Abstract
A series of IR 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 H2 or D2 at temperatures near 450°C produces an n-type layer ≈0.06 mm thick with an n-type doping of 1.6x1019 cm-3. The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm-3 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 an H-trapped oxygen vacancy is the dominant shallow donor (in ZnO and SnO2, for example), interstitial H+ is found to be the dominant H-related shallow donor in In2O3.