Solar-blind photodetectors have received increasing attention due to their widely applications in military and civil aspects. However, most of the photodetectors exhibit low detection ability for weak ultraviolet light signal, and the forewarning of weak ultraviolet radiation is important for the immune system of humans. Herein, the self-powered photodetector based on $\beta $ -Ga ₂ O ₃ /NiO heterojunction with an ultralow dark current (1.09 nA at −15 V) has been fabricated, and the synthesized platinum (Pt) nanoparticles (NPs) are used for surface modification of the device. The obtained devices with Pt NPs exhibit a large ${I}_{\text {photo}}/{I}_{\text {dark}}$ ratio of 9153, an excellent detectivity of $4.2\times 10^{9}$ Jones, an ultrahigh linear dynamic range of 79 dB, and a high responsivity of 4.27 mA/W, with respective enhancements over 4476%, 2220%, 71.7%, and 2442% compared to the pristine device, respectively. These results indicated that the device has the excellent ability for weak ultraviolet light signal detection, and the enhanced performance can be attributed to the Pt NPs, which can remarkably enhance the generation of photogenerated carriers via the formation of the local electric field and the local surface plasmon resonance effect. The experiment provides an effective method for fabricating high-performance solar-blind photodetector.

As a promising ultra-wide bandgap (UWBG) semiconductor, gallium oxide (Ga₂O₃) has recently aroused increasing attention in the area for high-power electronics, power switch for radio frequency (RF) operation, and solar blind UV detectors. The β-phase of Ga₂O₃ is deemed as a potential candidate for next generation high-power electronics due to its high theoretical breakdown electric field (8 MV cm⁻¹), UWBG (4.8 eV), and large Baliga’s figure of merit. Owing to the intensive research efforts across the world since 2013, gallium oxide transistors recently make rapid advances in device design and performance. Until now, high quality large-size bulk Ga₂O₃ and n-type epi products are successively coming onto the market, as well as there are gratifying progress worldwide to develop more complex epi structures, including β-(Al _x Ga_1−x )₂O₃/Ga₂O₃, β-(In _x Ga_1−x )₂O₃/Ga₂O₃, n-Ga₂O₃/p-NiO, β-Ga₂O₃/4H-SiC heterostructures et al. In this paper, the basic physical properties of Ga₂O₃, and the recent research process of Ga₂O₃ based transistors field-effect transistor (FET) for high-power electronics and RF are introduced. Furthermore, various state-of-the-art structures and process used in Ga₂O₃ based FETs have been summarized and compared, including planar/vertical metal-oxide-semiconductor field-effect transistor (MOSFET), trench MOSFET, FinFET, modulation-doped FET or called it high electron mobility transistors with two-dimensional electron gas channel, SOI MOSFET, thus the potential of Ga₂O₃ FETs is preliminary revealed. Finally, the prospect of the Ga₂O₃ based FET for high-power and RF application will be also analyzed.

As the p-type doping β-Ga ₂ O ₃ is absent up to now, metal gate (MG) stacks with high work functions are expected to benefit the fabrication of normally-OFF β-Ga ₂ O ₃ transistors. In this article, the electrical characteristics of β-Ga ₂ O ₃ metal-electrode-gated metal-oxide- semiconductor (MOS) devices with Al-rich HfAlO dielectrics and different MG stacks (Ni, Au, Pt, and Ti) are evaluated. The interface state density (Dit) of HfAlO/β-Ga ₂ O ₃ interface is characterized based on the frequency-dependent capacitance-voltage (C-V) and photo-assisted deep ultraviolet (DUV) C-V measurements. An average Dit of 4.45 × 1011 eV ^-1 cm ^-2 is extracted from the photo-assisted (deep UV) C-V measurement, while a large amount of border traps, negative fixed charges, and deep traps is also induced at the oxide layer and/or HfAlO/β-Ga ₂ O ₃ interface. Then, this article investigates the evaluations of Ti, Ni, Au, and Pt as candidate MGs for β-Ga ₂ O ₃ MOS using Al-rich HfAlO as gate dielectric. The obvious flat-band voltage (VFB) shift and gate leakage variation are observed in β-Ga ₂ O ₃ capacitors with different MG solutions, indicating that HfAlO dielectric combined with Ni, Au, and Pt MGs is promising to facilitate some beneficial modifications of normally-OFF β-Ga ₂ O ₃ transistors, while Ti electrode is more suitable for normally-ON β-Ga ₂ O ₃ transistors. This article provides an additional practical guideline for choosing the appropriate MG stacks and potential gate dielectric to the development of normally-OFF Ga ₂ O ₃ transistors.

In this article, the planar $\beta $ -Ga₂O₃ junctionless transistors with/without unintentional doping (UID) buffer layer are numerically investigated. It was found that the double-layer Ga₂O₃ MOSFETs (epilayer/buffer layer) show a trade-off between threshold voltage ( ${V}_{\text {th}}$ ) and device reliability (resulting from anomalous Fe out-diffusion), as a function of the thickness ( ${T}_{\text {buf}}$ ) and carrier concentrations ( ${N}_{\text {buf}}$ ) of $\beta $ -Ga₂O₃ buffer layer. The simulation results show that an adequate buffer layer (200 nm $ < {T}_{\text {buf}} < {500}$ nm, ${N}_{\text {buf}} < {5}\times {10}^{{14}}$ cm⁻³) is beneficial to the pinch-off characteristic of $\beta $ -Ga₂O₃ planar MOSFETs. A novel triple-layer MOSFET (introducing a low-doped $\beta $ -Ga₂O₃ surface layer above the epilayer) is subsequently proposed and demonstrated to be an easy pathway to modulate ${V}_{\text {th}}$ by adjusting the thickness and doping concentration of surface layer. In addition, the effect of the lateral extension N⁺ region is also discussed. As a result, the triple-layer $\beta $ -Ga₂O₃ MOSFET with an optimized dimension can achieve positive enhancement-mode and better device performance: breakdown voltage ( ${V}_{\text {br}}$ ) and power figures of merit (P-FOM) are improved by 173.71% and 65.37%, respectively, while specific ON-resistance is increased by 391.35%.

Silicon Carbide (SiC) Ultraviolet (UV) phototransistors with bidirectional bias response were fabricated and analyzed in this letter. The results showed that the fabricated UV phototransistor exhibited stable photoelectric response characteristics and transistor characteristics under both forward and reverse voltages, owing to the structure design of the epi-layers, while the mechanism of the bidirectional response was also studied. The difference in photocurrent under different bias voltages and wavelengths of UV illumination were mainly due to the variation of the absorption coefficient with wavelength and the change in the width of the space charge regions, which ultimately led to a difference in the number of photo-generated carriers. The time response characteristics of the detector showed that there were time delays when the detector was turned on and turned off, which was caused by the photo minority carriers in the depletion layer of the base-collector junction.