High electron mobility In2O3(001) and (111) thin films with nondegenerate electron concentration

Temperature dependent Hall measurements were applied to demonstrate, semiconducting n-type high-quality In2O3(001) and (111) thin films with nondegenerate unintentionally doped (UID) electron concentrations on the order of 1017 cm−3 at room temperature, which is below those of bulk single crystals. The freeze-out of the electron concentration in all samples suggests a shallow UID donor with ionization energy in the 17 meV range. Postgrowth annealing in oxygen allowed to further decrease the UID electron concentration with simultaneous mobility increase, suggesting oxygen vacancies to be the shallow UID donors. Hall mobilities above 200 cm2/V s at room temperature and 1000 cm2/V s at low temperatures exceed those of bulk single crystals and demonstrate high material quality and purity.