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Abstract β-Ga2O3 is a promising ultrawide-bandgap semiconductor for high-power electronics; however, the realization of thick, low-defect drift layers at high growth rates remains challenging. In this work, metalorganic chemical vapor deposition (MOCVD) growth of (011) β-Ga2O3 drift layers on (011) β-Ga2O3 substrates is optimized using a far-injection showerhead reactor with trimethylgallium (TMGa) and O2 precursors. The effects of chemical pre-treatment, in situ oxygen annealing, wafer carrier rotation, and pulse-flow (PF) β-Ga2O3 interlayers are systematically investigated to correlate growth conditions with defect density. Chemical treatment B [18% HCl (10 min) + deionized (DI) water (10 min) + 49% HF (30 min)], combined with 1 h of in situ annealing at 900 °C, minimizes defect density under the selected growth conditions. Incorporation of a single PF1 interlayer (∼30 nm thick) further suppresses defect formation, reducing the defect density by more than one order of magnitude. Atomic force microscopy (AFM) reveals sub-nanometer root mean square (RMS) roughness and step-flow morphology for ∼11 μm thick films. High-resolution X-ray diffraction (XRD) rocking curves confirm the preserved crystalline quality. Field-plated Schottky barrier diodes (SBDs) fabricated on optimized films exhibit excellent forward conduction, low reverse leakage, and improved breakdown performance, highlighting the importance of defect control for high-performance vertical power devices. 

Abstract In this study, we demonstrate a novel approach for synthesizing free‐standing and transferable polycrystalline diamond membranes (PCDm) to overcome these constraints, thus enabling a much wider spectrum of applications. Two types of PCDm cantilevers —Top‐Surface‐Up (TSU) and Bottom‐Surface‐Up (BSU) are fabricated, each with two different sets of dimensions: 150 µm (width) × 1200 µm (length) and 300 µm (width) × 2000 µm (length). Their mechanical and electrical properties are systematically investigated. Atomic Force Microscopy (AFM) analysis revealed that TSU‐PCDm has a higher elastic modulus than BSU‐PCDm, attributed to differences in grain size and defect distribution. Despite these differences, all PCDms in our work exhibit consistently high modulus values with minimal mechanical degradation across various cantilever geometries. Bandgap measurements using X‐ray Photoelectron Spectroscopy (XPS) and UV–vis absorption spectroscopy indicated a lower bandgap for TSU‐PCDm due to boron incorporation, while BSU‐PCDm exhibited a higher bandgap due to increased hydrogen content. Electrical characterization showed that the sheet resistance of TSU‐PCDm decreases under strain, whereas BSU‐PCDm maintains stable resistance. These findings unveil the material properties of PCDm and their potential usage for myriad diamond‐based electronic applications. 

Abstract This letter reports high performanceβ- (Al_xGa_1−x)₂O₃/Ga₂O₃Heterostructure FET (HFET) with an improved regrowth process and successful Al₂O₃passivation. Highly scaled I shaped gates (100–200 nm L_G) have been fabricated with degenerately doped (N++) source/drain contact regrown by ozone molecular beam epitaxy (MBE). Aiming to address the limitations observed in previously reported devices, this work incorporates a low-power BCl₃/Ar and SF₆/Ar plasma etching process to remove the AlGaO barrier layer and Ga₂O₃layer respectively before regrowth. Additionally, the surface was cleaned, and vacuum annealing was carried out before MBE regrowth to reduce any interface resistance between highly doped regrowth N++ and 2DEG layer. These meticulously designed fabrication steps enabled us to achieve the high DC current 0.5 A mm⁻¹at 5 V drain bias with 6.1 Ω.mm on resistance (R_ON) at V_GS = 3 V, peak transconductance (g_m) of 110 mS mm⁻¹at room temperature (V_DS = 15 V) and around 0.8 A mm⁻¹(V_DS = 5 V) peak I_ONat low temperature (100 K). The current gain cut-off frequency (f_T) of 32 GHz and peak power gain cut-off frequency (f_MAX) of 65 GHz were extracted from radiofrequency (RF) measurements. The reported f_MAXis one of the highest for Ga₂O₃based RF devices to the best of the authors’ knowledge. The f_T.L_Gproduct was estimated to be 6.1 GHz-μm for 191 nm L_Gand 32 GHz f_T, which is one of the highest reported among Ga₂O₃devices. After passivating the device with thicker Al₂O₃, the device shows no current collapse demonstrating first time successful traps passivation with Al₂O₃forβ-Ga₂O₃devices. 

Abstract (Al_xGa_1–x)₂O₃ is an ultrawide‐bandgap semiconductor with a high critical electric field for next‐generation high‐power transistors and deep‐ultraviolet photodetectors. While (010)‐(Al_xGa_1–x)₂O₃ films have been studied, the recent availability of (100), (01)‐Ga₂O₃ substrates have developed interest in (100), (01)‐(Al_xGa_1–x)₂O₃ films. In this work, an investigation of microscopic and spectroscopic characteristics of (100), (01), (010)–(Al_xGa_1–x)₂O₃ films is conducted. A combination of scanning transmission electron microscopy, atom probe tomography (APT), and first‐principle calculations (DFT) is performed. The findings reveal consistent in‐plane chemical homogeneity in lower aluminum content (x = 0.2) films. However, higher aluminum content (x = 0.5), showed inhomogeneity in (100), (010)–(Al_xGa_1–x)₂O₃ films attributed to their spectroscopic properties. The study expanded APT's capabilities to determine Ga─O and Al─O bond lengths by mapping their ion‐pair separations in detector space. The change in ion‐pair separations is consistent with varying orientations, irrespective of aluminum content. DFT also demonstrated a similar trend, concluding that Ga─O and Al─O bonding energy has an inverse relationship with their bond length as crystallographic orientations vary. This systematic study of growth orientation dependence of (Al_xGa_1–x)₂O₃ films’ microscopic and spectroscopic properties will guide the development of new (100) and (01)‐(Al_xGa_1–x)₂O₃ along with existing (010)–(Al_xGa_1–x)₂O₃ films. 

