-like Ga2O3 starting powder on the dielectric, electrical, and microstructural properties of the films was also investigated. The dielectric constant and loss tangent of polycrystalline β-Ga2O3 films fabricated using AD with narrow PSD Ga2O3 powder were 10 and 6.7% at 10 kHz, respectively. In contrast, the films composed of a wide PSD powder exhibited a dielectric constant of 18 and a loss tangent of 3.6%. The leakage current densities of 1.77 × 10−5 and 6.63 × 10−7 A/cm2 at 5 V of the films using narrow and wide PSD powder were observed, respectively. In addition, the breakdown electric fields of the Ga2O3 films with narrow and wide PSD powder were 1.15 and 1.06 MV/cm, respectively. Qualitative and quantitative analyses of the surface and inner microstructure were conducted to elucidate the differences in film characteristics according to the PSD. Consequently, a wider PSD enables the production of relatively denser and flatter high-quality films owing to enhanced hammering and crush effects. These results suggest potential applications of Ga2O3 films fabricated using AD in various fields, such as capacitors, power semiconductors, and sensor devices.

GaSe/&lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; heterojunction based self-powered solar-blind ultraviolet photoelectric detector

UV photodetectors have the advantages of high sensitivity and fast response speed. As an ultra-wide bandgap semiconductor, gallium oxide (Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;) plays an extremely important role in detecting deep ultraviolet. It can form a typical type-II heterostructure with GaSe, promoting carrier separation and transport. In this work, Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; epitaxial films are grown on sapphire substrates by plasma-assisted chemical vapor deposition (PECVD). The GaSe films and GaSe/&lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; heterojunction photodetectors are grown on gallium oxide films by Bridgeman technology. The detector has a good response to deep ultraviolet light, the dark current of the device is only 1.83 pA at 8 V, and the photocurrent reaches 6.5 nA at 254 nm. The UVC/Visible (254 nm/600 nm) has a high rejection ratio of about 354. At very small light intensities, the responsivity and detection can reach 1.49 mA/W and 6.65 × 10&lt;sup&gt;11&lt;/sup&gt; Jones, respectively. At the same time, due to the photovoltaic effect formed by the space charge region at the junction interface, the detector exhibits self-powered supply performance at zero bias voltage, and the open-circuit voltage is 0.2 V. In addition, the detector has a very good sensitivity. The device can respond quickly, whether it is irradiated with different light intensities under constant voltage, or with different voltages under constant light intensity. It can respond within milliseconds under a bias voltage of 10 V. This work demonstrates the enormous potential of heterojunctions in photoelectric detection by analyzing the photophysical and interface physical issues involved in heterojunction photodetectors, and provides a possibility for detecting the deep ultraviolet of gallium oxide.

Influence of annealing pretreatment in different atmospheres on crystallization quality and UV photosensitivity of gallium oxide films.

Due to their high wavelength selectivity and strong anti-interference capability, solar-blind UV photodetectors hold broad and important application prospects in fields like flame detection, missile warnings, and secure communication. Research on solar-blind UV detectors for amorphous Ga2O3 is still in its early stages. The presence of intrinsic defects related to oxygen vacancies significantly affects the photodetection performance of amorphous Ga2O3 materials. This paper focuses on growing high quality amorphous Ga2O3 films on silicon substrates through atomic layer deposition. The study investigates the impact of annealing atmospheres on Ga2O3 films and designs a blind UV detector for Ga2O3. Characterization techniques including atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used for Ga2O3 film analysis. Ga2O3 films exhibit a clear transition from amorphous to polycrystalline after annealing, accompanied by a decrease in oxygen vacancy concentration from 21.26% to 6.54%. As a result, the response time of the annealed detector reduces from 9.32 s to 0.47 s at an external bias of 10 V. This work demonstrates that an appropriate annealing process can yield high-quality Ga2O3 films, and holds potential for advancing high-performance solar blind photodetector (SBPD) development.

