Control of surface morphology and electronic properties of III-V semiconductors using molecular modification

Abstract

GaAs surface was modified by self-assembled monolayer of organic molecules through wet chemical processes, which include etching and coating. Octadecanethiol (ODT) and benzenethiol (BT) were the choice as modifiers. Etched surface of the GaAs, whose quality greatly affects the morphology and properties of the resulting modified GaAs, was investigated by x-ray photoelectron spectroscopy combined with atomic force microscopy (AFM). Nanometer-scale particlelike structures of Ga2O3 appeared on the surface after etching by etchant with low acid concentration. The particle size was controllable by the acid concentration and etching time. Almost the entire surface of the GaAs substrate was successfully covered with thiol molecules when GaAs etched by the etchant with high acid concentration was used. The conduction of the ODT-coated GaAs measured with conductive prove AFM using Rh coated cantilevers was below the detection limit of the current amplifier. However, current-voltage characteristics of BT-coated GaAs showed electron rectification proving electron transport via the π-orbital. The molecular modification of the semiconductors by wet chemical processes may afford a promising route to control the surface states of organic molecule-semiconductor interface for novel device structures.