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1. Gate leakage current and threshold voltage characteristics of β-Ga2O3 passivated AlGaN/GaN based heterojunction field effect transistor

   https://doi.org/10.1117/12.2668236  

   Hasan, Samiul; Jewel, Mohi Uddin; Crittenden, Scott R.; Lee, Dongkyu; Avrutin, Vitaliy S.; Özgür, Ümit; Morkoç, Hadis; Ahmad, Iftikhar (March 2023, Gallium Nitride Materials and Devices XVIII; 124210A (2023))

   Morkoç, Hadis; Fujioka, Hiroshi; Schwarz, Ulrich T. (Ed.)

   We report the gate leakage current and threshold voltage characteristics of Al0.3Ga0.7N/GaN heterojunction field effect transistor (HFET) with metal-organic chemical vapor deposition (MOCVD) grown β-Ga2O3 as a gate dielectric for the first time. In this study, GaN channel HFET and β-Ga2O3 passivated metal-oxide-semiconductor-HFET (MOS-HFET) structures were grown in MOCVD using N2 as carrier gas on a sapphire substrate. X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to characterize the structural properties and surface morphology of the heterostructure. The electrical properties were analyzed using van der Pauw, Hall, and the mercury probe capacitance-voltage (C-V) measurement systems. The 2-dimensional electron gas (2DEG) carrier density for the heterostructure was found to be in the order of ~1013 cm-2. The threshold voltage shifted more towards the negative side for the MOSHFET. The high-low (Hi-Lo) frequency-based C-V method was used to calculate the interface charge density for the oxide-AlGaN interface and was found to be in the order of ~1012 cm2eV-1. A remarkable reduction in leakage current from 2.33×10-2 A/cm2 for HFET to 1.03×10-8 A/cm2 for MOSHFET was observed demonstrating the viability of MOCVD-grown Ga2O3 as a gate dielectric. 

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2. Quasi-vertical β-Ga2O3 Schottky diodes on sapphire using all-LPCVD growth and plasma-free Ga-assisted etching

   https://doi.org/10.1063/5.0280191  

   Khan, Saleh_Ahmed; Ibreljic, Ahmed; Bhuiyan, A_F_M_Anhar_Uddin (September 2025, APL Electronic Devices)

   This work demonstrates quasi-vertical β-Ga2O3 Schottky barrier diodes (SBDs) fabricated on c-plane sapphire substrates using an all-low-pressure chemical vapor deposition (LPCVD)-based, plasma-free process flow that integrates both epitaxial growth of a high-quality β-Ga2O3 heteroepitaxial film with in situ Ga-assisted β-Ga2O3 etching. A 6.3 μm thick (2̄01) oriented β-Ga2O3 epitaxial layer structure was grown on c-plane sapphire with 6° miscut, comprising a moderately Si-doped (2.1 × 1017 cm−3) 3.15 μm thick drift layer and a heavily doped (1 × 1019 cm−3) contact layer on an unintentionally doped buffer layer. Mesa isolation was achieved via Ga-assisted plasma-free LPCVD etching, producing ∼60° inclined mesa sidewalls with an etch depth of 3.6 μm. The fabricated SBDs exhibited excellent forward current–voltage characteristics, including a turn-on voltage of 1.22 V, an ideality factor of 1.29, and a Schottky barrier height of 0.83 eV. The minimum differential specific on-resistance was measured to be 8.6 mΩ cm2, and the devices demonstrated high current density capability (252 A/cm2 at 5 V). Capacitance–voltage analysis revealed a net carrier concentration of 2.1 × 1017 cm−3, uniformly distributed across the β-Ga2O3 drift layer. Temperature-dependent J–V–T measurements, conducted from 25 to 250 °C, revealed thermionic emission-dominated transport with strong thermal stability. The Schottky barrier height increased from 0.80 to 1.16 eV, and the ideality factor rose modestly from 1.31 to 1.42 over this temperature range. Reverse leakage current remained low, increasing from ∼5 × 10−6 A/cm2 at 25 °C to ∼1 × 10−4 A/cm2 at 250 °C, with the Ion/Ioff ratio decreasing from ∼1 × 107 to 5 × 105. The devices achieved breakdown voltages ranging from 73 to 100 V, corresponding to parallel-plate electric field strengths of 1.66–1.94 MV/cm. These results highlight the potential of LPCVD-grown and etched β-Ga2O3 devices for high-performance, thermally resilient power electronics applications. 

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3. MOCVD growth of β-Ga2O3 with fast growth rates (>4.3 μ m/h), low controllable doping, and superior transport properties

   https://doi.org/10.1063/5.0238094  

   Yu, Dong Su; Meng, Lingyu; Zhao, Hongping (December 2024, Applied Physics Letters)

