MBE growth of ZnSSeO alloy using ZnS as a sulfur source

Abstract

We have grown quaternary alloy semiconductor ZnSSeO by molecular beam epitaxy. Large band gap bowing due to large electronegativity of O is expected in this alloy. The growth of ZnSSeO was proceeded by supplying RF-excited oxygen during the growth of ZnSSe. The lattice constant of ZnSSeO decreased with increasing O 2 flow rate. X-ray diffraction peak was separated when O 2 flow rate was high. However, controllable range of lattice constant without phase separation was expanded compared with ZnSeO ternary alloy. It was shown that S composition parasitically increased with O composition. We have explained the enhancement of S incorporation in terms of reduction of strain energy. The band gap energy decreased with increasing O 2 flow rate regardless of phase separation. The amount of band gap bowing was slightly less than that found in ZnSeO. We have grown ZnSeO alloy by molecular beam epitaxy (MBE) and found large band gap bowing [4]. In ZnSeO ternary alloy, however, O composition influences both band gap energy and lattice constant. In order to control the band gap energy keeping the lattice constant fixed, a quaternary alloy is necessary. Moreover, phase separation was found in high O composition ZnSeO alloy due to a 19 % difference in bond length between ZnO and ZnSe [5]. In this work, we have grown ZnSSeO quaternary alloy. The smaller difference in bond length between ZnO and ZnS (15 %) than that between ZnO and ZnSe is advantageous in suppressing the internal lattice strain.

Composition control of ZnSSeO quaternary alloys grown on GaP

“…1) to 34 % only by the supply of O. This parasitic increase of S with O supply was observed for other T ZnS and T Se , and can be explained as the reduction of strain, since the bond-length-mismatch between ZnS and ZnO (15 %) is less than that between ZnSe and ZnO (19 %) [3].…”

“…For the practical application, quaternary alloy such as ZnSSeO is expected to be more useful since band gap energy can be tuned keeping the lattice constant fixed. In the previous study, we have grown ZnSe-based ZnSSeO alloys (S concentration less than 10 %) on GaAs and investigated the O 2 flow rate dependence of O concentration [3]. The band gap bowing was observed as that seen in ZnSeO.…”

X-ray absorption and diffraction study of II–VI dilute oxide semiconductor alloy epilayers

“…In an effort to control independently band gap and lattice parameter, one of the present authors has grown ZnSeOS quaternary alloys [8]. Indeed, the effect of small concentrations of S and O on the band gap of ZnSe is expected to be similar, while, compared to wurtzite ZnO, ZnS has a zinc-blende structure and a lattice parameter which is relatively close to that of ZnSe.…”