Deposition and photoluminescence of zinc gallium oxide thin films with varied stoichiometry made by reactive magnetron co-sputtering

This paper reports on the deposition and photoluminescence of amorphous and crystalline thin films of zinc gallium oxide with Ga:Zn atomic ratio varied between 0.3 and 5.7. The films are prepared by reactive direct current magnetron co-sputtering from liquid/solid gallium/zinc targets onto fused quartz substrates; the temperature of the substrate is varied from room temperature (RT) to 800 °C. The sputtering process is effectively controlled by fixing the sputtering power of one of the targets and controlling the power of the other target by plasma optical emission spectroscopy. The method, in conjunction with oxygen flow adjustment, enables the production of near-stoichiometric films at any temperature used. The composition analysis suggests a few at% oxygen deficiency in the films. The resulting deposition rate is at least an order of magnitude higher compared to the commonly used radio-frequency sputtering from a ceramic ZnO:Ga2O3 target. Deposited onto unheated substrates, the films with Ga:Zn ≈ 2 are X-ray amorphous. Well-defined X-ray diffraction peaks of spinel ZnGa2O4 start to appear at a substrate temperature of 300 °C. The surface of the as-deposited films is dense and exhibits a fine-featured structure observed in electron microscopy images. Increasing the deposition temperature from RT to 800 °C eliminates defects and improves crystallinity, which for the films with Ga:Zn ratio close to 2 results in an increase in the optical band gap from 4.6 eV to 5.1 eV. Room temperature photoluminescence established the main peak at 3.1 eV (400 nm); a similar peak in Ga2O3 is ascribed to oxygen-vacancy related transitions. A prominent feature around 2.9 eV (428 nm) is attributed to self-activation center of the octahedral Ga-O groups in the spinel lattice of ZnGa2O4. It was found that photoluminescence from ZnGa2O4 depends significantly on the stoichiometric ratio between Ga and Zn and the deposition/annealing temperature.

Growth of polycrystalline gallium oxide films in nitrogen–oxygen–nitrogen, argon, and oxygen ambient

Growth of polycrystalline gallium oxide films in nitrogen–oxygen–nitrogen, argon, and oxygen ambient

Machine learning (ML)-assisted surface tension and oscillation-induced elastic modulus studies of oxide-coated liquid metal (LM) alloys

Pendant drops of oxide-coated high-surface tension fluids frequently produce perturbed shapes that impede interfacial studies. Eutectic gallium indium or Galinstan are high-surface tension fluids coated with a ∼5 nm gallium oxide (Ga2O3) film and falls under this fluid classification, also known as liquid metals (LMs). The recent emergence of LM-based applications often cannot proceed without analyzing interfacial energetics in different environments. While numerous techniques are available in the literature for interfacial studies- pendant droplet-based analyses are the simplest. However, the perturbed shape of the pendant drops due to the presence of surface oxide has been ignored frequently as a source of error. Also, exploratory investigations of surface oxide leveraging oscillatory pendant droplets have remained untapped. We address both challenges and present two contributing novelties- (a) by utilizing the machine learning (ML) technique, we predict the approximate surface tension value of perturbed pendant droplets, (ii) by leveraging the oscillation-induced bubble tensiometry method, we study the dynamic elastic modulus of the oxide-coated LM droplets. We have created our dataset from LM’s pendant drop shape parameters and trained different models for comparison. We have achieved >99% accuracy with all models and added versatility to work with other fluids. The best-performing model was leveraged further to predict the approximate values of the nonaxisymmetric LM droplets. Then, we analyzed LM’s elastic and viscous moduli in air, harnessing oscillation-induced pendant droplets, which provides complementary opportunities for interfacial studies alternative to expensive rheometers. We believe it will enable more fundamental studies of the oxide layer on LM, leveraging both symmetric and perturbed droplets. Our study broadens the materials science horizon, where researchers from ML and artificial intelligence domains can work synergistically to solve more complex problems related to surface science, interfacial studies, and other studies relevant to LM-based systems.

