Synthesis and control of conductivity of ultraviolet transmitting beta-Ga2O3 single crystals

beta-Ga2O3 single crystals were grown by the floating zone method and their conductivity along the b axis was controlled from < 10(-9) to 38 Omega(-1) cm(-1) by changing the growth atmosphere. By using feed rods doped with Sn, the grown crystal became highly conductive even under oxidative atmosphere. The optical transmission spectra showed that the beta-Ga2O3 single crystal with 0.32 mm was transparent in the visible and ultraviolet region, with 20% transmittance at the fourth-harmonic wave of the Nd:YAG laser (266 nm). The band-gap widening was observed with the increasing of the carrier concentration. It is expected that the light of the KrF laser can be transmitted in the heavily doped beta-Ga2O3. (C) 1997 American Institute of Physics.