Hydrogen centers and the conductivity of In2O3 single crystals

A series of infrared absorption experiments and complementary theory have been performed to determine the properties of OH and OD centers in In2O3 single crystals. Annealing In2O3 samples in H-2 or D-2 at temperatures near 450 degrees C produces an n-type layer approximate to 0.06mm thick with an n-type doping of 1.6 x 10(19) cm(-3). The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm(-1) that we associate with interstitial H+. Additional O-H (O-D) vibrational lines are assigned to metastable configurations of the interstitial H+ (D+) center and complexes of H (D) with In vacancies. Unlike other oxides studied recently where H trapped at an oxygen vacancy is the dominant shallow donor (ZnO and SnO2, for example), interstitial H+ is found to be the dominant H-related shallow donor in In2O3.