More Like this

1. 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, Anhar (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. 

   more » « less
2. Ultrawide bandgap vertical β-(Al _x Ga _1−x ) ₂ O ₃ Schottky barrier diodes on free-standing β-Ga ₂ O ₃ substrates

   https://doi.org/10.1116/6.0002265  

   Mudiyanselage, Dinusha Herath; Wang, Dawei; Fu, Houqiang (March 2023, Journal of Vacuum Science & Technology A)

   Ultrawide bandgap β-(Al x Ga 1 −x ) 2 O 3 vertical Schottky barrier diodes on (010) β-Ga 2 O 3 substrates are demonstrated. The β-(Al x Ga 1 −x ) 2 O 3 epilayer has an Al composition of 21% and a nominal Si doping of 2 × 10 17  cm −3 grown by molecular beam epitaxy. Pt/Ti/Au has been employed as the top Schottky contact, whereas Ti/Au has been utilized as the bottom Ohmic contact. The fabricated devices show excellent rectification with a high on/off ratio of ∼10 9 , a turn-on voltage of 1.5 V, and an on-resistance of 3.4 mΩ cm 2 . Temperature-dependent forward current-voltage characteristics show effective Schottky barrier height varied from 0.91 to 1.18 eV while the ideality factor from 1.8 to 1.1 with increasing temperatures, which is ascribed to the inhomogeneity of the metal/semiconductor interface. The Schottky barrier height was considered a Gaussian distribution of potential, where the extracted mean barrier height and a standard deviation at zero bias were 1.81 and 0.18 eV, respectively. A comprehensive analysis of the device leakage was performed to identify possible leakage mechanisms by studying temperature-dependent reverse current-voltage characteristics. At reverse bias, due to the large Schottky barrier height, the contributions from thermionic emission and thermionic field emission are negligible. By fitting reverse leakage currents at different temperatures, it was identified that Poole–Frenkel emission and trap-assisted tunneling are the main leakage mechanisms at high- and low-temperature regimes, respectively. Electrons can tunnel through the Schottky barrier assisted by traps at low temperatures, while they can escape these traps at high temperatures and be transported under high electric fields. This work can serve as an important reference for the future development of ultrawide bandgap β-(Al x Ga 1 −x ) 2 O 3 power electronics, RF electronics, and ultraviolet photonics. 

   more » « less
3. 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. 

   more » « less
4. Effects of Downstream Plasma Exposure on β-Ga ₂ O ₃ Rectifiers

   https://doi.org/10.1149/2162-8777/ac0500  

   Xia, Xinyi; Xian, Minghan; Fares, Chaker; Ren, Fan; Kim, Junghun; Kim, Jihyun; Tadjer, Marko; Pearton, Stephen J. (June 2021, ECS Journal of Solid State Science and Technology)

   The effects of downstream plasma exposure with O 2 , N 2 or CF 4 discharges on Si-doped Ga 2 O 3 Schottky diode forward and reverse current-voltage characteristics were investigated. The samples were exposed to discharges with rf power of 50 W plasma at a pressure of 400 mTorr and a fixed treatment time of 1 min to simulate dielectric layer removal, photoresist ashing or surface cleaning steps. Schottky contacts were deposited through a shadow mask after exposure to avoid any changes to the surface. A Schottky barrier height of 1.1 eV was obtained for the reference sample without plasma treatment, with an ideality factor of 1.0. The diodes exposed to CF 4 showed a 0.25 V shift from the I–V of the reference sample due to a Schottky barrier height lowering around 14%. The diodes showed a decrease of Schottky barrier height of 2.5 and 6.5% with O 2 or N 2 treatments, respectively. The effect of plasma exposure on the ideality factor of diodes treated with these plasmas was minimal; 0.2% for O 2 and N 2 , 0.3% for CF 4 , respectively. The reverse leakage currents were 1.2, 2.2 and 4.8 μ A cm −2 for the diodes treated with O 2 , and CF 4 , and N 2 respectively. The effect of downstream plasma treatment on diode on-resistance and on-off ratio were also minimal. The changes observed are much less than caused by exposure to hydrogen-containing plasmas and indicate that downstream plasma stripping of films from Ga 2 O 3 during device processing is a relatively benign approach. 

   more » « less
5. Vertical β-Ga2O3 Schottky diodes with LPCVD-grown Sn-doped drift layer

   https://doi.org/10.1063/5.0319027  

   Khan, Saleh Ahmed; Ibreljic, Ahmed; Bhuiyan, Anhar (June 2026, APL Electronic Devices)

   High-quality Sn-doped (010) β-Ga2O3 homoepitaxial drift layers were grown by using the low-pressure chemical vapor deposition (LPCVD) method using solid elemental Sn as the n-type dopant source and integrated into vertical Ni/β-Ga2O3 Schottky barrier diodes to evaluate their device-level performance. β-Ga2O3 films with net carrier concentrations spanning from 2.0 × 1016 to 3.2 × 1017 cm−3 were achieved in thick epilayers exhibiting smooth surface morphology and high crystalline quality, as evidenced by surface rms roughness as low as 2.17 nm and an x-ray diffraction rocking-curve full width at half maximum as low as 38.9 arcsec. The fabricated diodes exhibited clear rectification and near-ideal thermionic-emission behavior, yielding ideality factors of 1.16–1.18 and Schottky barrier heights of 1.08–1.19 eV. The differential specific on-resistance (Ron,sp) decreased with increasing carrier concentration, with measured values ranging from 38.07 to 27.31 mΩ cm2. Temperature-dependent current–voltage measurements ranging from 25 to 250 °C showed stable thermionic-emission-dominated transport, with a gradual reduction in Schottky barrier height and an increase in on-resistance due to phonon-limited mobility. Capacitance–voltage (C–V) analysis confirmed uniform and controllable doping profiles and yielded barrier heights between 1.12 and 1.29 eV, depending on carrier concentration. Temperature-dependent C–V measurements revealed a systematic reduction in built-in potential and barrier height with increasing temperature. Reverse-bias measurements demonstrated a breakdown voltage of 225 V for a diode with a drift-layer carrier concentration of 2.0 × 1016 cm−3 in the absence of any field-management structures, with two-dimensional Silvaco technology computer-aided design (TCAD) electrostatic simulations revealing peak electric fields localized at the Schottky anode edge, indicating edge-field-limited breakdown. These results demonstrate LPCVD as a viable approach for the growth of Sn-doped β-Ga2O3 drift layers that support high-quality Schottky interfaces with stable operation over a wide temperature range, providing a foundation for continued development of β-Ga2O3 high power devices. 

   more » « less