High-Hall-electron-mobility and high-performance Schottky barrier diodes for edge-defined fed-grown () β-Ga2O3 single crystals have been demonstrated. A high electron mobility of 886 cm2/(V·s) at 85 K was obtained. By theoretical specific scattering mechanisms, it was found that the electron mobility for >200 K is limited by optical phonon scattering and that for <100 K by ionized impurity scattering. On Schottky barrier diodes with Ni contacts, the current density for the forward voltage was 70.3 A/cm2 at 2.0 V, and a nearly ideal ideality factor of 1.01 was obtained.

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The channel layer substitution of a wider bandgap AlGaN for a conventional GaN in high electron mobility transistors (HEMTs) is an effective method of enhancing the breakdown voltage. We demonstrated a remarkable breakdown voltage enhancement in these AlGaN channel HEMTs. The obtained maximum breakdown voltages were 463 and 1650V in the Al0.53Ga0.47N∕Al0.38Ga0.62N HEMT with the gate-drain distances of 3 and 10μm, respectively. This result is very promising for the further higher power operation of high-frequency HEMTs.

A β-(AlxGa1−x)2O3:Si/Ga2O3 modulation-doped structure was fabricated by direct β-(AlxGa1−x)2O3 epitaxial growth on a (010) β-Ga2O3 substrate. Si on the order of 1018 cm−3 from adsorbed contaminants on the substrate surface was doped into the β-(AlxGa1−x)2O3 layer. The heterojunction interface exhibited a confined sheet carrier density of ∼3 × 1012 cm−2, which is on the same order as that of AlGaAs/GaAs. The successful modulation doping for the β-(AlxGa1−x)2O3/Ga2O3 heterostructure encourages the development of β-Ga2O3-based heterojunction field-effect transistors.

We fabricated Schottky barrier diodes (SBDs) on the entire surface of a ð010Þ β-Ga 2 O 3 single crystal, and investigated the leakage current in both forward and reverse directions. Subsequently, we investigated the distribution of dislocation and void etch pits on the entire surface. The dislocation etch pit density on the surface ranged from <1 ' 10 3 to 6 ' 10 4 , and its average was 1.1 ' 10 4 cm %2 . The void etch pit density on the surface ranged from <5 ' 10 2 to 7 ' 10 3 , and its average was 6 ' 10 3 cm %2 . From a comparison between the SBD leakage current and the dislocation and void etch pit densities, we found that dislocations are closely related to the SBD reverse leakage current, and that not all voids produce the leakage current.