Wenrui Zhang

The electrical properties of Si-doped β-Ga2O3 homoepitaxial films are governed by the interaction between Si donor activation and native point defects formed during metal−organic chemical vapor deposition (MOCVD) growth. Although growth pressure directly affects precursor transport, boundary-layer evolution, gas-phase reactions, and surface kinetics, its role in regulating defect-mediated carrier transport remains insufficiently understood. Here, we systematically investigate the effect of the growth pressure on the structural, electrical, and defect properties of MOCVD-grown Si-doped β-Ga2O3 (100) homoepitaxial films. The film grown at 40 mbar exhibits a carrier concentration of 4.7 × 1017 cm−3 and a Hall mobility of 120.0 cm2/(V·s). As the growth pressure increases from 50 mbar to 80 mbar, the β-Ga2O3 films show a much lower dopant activation efficiency and lower Hall mobility. Combined temperature-dependent Hall, cathodoluminescence, and X-ray photoelectron spectroscopy analyses indicate that elevated pressure reduces the concentration of electrically active SiGa(I) donors, which dominates the decrease in carrier concentration, while increasing vacancy-related defects, including gallium-oxygen divacancy (VGa-VO) complexes and oxygen vacancy (VO)-related oxygen-deficient environments, which act as scattering centers and lower the mobility. Lateral MOSFETs fabricated on the film grown at 40 mbar achieve a drain on/off ratio above 109, a specific on-resistance of 169.8 mΩ·cm2, and a breakdown voltage exceeding 3 kV. This work reveals how growth pressure modulates the formation of native defects and defect-mediated carrier transport in Si-doped β-Ga2O3 homoepitaxy, providing mechanistic insight into developing high-mobility channel layers for β-Ga2O3 power devices.

Gallium oxide (Ga2O3) is an emerging ultrawide bandgap semiconductor for high-power electronics and solar-blind optoelectronics. Here we demonstrate an atomic-scale strain relaxation method to achieve a complete α-to-β Ga2O3 phase transition within the initial nucleation stage, enabling a heteroepitaxial growth regime of single-crystalline β-Ga2O3 (010) films. An Ar+ bombardment strategy is used to create periodic strain relaxation sites that relieve the compressive strain in the metastable α-Ga2O3 interlayer and facilitate the phase transition, as revealed by a combination of X-ray diffraction, atomic-force microscopy, atomic-resolution scanning transmission electron microscopy, and geometric phase analysis. The heteroepitaxial Sn-doped β-Ga2O3 (010) films with distinct donor activation behavior are established on m-plane sapphire, and a lateral Schottky barrier diode with a high reverse breakdown voltage of 1590 V is achieved. This study provides critical insights into atom-scale strain engineering and confined epitaxial growth for developing high-quality β-Ga2O3 films on cost-effective substrates for advanced electronic devices.

Solar-blind ultraviolet (UV) photodetection on silicon platforms is an important step toward practical optoelectronic integration. Here, we demonstrate a bottom-gate ZnGa2O4 metal-oxide-semiconductor field-effect transistor (MOSFET) solar-blind UV photodetector on a Si substrate with a Si3N4 gate dielectric. The device exhibits n-channel enhancement-mode operation with an on/off current ratio of ∼108 and a picoampere-level off-state current. Under solar-blind UV illumination, the phototransistor achieves a peak responsivity of 1.09 × 103 A/W, a detectivity of 1.74 × 1013 Jones, a UV-to-visible rejection ratio of 2.6 × 105, and rise/decay times of 22.7/19.2 ms. The photo-induced shift in the capacitance–voltage characteristics suggests the participation of charge trapping at the Si3N4/ZnGa2O4 interface, while cathodoluminescence and electrical analyses identify compensating zinc vacancy (VZn) acceptor defects coexisting with Ga-on-Zn (GaZn) antisite donors within the ZnGa2O4 channel. These trap states sustain two parallel gain pathways within the MOSFET architecture: vertical threshold-voltage modulation amplified through the subthreshold characteristic, and lateral photoconductive gain arising from carrier lifetime extension via hole capture by VZn acceptor defects. By distributing the total gain across two amplification channels rather than relying on prolonged carrier lifetime alone, this architecture offers a route to balanced high-gain and fast-response solar-blind UV detection on Si platforms compatible with CMOS technology.