   Si-doped β-phase (010) Ga2O3 epi-films with fast growth rates were comprehensively investigated using trimethylgallium (TMGa) as the Ga precursor via metalorganic chemical vapor deposition (MOCVD). Two main challenges facing the MOCVD growth of thick (010) β-Ga2O3 films with fast growth rates include high impurity carbon (C) incorporation and rough surface morphologies due to the formation of imbedded 3D pyramid-shaped structures. In this work, two different categories of oxygen source (high-purity O2 > 99.9999% and O2* with 10 ppm of [H2O]) were used for β-Ga2O3 MOCVD growth. Our study revealed that the size and density of the 3D defects in the β-Ga2O3 epi-films were significantly reduced when the O2* was used. In addition, the use of off-axis (010) Ga2O3 substrates with 2° off-cut angle leads to further reduction of defect formation in β-Ga2O3 with fast growth rates. To suppress C incorporation in MOCVD β-Ga2O3 grown with high TMGa flow rates, our findings indicate that high O2 (or O2*) flow rates are essential. Superior room temperature electron mobilities as high as 110–190 cm2/V·s were achieved for β-Ga2O3 grown using O2* (2000 sccm) with a growth rate of 4.5 μm/h (film thickness of 6.3 μm) within the doping range of 1.3 × 1018–7 × 1015 cm−3. The C incorporation is significantly suppressed from ∼1018 cm−3 to <5 × 1016 cm−3 ([C] detection limit) for β-Ga2O3 grown using high O2 (O2*) flow rate of 2000 sccm. Results from this work will provide guidance on developing high-quality, thick β-Ga2O3 films required for high power electronic devices with vertical configurations. 

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4. Characterization of (001) β -Ga2O3 Schottky diodes with drift layer grown by MOCVD

   https://doi.org/10.1063/5.0155622  

   P. Sundaram, Prakash; Liu, Fengdeng; Alema, Fikadu; Osinsky, Andrei; Jalan, Bharat; Koester, Steven J. (June 2023, Applied Physics Letters)

   Growing a thick high-quality epitaxial layer on the β-Ga2O3 substrate is crucial in commercializing β-Ga2O3 devices. Metal organic chemical vapor deposition (MOCVD) is also well-established for the large-scale commercial growth of β-Ga2O3 and related heterostructures. This paper presents a systematic study of the Schottky barrier diodes fabricated on two different Si-doped homoepitaxial β-Ga2O3 thin films grown on Sn-doped (001) and (010) β-Ga2O3 substrates by MOCVD. X-ray diffraction analysis of the MOCVD-grown sample, room temperature current density–voltage data for different Schottky diodes, and C–V measurements are presented. Diode characteristics, such as ideality factor, barrier height, specific on-resistance, and breakdown voltage, are studied. Temperature dependence (170–360 K) of the ideality factor, barrier height, and Poole–Frenkel reverse leakage mechanism are also analyzed from the J–V–T characteristics of the fabricated Schottky diodes. 

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5. Electrical and structural characterization of in situ MOCVD Al2O3/β-Ga2O3 and Al2O3/β-(AlxGa1−x)2O3 MOSCAPs

   https://doi.org/10.1063/5.0256525  

   Bhuiyan, A_F_M_Anhar Uddin; Meng, Lingyu; Yu, Dong Su; Dhara, Sushovan; Huang, Hsien-Lien; Vangipuram, Vijay_Gopal Thirupakuzi; Hwang, Jinwoo; Rajan, Siddharth; Zhao, Hongping (May 2025, Journal of Applied Physics)

   This study investigates the electrical and structural properties of metal–oxide–semiconductor capacitors (MOSCAPs) with in situ metal-organic chemical vapor deposition-grown Al2O3 dielectrics deposited at varying temperatures on (010) β-Ga2O3 and β-(AlxGa1−x)2O3 films with different Al compositions. The Al2O3/β-Ga2O3 MOSCAPs exhibited a strong dependence of electrical properties on Al2O3 deposition temperature. At 900 °C, reduced voltage hysteresis (∼0.3 V) with improved reverse breakdown voltage (74.5 V) was observed, corresponding to breakdown fields of 5.01 MV/cm in Al2O3 and 4.11 MV/cm in β-Ga2O3 under reverse bias. In contrast, 650 °C deposition temperature resulted in higher voltage hysteresis (∼3.44 V) and lower reverse breakdown voltage (38.8 V) with breakdown fields of 3.69 and 2.87 MV/cm in Al2O3 and β-Ga2O3, respectively, but exhibited impressive forward breakdown field, increasing from 5.62 MV/cm at 900 °C to 7.25 MV/cm at 650 °C. High-resolution scanning transmission electron microscopy (STEM) revealed improved crystallinity and sharper interfaces at 900 °C, contributing to enhanced reverse breakdown performance. For Al2O3/β-(AlxGa1−x)2O3 MOSCAPs, increasing Al composition (x) from 5.5% to 9.2% reduced net carrier concentration and improved reverse breakdown field contributions from 2.55 to 2.90 MV/cm in β-(AlxGa1−x)2O3 and 2.41 to 3.13 MV/cm in Al2O3. The electric field in Al2O3 dielectric under forward bias breakdown also improved from 5.0 to 5.4 MV/cm as Al composition increased from 5.5% to 9.2%. The STEM imaging confirmed the compositional homogeneity and excellent stoichiometry of both Al2O3 and β-(AlxGa1−x)2O3 layers. These findings demonstrate the robust electrical performance, high breakdown fields, and excellent structural quality of Al2O3/β-Ga2O3 and Al2O3/β-(AlxGa1−x)2O3 MOSCAPs, highlighting their potential for high-power electronic applications. 

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