AN INVESTIGATION OF MBE GROWTH OF (ZN,MG)SE USING RHEED OSCILLATIONS

We have used reflection high-energy electron diffraction (RHEED) oscillations to measure the growth rates of Zn1-xMgxSe and ZnSe as functions of substrate temperature, II/VI flux ratio, and electron-beam filament current. Although the ZnSe and Zn1-xMgxSe growth rates vary with these growth parameters, the growth rate difference attributable to the addition of magnesium does not depend on them, if growth is done with a selenium excess. Thus, unlike the other common components of II/VI materials (Zn, Cd, S, Se and Te), the sticking coefficient of magnesium is independent of substrate temperature and II/VI flux ratio. Electron-beam-induced desorption of magnesium is also negligible. For growth with a selenium excess, the composition of Zn1-xMgxSe films determined by RHEED oscillations agrees well with X-ray fluorescence measurements. However, if growth is done without an excess of selenium, then a simple composition calculation using the Zn1-xMgxSe and ZnSe growth rates indicates a magnesium content which is lower than the true magnesium content. This occurs because of a decrease in the sticking coefficient of zinc induced by the presence of magnesium.