Optical properties of wide bandgap ZnHgSSe layers grown by molecular beam epitaxy

Abstract

Wide bandgap ternary Zn1 − xHgxSe (x = 0–0.14) and quaternary Zn1 − xHgxSySe1 − y (x = 0–0.03, y = 0–0.04) alloy layers have been grown on GaAs substrates by molecular beam epitaxy (MBE), and characterized by optical reflectance, absorption and photoluminescence. The layers show strong photoluminescence composed of a single emission band whose peak energy decreases rapidly with increasing Hg content x. For the Zn1 − xHgxSySe1 − y layers with small x and y, the origin of the emission band can be explained in terms of excitonic transitions. As to the layers with large x and y, however, a large discrepancy is found between the fundamental absorption edge and the emission band. This behavior is discussed in terms of localized tail states induced by the microscopic compositional fluctuation of the alloy layers.