Control of intrinsic defects in molecular beam epitaxy grown CuInSe2

CuInSe2 epitaxial films have been grown by molecular beam epitaxy at a subtrate temperature of T-S = 450 degrees C. The vacancy-type defects which dominate the properties of the CuInSe2 films have been characterized and methods to control defects have been investigated. Films grown under In-flux excess conditions tend to show nonideal crystalline quality; the films are highly compensated with a high density of twins. Post-growth annealing of the films in air substantially reduced the twin density as well as the degree of compensation, implying that there is a strong correlation between Se-vacancies and the density of twins. Such improvement in the film quality was found to be responsible for in-diffused oxygen from the surface during the air-annealing process, and oxygen is considered to substitute for Se vacancies. The preliminary results showed that in situ incorporation of oxygen during the molecular beam epitaxial growth of CuInSe2 films made possible the reduction of twin densities. (C) 1999 Published by Elsevier Science B.V. All rights reserved.