Determination of Nano Fluctuations in Surface Oxides of GaSb With Br-IBAE

Abstract

ABSTRACTHigh-quality substrates with thin uniform oxide layers are critical to the development of low-power epitaxy-based GaSb electronic and electro-optic devices. In this material system, the thickness and elemental composition of the oxide layers are a strong function of the surface preparation method. Here, a figure of merit for quantifying the thickness and thickness variations of an oxide layer on GaSb has been developed using bromine ion beam assisted etching (Br-IBAE). Furthermore, the overall thickness and composition of the oxide determines the etch depth for a fixed set of Br-IBAE parameters. The etch rate in GaSb was determined to be ∼395nm/min and that of its surface oxides was measured to be between 1.86 to 4.2nm/min. Hence, due to the difference in etch rates, nano fluctuations of the oxide thickness at the oxide surface and at the substrate/oxide interface, result in amplified roughness fluctuations in the etched GaSb substrate. The average roughness of Br-IBAE etched surfaces is used as figures of merit to quantify the uniformity and smoothness of the oxide layer. To demonstrate this, GaSb surfaces with various oxide layers and thicknesses were identically etched and their surface roughness measured using atomic force microscopy (AFM). This novel technique can generally be extended to a number of material systems.