Search

A guard ring (GR) was employed to improve the breakdown voltage (Vbr) of vertical Ga2O3 Schottky barrier diodes (SBDs) with or without a field-plate (FP) by eliminating electric field concentration at the edges of anode and FP electrodes. The GR structure was formed by nitrogen (N)-ion implantation. Four types of vertical SBD structures with: 1) neither a GR nor a FP; 2) a GR; 3) a FP; and 4) both a GR and a FP were fabricated on the same substrate. The SBDs with a GR [structures 2) and 4)] showed largerVbr values than their GR-free counterparts [structures 1) and 3)]. Considering the trade-off relationship between Vbr and specific on-resistance (Ron), a Vbr/Ron combination of 1.43 kV/4.7 m · cm2 for the GR/FP-SBD corresponds to one of the best balanced data for Ga2O3 SBDs.

The thermal stability of +/- c- and m-plane GaN substrates and its dependence on the m-plane GaN off-cut angle were investigated at and above 1200 degrees C at atmospheric pressure in flowing N-2 with and without added NH3. It was clarified that decomposition of the +c-plane GaN surface is promoted by the addition of NH3, while decomposition of the -c- and m-plane GaN surfaces is suppressed by added NH3. It was found that -c- and m-plane GaN substrates can be heated at 1300 degrees C with an added NH3 input partial pressure of more than 0.2 atm, which is 100 degrees C higher than for +c-plane GaN substrates. Nevertheless, decomposition of m-plane GaN substrates became noticeable with increase in the off-cut angle of the substrate. It was revealed that the decomposition was better controlled by using m-plane GaN substrates with an off-cut towards [000 (1) over bar] than towards [0001]. (C) 2019 The Japan Society of Applied Physics

Gallium oxide (Ga2O3) has emerged as a new competitor to SiC and GaN in the race toward next-generation power switching and harsh environment electronics by virtue of the excellent material properties and the relative ease of mass wafer production. In this proceedings paper, an overview of our recent development progress of Ga2O3 metal-oxide-semiconductor field-effect transistors and Schottky barrier diodes will be reported. © Copyright 2018 SPIE.

Historically, the exploration of III-V compound semiconductors has begun with small bandgap materials and proceeded to large bandgap ones in recent years, that is, from GaAs-based compounds to GaN-based ones. We consider that gallium oxide (Ga2O3) is no exception in following this history and is poised to become the next mainstream of compound semiconductor research due to its attractive material properties based on an extremely large bandgap of about 4.5 eV [1]. This bandgap energy is not only much larger than those of representative wide bandgap semiconductors such as GaN and SiC but also unique among single-crystal semiconductors. Furthermore, Ga2O3 has another important advantage for commercialization over the other wide bandgap materials in that large-size, high-quality bulk single crystals can be synthesized by melt growth methods, thus allowing native substrates to be produced at a relatively low cost [2]. Recently, these two features have drawn much attention to Ga2O3, resulting in a rapid expansion of the Ga2O3 community. © 2018 IEEE.

Silicon doped homoepitaxial films were grown on beta-gallium oxide (001) substrates by halide vapor phase epitaxy using gallium monochloride, oxygen and silicon tetrachloride gases as precursors. It was confirmed that the n-type carrier density at room temperature was almost equal to the doped silicon concentration, which was controlled in the range of 10(15) to 10(18) cm(-3). In the doped film with the carrier density of 1x10(16) cm(-3), the activation energy and the mobility at room temperature were 45.6 meV and 145 cm(2)/V.s, respectively. The carrier scattering mechanism in the low carrier density film was dominated by optical phonon scattering with the phonon energy of 33 meV. These results suggest that the doped homoepitaxial film grown by halide vapor phase epitaxy is a high quality film with good crystallinity comparable to bulk crystals., Funding Agencies|Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "Next-generation power electronics" (funding agency: NEDO)

Homoepitaxial growth of p-Ga2O3 layers by halide vapor phase epitaxy (HVPE) using O-2 or H2O as an oxygen source was investigated by thermodynamic analysis, and compared with measured properties after growth. The thermodynamic analysis revealed that Ga2O3 growth is expected even at 1000 C-degrees using both oxygen sources due to positive driving forces for Ga2O3 deposition. The experimental results for homoepitaxial growth on (0 0 1) beta-Ga2O3 substrates showed that the surfaces of the layers grown with H2O were smoother than those grown with O-2, although the growth rate with H2O was approximately half that with O-2. However, in the homoepitaxial layer grown using H2O, incorporation of Si impurities with a concentration almost equal to the effective donor concentration (2 x 10(16)cm (3)) was confirmed, which was caused by decomposition of the quartz glass reactor due to the presence of hydrogen in the system. (C) 2018 Elsevier B.V. All rights reserved., Funding Agencies|Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "Next-generation power electronics" (funding agency: NEDO); Japan Society for the Promotion of Science [16H06417, 16K04944]

We investigated the temperature-dependent electrical properties of Pt/Ga2O3 Schottky barrier diodes (SBDs) fabricated on n(-)-Ga2O3 drift layers grown on single-crystal n(+)-Ga2O3 (001) substrates by halide vapor phase epitaxy. In an operating temperature range from 21 degrees C to 200 degrees C, the Pt/Ga2O3 (001) Schottky contact exhibited a zero-bias barrier height of 1.09-1.15 eV with a constant near-unity ideality factor. The current-voltage characteristics of the SBDs were well-modeled by thermionic emission in the forward regime and thermionic field emission in the reverse regime over the entire temperature range. (C) 2016 AIP Publishing LLC., Funding Agencies|Council for Science, Technology and Innovation (CSTI); NEDO