Abstract
Crystal phase-selective epitaxy of Nb-doped TiO2 (TiO2:Nb) films on GaN is demonstrated using the helicon-wave-excited-plasma sputtering epitaxy method. On the clean (0001) GaN, rutile (100) TiO2: Nb was grown regardless of growth temperature (T-g). On the (0001) GaN covered with a monolayer-thick (100) or (001) beta-Ga2O3, anatase (001) TiO2:Nb was grown with the in-plane relation (110)TiO2 parallel to (1120)GaN under high T-g and low O-2 partial pressure conditions. The transmittance between 450 and 900nm for the 200-nm-thick films was approximately 80%. Typical resistivity of the anatase TiO2:Nb/GaN heterostructure was as low as 3.6 x 10(-4) Omega.cm, due to the interfacial conduction. (c) 2010 The Japan Society of Applied Physics