β-Ga2O3 and its alloys are promising for next-generation high-power electronic devices, but realizing high-quality thick epitaxial layers with smooth morphology at high growth rates remains a major challenge. In this study, we systematically investigated the metalorganic chemical vapor deposition (MOCVD) growth of β-Ga2O3 on edge-defined film-fed growth (EFG, Sn doped) and vertical bridgman (VB, Fe doped) (001) β-Ga2O3 substrates. (001) β-Ga2O3 films grown on both substrates show similar cracking issue. Films grown on EFG substrates show lower atomic force microscopy roughness as compared to those grown on VB substrates. X-ray diffraction (XRD) measurements indicate lower crystalline quality in films grown on VB substrates compared to films grown on EFG substrates. XRD rocking curves also illustrate that films grown on VB substrates have higher structural anisotropy. From cross-sectional scanning transmission electron microscopy (STEM) imaging, surface reconstruction occurred at the growth interface for both EFG and VB substrates. MOCVD growth of β-(Al0.0625Ga0.9375)2O3 on (001) β-Ga2O3 substrates indicate crack-free layers can be grown up to 6 μm at a growth rate of 4.5 μm/h. STEM atomic-scale analysis revealed a uniform Al-distributed interfacial layer at the growth interface followed with an Al-segregated region aligning along the (1¯01) plane. Electrical measurements revealed low mobility in thick (001) AlGaO layers which is due to crystal rotation and Al segregation. These results provide understanding of MOCVD growth of (001) β-Ga2O3 and (001) β-(AlxGa1−x)2O3 films at fast growth rates and insights into the interplay of growth chemistry, substrate selection, and alloy incorporation. 

This study demonstrates a substantial enhancement of breakdown voltage in β-Ga2O3 Schottky barrier diodes through an approach that combines fast neutron irradiation with controlled post-irradiation electro-thermal annealing. Devices irradiated with 1 MeV neutrons at a high fluence of 1 × 1015 n/cm2 initially exhibited substantial degradation, including a drastic reduction in on-current and an increase in on-resistance. Electro-thermal testing, conducted through simultaneous current–voltage measurements while heating the devices up to 250 °C, resulted in significant recovery. After four cycles of electro-thermal testing, the devices demonstrated significant improvements in performance, with a substantial recovery of on-current and a reduction in on-resistance compared to the post-radiation condition, approaching pre-radiation levels. Most recovery occurred during the first two cycles, with diminishing improvements thereafter, indicating that thermally responsive radiation-induced traps were largely mitigated early in the process. Capacitance–voltage measurements revealed a substantial reduction in net carrier concentration, decreasing from 3.2 × 1016 cm−3 pre-radiation to 5.5 × 1015 cm−3 after the first electro-thermal testing cycle, indicating an over 82% reduction. Following the third cycle, the carrier concentration partially recovered to 9.9 × 1015 cm−3, reflecting a carrier removal rate of ∼22 cm−1. The breakdown voltage (Vbr) exhibited a remarkable enhancement, increasing from approximately 300 V to 1.28 kV (a ∼325% improvement) after the first electro-thermal testing, which can be attributed to the reduction in net carrier concentration by compensating radiation-induced traps. Subsequent testing reduced Vbr slightly to 940 V due to partial recovery of carrier concentration, but it remained significantly higher than pre-radiation levels. These findings demonstrate the potential of combining neutron irradiation with electro-thermal annealing to significantly enhance the voltage-blocking capability of β-Ga2O3 power devices, making them strong candidates for high-power applications in radiation-intense environments. 

In this work, p-type NiO thin films were grown on (010) β-Ga2O3 substrates via metal–organic chemical vapor deposition (MOCVD). The growth conditions, including Ni(dmamb)2 (Ni precursor) molar flow rate, oxygen flow rate, and growth temperature, were systematically tuned to achieve p-type NiO thin films. With a relatively high O2 flow rate of 10 000 sccm, the grown NiO film exhibited smooth surface morphologies with a root mean square roughness value of 2.39 nm. The measured hole concentration ranged from 1 × 1016 to 4.5 × 1016 cm−3, with room-temperature mobility varying between 3 and 1.7 cm2/V s. Cross-sectional scanning transmission electron microscopy imaging and analysis revealed a NiGa2O4 interfacial layer formed between the p-type NiO thin film and β-Ga2O3 substrate, due to Ni diffusion. Given the challenges of achieving p-type conductivity in β-Ga2O3, NiO has emerged as a potential alternative material. Furthermore, in situ MOCVD grown NiO/β-Ga2O3 heterojunction was used to fabricate PN diodes with two different diameters: 100 and 200 μm. This study represents the first demonstration of all-MOCVD growth of p-NiO/β-Ga2O3 PN diodes on (010) Sn-doped β-Ga2O3 substrates. Compared to radio frequency sputtering and atomic layer deposition of p-NiO, MOCVD allows the continuous growth of p-NiO on top of Ga2O3, which can potentially suppress interface defects and impurity contamination. The breakdown voltages of the MOCVD grown NiO/β-Ga2O3 PN diodes were measured as 348 and 267 V for the 100 and 200 μm diameter devices, respectively. The knee voltages (Vknee) were extracted as 4.7–5.2 V.