Performance Enhancement and In Situ Observation of Resistive Switching and Magnetic Modulation by a Tunable Two‐Level System of Mn Dopants in a‐Gallium Oxide‐based Memristor

AbstractPurely gallium oxide‐based memristors (GOMRs) show great potentials in resistive random‐access‐memory (RRAM) due to their chemical stability and resistive switching characteristics with Roff/Ron ratios up to 102; indeed, GOMRs with higher Roff/Ron ratios and more functionalities are more expected. In this study, ferromagnetic amorphous gallium oxide (a‐GMO) films with a tunable two‐level system of Mn dopants, i.e., Mn2+ and Mn3+ ions, are prepared by scalable polymer assisted deposition. The Pt/a‐GMO/Pt memristors show a high Roff/Ron ratio of 103, at least one order of magnitude higher than those of previously reported purely GOMRs, thanks to the abundant oxygen vacancies (VOs)‐induced low resistance state and Mn2+‐enhanced high resistance state. Meanwhile, magnetic modulation (MM) is realized electrically in the a‐GOMRs during the RS, through the tuning of bound magnetopolarons (BMPs) by bias voltage‐induced VOs variations, which may be useful for quaternary information coding. Notably, the transition between Mn3+ and Mn2+ions is observed in the GOMRs, which is closely related to the variations of VO concentration and BMP amount, providing an in situ tool to probe the VO‐induced RS and BMP‐dependent MM. The results give insights to Mn‐doped GOMRs and may be useful for design, fabrication, and testing of multifunctional high‐performance RRAMs.

2D Amorphous GaOX Gate Dielectric for β-Ga2O3 Metal-Insulator-Semiconductor Field-Effect Transistors

Beta gallium oxide (β-Ga2O3) is an n-type ultra-wide bandgap semiconductor material with a reported bandgap from 4.5 eV to 4.9 eV. β-Ga2O3 is a frontrunner in the research for next-generation power devices owing to its numerous merits including the wide range of donor doping concentrations, large bandgap, high theroretical value of critical electric field (~8 MV/cm) leading to substantial Baliga’s figure of merit of ~1900, and the low production cost for crystalline wafers. The last is enabled by the commercial development of several bulk growth techniques, namely, melt growth methods including Czochralski and edge-defined film-fed growth, and epitaxial growth. The metal-insulator-semiconductor field-effect transistor (MISFETs) is the most widely used device structure since it often requires less complicated fabrication process and offers better device scaling and faster switching speed than their counterparts such as junction field-effect transistors or bipolar junction transistors. Various dielectric materials, such as silicon dioxide, hafnium oxide, and aluminium oxide, have been explored for incorporation into β-Ga2O3 MISFETs. However, many of the dielectrics require high-temperature and/or high-vacuum processes during fabrication. Recent studies have reported on the self-limiting formation of native oxide film on the surface of liquid gallium at room temperature and the application of the oxide film as a passivation or a dielectric layer in a nano-scale device. In this study, two-dimensional (2D) amorphous gallium oxide (a-Ga2O3) film is fabricated through the liquid gallium squeezing technique and is integrated with a β-Ga2O3 field-effect transistor (FET) to demonstrate an a-Ga2O3/β-Ga2O3 MISFET.In this work, β-Ga2O3 nano-flakes were obtained through mechanical exfoliation and were dry-transferred onto Si/SiO2 substrates. Electron-beam lithography and electron-beam evaporation were performed to define and deposit Ti/Au electrodes, respectively, where rapid thermal annealing was performed afterward to form Ohmic source and drain contacts. Polypropylene carbonate (PPC) solution was spin-coated and baked on a polydimethylsiloxane (PDMS) film, placed on a glass slide for mechanical support, to form a uniform PPC layer on the PDMS film. A liquid gallium droplet was placed on the PPC/PDMS film and was squeezed with a cleaned glass slide to form a uniform 2D a-Ga2O3 layer. The fabricated a-Ga2O3 layer was dry-transferred onto a β-Ga2O3 FET during which temperature of 90 °C was applied to the sample chuck to completely release the PPC layer with the a-Ga2O3 layer from the PDMS layer. The resulting a-Ga2O3/β-Ga2O3 FET was submerged in acetone to remove the PPC layer. The above dry-transfer process of the a-Ga2O3 layer was conducted twice to form double-layered a-Ga2O3 on the β-Ga2O3 FET, before performing electron-beam lithography and electron-beam evaporation to respectively define and deposit the Ni/Au top-gate electrode.The electrical properties of the fabricated device is characterized as a Ni/a-Ga2O3/β-Ga2O3 heterojunction and an a-Ga2O3/β-Ga2O3 MISFET at temperatures of 25 °C, 150 °C, and 250 °C. The Ni/a-Ga2O3/β-Ga2O3 heterojunction of the device shows a clear rectification characteristic with a wider operating voltage compared to those of standard Ni/β-Ga2O3 devices in literatures. The double-layered a-Ga2O3 The a-Ga2O3/β-Ga2O3 MISFET exhibits normally-on n-type conductivity with stable operation at temperatures from 25 °C to 250 °C, where the obtained on/off current ratio and mobility range from 5.3×108 to 4.8×107 and 4.7 cm2/V·s to 6.9 cm2/V·s, respectively. The subthreshold swing and the threshold voltage of the a-Ga2O3/β-Ga2O3 MISFET showed increases and negative shifts at higher temperatures, respectively. This work demonstrates the facile fabrication process of the a-Ga2O3/β-Ga2O3 MISFET and its high-temperature stability through the integration of the 2D amorphous Ga2O3 gate dielectrics with a β-Ga2O3 semiconductor.

