In this study, the influence of HfO₂ interlayer thickness on the performance of heteroepitaxial α-Ga₂O₃ layer-based metal–insulator–semiconductor–insulator–metal (MISIM) ultraviolet photodetectors is examined. A thin HfO₂ interlayer enhances the interface quality and reduces the density of interface traps, thereby improving the performance of UVC photodetectors. The fabricated device with a 1 nm HfO₂ interlayer exhibited a significantly reduced dark current and higher photocurrent than a conventional metal–semiconductor–metal (MSM). Specifically, the 1 nm HfO₂ MISIM device demonstrated a photocurrent of 2.3 μA and a dark current of 6.61 pA at 20 V, whereas the MSM device exhibited a photocurrent of 1.1 μA and a dark current of 73.3 pA. Furthermore, the photodetector performance was comprehensively evaluated in terms of responsivity, response speed, and high-temperature operation. These results suggest that the proposed ultra-thin HfO₂ interlayer is an effective strategy for enhancing the performance of α-Ga₂O₃-based UVC photodetectors by simultaneously suppressing dark currents and increasing photocurrents and ultimately demonstrate its potential for stable operation under extreme environmental conditions.

A novel doping technique with an initiated chemical vapor deposition (iCVD) process is applied to fabricate aluminum (Al)-doped zinc oxide (ZnO) channel thin-film ultraviolet (UV) phototransistor (PT). The iCVD doping technique can successfully introduce Al throughout the ZnO channel without any surface damage. The sub-bandgap states mainly due to oxygen vacancy (V $_{\text{O}}$ ) defects in the ZnO channel are effectively suppressed by Al doping; the subthreshold swing (SS) of the PT has been reduced by more than half to 168 mV/dec and under negative gate bias illumination stress, the threshold voltage shift is reduced by about half to $-$ 2.03 V, which improves the reliability. For the UV detection, the Al-doped ZnO PT exhibits a high responsivity of 358.93 A $\cdot$ W $^{-\text{1}}$ , an ultrahigh UV-to-visible rejection ratio of 4.81 $\times$ 10 $^{\text{6}}$ , a high detectivity ( D $^\ast)$ of 1.68 $\times$ 10 $^{\text{15}}$ Jones, a low noise equivalent power (NEP) of 2.98 $\times$ 10 $^{-\text{18}}$ W $\cdot$ Hz $^{-\text{1}}$ , and fast switching performance. The developed Al-doped ZnO PT can be used in low-cost and high-performed UV detection for various applications.

We demonstrate a Sn-doped monoclinic gallium oxide (β-Ga₂O₃)-based deep ultraviolet (DUV) phototransistor with high area coverage and manufacturing efficiency. The threshold voltage (V_T) switches between negative and positive depending on the β-Ga₂O₃ channel thickness and doping concentration. Channel depletion and Ga diffusion during manufacturing significantly influence device characteristics, as validated through computer-aided design (TCAD) simulations, which agree with the experimental results. We achieved enhancement-mode (e-mode) operation in <10 nm-thick channels, enabling a zero V_G to achieve a low dark current (1.84 pA) in a fully depleted equilibrium. Quantum confinement in thin β-Ga₂O₃ layers enhances UV detection (down to 210 nm) by widening the band gap. Compared with bulk materials, dimensionally constrained optical absorption reduces electron–phonon interactions and phonon scattering, leading to faster optical responses. Decreasing β-Ga₂O₃ channel thickness reduces V_T and V_G, enhancing power efficiency, dark current, and the photo-to-dark current ratio under dark and illuminated conditions. These results can guide the fabrication of tailored Ga₂O₃-based DUV phototransistors.

It is demonstrated that interface engineering in ZnO-based ultraviolet (UV) photodetectors (PDs) using an asymmetric Al₂O₃ interlayer can significantly enhance PD performance. The Al₂O₃ layer deposited by atomic layer deposition (ALD) only at the cathode/ZnO interface extends the electron tunneling distance and passivates oxygen vacancy ( ${V}_{\text{O}}$ )-related traps on the ZnO surface. This effectively suppresses the dark current ( ${I}_{\text {dark}}$ ), while the photocurrent ( ${I}_{\text {photo}}$ ) remains high due to the absence of the Al₂O₃ layer in the anode region. An asymmetric ZnO metal–insulator–semiconductor–metal (MISM) PD with an optimized Al₂O₃ layer thickness of 4 nm exhibits a high photo-to-dark current ratio (PDCR) of $2.31\times 10^{{5}}$ , a high specific detectivity of $7.80\times 10^{{14}}$ Jones, a rapid decay time of 0.12 s, and excellent performance in harsh environments.

α-Ga2O3, a wide-bandgap semiconductor, has emerged as a promising material for diverse applications. This study presents a high-performance deep-ultraviolet (DUV) photodetector (PD) based on a hetero-epitaxial α-Ga2O3 thin film with reduced defects. The 200-nm-thick α-Ga2O3 thin film is directly grown on a sapphire substrate without a buffer layer using hydride vapor phase epitaxy. The film exhibited strong absorption exceeding 80% in the DUV region below 280 nm and excellent solar-blind characteristics. Post-growth rapid thermal annealing (RTA) in an oxygen atmosphere reduces the oxygen vacancy concentration from 17% to 12%, effectively eliminating defects and enhancing charge transport and collection. The device subjected to RTA for 5 min exhibits a responsivity of 2.03 A W−1, a detectivity of 6.95 × 1013 Jones, an external quantum efficiency of 1095%, and rise and decay times of 2.352 and 0.266 s, respectively. These values represent significant improvements over those of the unannealed device (1.08 A W−1, 3.32 × 1013 Jones, 583%, and 3.263 and 0.484 s, respectively). These results demonstrate that RTA offers a simple yet effective means of enhancing device performance by controlling defects without altering the device structure, highlighting α-Ga2O3 as a cost-effective platform for high-performance DUV PDs.