Development of Large Diameter Semi-Insulating Gallium Oxide (Ga2O3) Substrates

Beta-phase gallium oxide (β-Ga2O3) is an emerging ultra-wide bandgap semiconductor targeting next generation high power switching and high voltage RF electronics. β-Ga2O3 possesses a bandgap (Eg) of approximately 4.9 eV and a theoretical critical field strength (Ec) of 8 MV/cm. The breakdown field for β-Ga2O3 is 2 -3 times larger than that of silicon carbide (SiC) or gallium nitride (GaN). The Baliga figure of merit for β-Ga2O3 provides at least a factor of three against GaN and eight against SiC, respectively making it a promising low-loss power switch material. Breakdown voltages of 1.6 kV and 740 V have been achieved for β-Ga2O3 Schottky diodes and MOSFETs respectively. Lateral device electric fields of 3.8 MV/cm have also been demonstrated. Critical to this performance realization is the availability of native β-Ga2O3 substrates. β-Ga2O3 single crystals are produced by crystallization from a melt utilizing high growth rate processes such as Czochralski (CZ) or Edge-defined Film-fed Growth (EFG) techniques. Through Air Force Research Laboratory support, Northrop-Grumman SYNOPTICS has successfully scaled the growth of unintentionally doped (UID), Mg-doped and Fe-doped β-Ga2O3 crystals from self-nucleated polycrystalline grains on iridium wire to seeded (010) oriented 50-mm diameter boules. Efforts directed at establishing growth and fabrication processes will be reviewed.