Optical characterization by variable angle spectroscopic ellipsometry of nitrogen-doped Mg Zn1−O thin films prepared by the plasma-assisted reactive evaporation method

Abstract

substrates by the plasma-assisted reactive evaporation (PARE) method using ZnMg alloys. Optical parameters, refractive index n, extinction coefficient k, and absorption coefficient α of these films and ZnO substrate were easily estimated by variable angle spectroscopic ellipsometry. The k values of these films abruptly increased with increase in photon energy near the absorption edge region. Dispersions of n of these films were sharper with larger peak values than that of a ZnO substrate. Mg x Zn 1-x O films and Mg x Zn 1-x O:N films grown on a ZnO substrate by the PARE method are of high quality with less defects than those of a ZnO substrate. Maximum value of α of these films calculated from k was about 2×10 5 cm-1. The values of intercepts on photon energy hν axis of (αhν) 2-hν plots for these films and the ZnO substrate agree with peak energy of PL spectra, the origin of which is free excitons. These results indicate that absorption in those materials is dominated by exciton absorption.

Photoconductive properties of undoped and nitrogen‐doped ZnO single crystals in various ambiences

“…The reason for this is thought to be as follows. Since the absorption coefficient of the undoped ZnO single crystal is about 2×10 5 /cm [20], photocarriers are generated in a very thin area near the ZnO surface. Therefore, effect of surface recombination on the photocurrent is still strong.…”