Oxygen incorporation in wide band gap semiconductor ZnSe thin films

Abstract

Oxygen incorporation into ZnSe thin films in Ar/O2 or O2 ambient during radio-frequency sputtering was studied in this paper. With the increase of oxygen partial pressure ratio, the poor crystalline quality occurred in the films accompanying with a SeO2 secondary phase. The values of optical band gap for the films increased after light oxygen doping, ranging from 2.65 to 2.88 eV, which indicates the formation of ZnSeO ternary compounds. The near-band edge emission was observed in all samples, i.e., electronic transitions from the valence band to the conduction band. Nevertheless, heavy incorporation of O in ZnSe thin films led to the formation of the thin films with wide energy band gap (∼5.61 eV) and high optical transmittance (∼90%). X-ray photoelectron spectroscopy spectra indicate that oxygen atoms ionized by plasma enhanced the formation of SeO2 bonds with Se of ZnSe under the non-equilibrium conditions and many oxygen ions incorporated in the random sites, resulting in the formation of amorphous states.