Surface state control of III–V semiconductors using molecular modification

An attempt to control surface electronics of III–V semiconductor using wet chemical processes has been performed. Here, we report results on the use of self-assembled monolayers (SAMs) of organic molecules on (0 0 1) GaAs surface. Octadecanethiol (ODT) and benzenethiol (BT) have been the choice in the present study. GaAs wafers were modified by thiol molecules on the flat surface after the native oxide layers are removed by chemical etching under optimized conditions. The change in the electronic properties was measured in terms of transport properties via the SAM layer by conductive probe atomic force microscopy. The current–voltage characteristics thus obtained show that ODT functions as a tunnel barrier while BT is conductive due to the presence of π-electrons. As a result, we can control the electronic states of GaAs–molecule interface for realizing novel device structures by the selection of functional molecules.