Influence of White Light on the Photoelectric Characteristics of UV Detectors Based on β-Ga2O3

In this report, we consider the effect of radiation with a radiation energy below the β-Ga2O3 band-gap on the photoelectric characteristics of ultraviolet (UV) radiation detectors based on gallium oxide thin films. The gallium oxide film was deposited by the radio frequency magnetron sputtering. Interdigital Ti/V electrodes were formed with an inter electrode distance d = 30 μm. The structures exhibit high value of photocurrent under irradiation with wavelength of λ = 254 nm and intensity of 780 μW/cm2. The detectors exhibit persistent photoconductivity after exposure to UV radiation. The presence of persistent conductivity is explained by the high concentration of traps in the Ga2O3 film and their recharging under UV irradiation. Radiation with an energy quantum below the the β-Ga2O3 band-gap changes the charge state of trap centers in a gallium oxide film. This effect leads to an increase in photocurrent under UV exposure and increases the stability of detectors.

Chemical reaction-mass transport model of Ga2O3 grown by TEGa in MOCVD and an intelligent system

Gallium oxide (Ga2O3) is rationally expected to have a wide range of applications prospects in power electronics, solar-blind UV detectors, gas detectors, and other fields. Metal-organic chemical vapor deposition (MOCVD) is a key technology for achieving high-quality and large-scale film growth, but with complex fluid fields, temperature fields, component distribution, and chemical reaction processes, the process is akin to a black box. In this study, the computational fluid dynamics (CFD) approach and a complete reaction mechanism were used to model the chemical reaction and mass transport for gallium oxide film growth based on a vertical rotating disc reactor (RDR) MOCVD system. The effect of temperature on film growth was explored and analyzed. It was found that the growth temperature can be divided into four regions, respectively controlled by thermal flow field, reaction rate, component transport, and parasitic reaction, and there is a competitive relationship between them. In the component transport region, the influence of different process parameters such as pressure, flow rate, and rotational speed on the growth was investigated. The regulation of film uniformity is achieved by the coupled regulation of 5 pairs of MO source inlets and multiple process parameters. Combined with artificial intelligence techniques, an intelligent system for realizing flow field visualization, growth result prediction, process parameter optimization, and abnormal result tracking was proposed for the first time. It can provide systematic guidance for film growth.

Synthesis of porous γ-gallium oxide films using refrigerator aging oxidation from gallium nanoparticles

Porous gallium oxide films were tried to synthesize at low temperatures. Ga nanoparticle dispersions were synthesized using ultrasound irradiation in 2-propanol and two films methods were considered. In the case of the spray coating of Ga nanoparticle dispersions and treatment with hydrazine vapor, Ga films were obtained. In the case of depositing Ga nanoparticles on a cover glass and aging them in hydrazine solution at a refrigerator temperature, porous γ-Ga2O3 film was synthesized. This new process of low-temperature aging in a refrigerator using hydrazine solution allows synthesizing porous γ-Ga2O3 film. Generally, the synthesis of oxide ceramics requires high-temperature processing, but this method allows oxidation at low temperatures, such as refrigerator temperatures, making it an energy-efficient process.