Modulated contrast and associated diffracted intensity of GaPySb1-y layers grown using organometallic vapor phase epitaxy

Abstract

We have investigated the modulated structures and its associated diffracted diffuse intensity, of organometallic vapor phase epitaxially grown GaPSb (001) layers by using transmission electron microscopy (TEM) and transmission electron diffraction (TED). The TEM results reveal the coexistence of a fine-scale modulated contrast and a fine-scale speckled contrast. In addition, a fine needle-like contrast is observed. The [001] TED results show lines of [110]-oriented diffuse intensity diffuse streaks passing through the fundamental reflections, satellite spots at 1/4g[220] positions, and a [010]-oriented diffuse intensity with spacing of 1/6g[040]. Simulations using the Valence Force Field model were performed to understand the origin of the diffracted features. The observed distributions of diffuse intensity are shown to be partially consistent with random disorder. Furthermore, the [110]-oriented diffuse lines are attributed to a static displacement of the sites of the mixed sublattices.