Process Development for Wet-Chemical Surface Functionalization of Gallium Arsenide Based Nanowires

The chemisorption of various functionalizing agents on (100) and (111)B gallium arsenide and (100) indium phosphide substrates is studied to elaborate a wet-chemical surface coating protocol for gallium arsenide based nanowires. Application of (non-)fluorinated alkanethiols under different parameters shows great success resulting in a decreased polarity of the surface (confirmed by a significant increase of the water contact angle) and no occurrence of etching effects. The successful functionalization is determined by X-ray photoelectron spectroscopy measurements. After optimization of concentration, additives and solvents, the process parameters are transferred to both, p- and n-doped GaAs-based nanowire structures. The influence of surface functionalization on the electrical behavior of the nanowires is determined by current-voltage characteristics. Based on the experimental data, a bonding mechanism for the alkanethiol onto the semiconductor material is proposed and a model for describing surface depletion before and after functionalization is developed.