Recessed‐gate enhancement‐mode (E‐mode) β‐Ga ₂ O ₃ MOSFETs are demonstrated using a damage‐mitigated process combining plasma etching and a two‐step wet chemical repair. The repair treatment reduces surface roughness of the etched surface from 4.65 nm to 0.52 nm without affecting the recess channel depth. The fabricated (MOSFET) Metal‐oxide‐semiconductor field‐effect transistors exhibits a threshold voltage of 9.6 V, a saturation drain‐current density of 54.7 mA/mm, a low on‐resistance of 151.7 Ω·mm, and a peak transconductance exceeding 8 mS/mm. A high‐quality restored Al ₂ O ₃ /β‐Ga ₂ O ₃ interface is suggested from a subthreshold swing of 258.6 mV/dec, an interface trap density of 1.9 × 10 ¹² cm ⁻² ·eV ⁻¹ , and an on/off ratio above 10 ⁹ . Furthermore, the E‐mode MOSFET is monolithically integrated with a depletion‐mode (D‐mode) β‐Ga ₂ O ₃ MOSFET to obtain an E/D NMOS inverter, which exhibits a voltage gain of 4.6 and balanced low/high noise margins of 5.5 V/7.4 V. These findings establish a viable route toward high‐performance β‐Ga ₂ O ₃ logic circuits.

Diamond based deep-ultraviolet photodetectors exhibit significant potential applications in communications, sensing and imaging. However, the challenge of n-type doping restricts the fabrication of diamond pn structural photodetectors. In this work, a photodetector based on n-ɛ-Ga2O3/p-diamond heterojunction was fabricated by depositing n-type ɛ-Ga2O3 on p-type diamond substrate via pulsed laser deposition (PLD). X-ray photoelectron spectroscopy (XPS) analysis indicated the ɛ-Ga2O3/diamond heterojunction possesses a Type II band structure, with valence and conduction band offsets of approximately 2.23 eV and 3.10 eV, respectively. The fabricated detector exhibits an ultra-low dark current of 1.47×10-12 A and a high photo-to-dark current ratio (PDCR) of 106. The detector also demonstrated excellent spectral selectivity in the deep-ultraviolet wavelength region. Moreover, the detector exhibits the self-power ability when illuminated by DUV light due to the formation of the hetero p-n junction. This study demonstrates the feasibility of integrating Ga2O3 with diamond and paves the way for the design and analyses of future deep-ultraviolet photodetectors based on Ga2O3/diamond heterojunction.

We report a lateral β-Ga₂O₃ MOSFET incorporating a simple Si₃N₄ terminal structure for electric-field management. The main contribution of this work is the demonstration that this process-compatible terminal design can enhance the breakdown performance while preserving the forward conduction characteristics of the device. The epitaxial layer exhibits high crystalline quality, a smooth surface morphology, and favorable carrier transport properties. With the Si₃N₄ terminal structure, the device achieves a breakdown voltage exceeding 3 kV, and the average breakdown field is increased from 0.85 MV/cm to 1.63 MV/cm. Meanwhile, the forward conduction characteristics are well maintained. Electric-field simulations further reveal that the Si₃N₄ terminal structure effectively mitigates electric-field crowding at the gate edge, accounting for the improved breakdown behavior. These results demonstrate that the Si₃N₄-based terminal design provides a simple and effective strategy for simultaneously improving breakdown performance and maintaining forward conduction characteristics in lateral β-Ga₂O₃ MOSFETs.