Electrical Characterization of Metal–Silicon Microwire Interface Using Conductive Atomic Force Microscope

Abstract

Ni-catalyzed silicon microwires (SiMWs) were grown on n-Si(111) substrate. The bottom contacts of the SiMWs were selectively formed using Ni electrodeposition at the substrate. The current–voltage (I–V) characteristics of the microwires were measured using conductive atomic force microscope (CAFM). Different charge transport models such as thermionic-emission, field-emission and thermionic-field-emission were applied to the measured I–V characteristics of the metal–SiMW–metal structures in the array. It was observed that the thermionic-field-emission and field-emission were the leading Schottky transport mechanisms needed to explain the measured I–V responses in forward and reverse bias respectively. By applying the thermionic-field-emission model to the measured I–V characteristics of SiMW array, parameters such as conductivity, free carriers density and mobility were estimated and discussed. It was also observed that the average estimated mobility of the carriers in SiMW array was lower than the reported bulk mobility. It may be due to the fact that higher aspect ratio, nonliner doping concentration both at radial as well as axial direction of SiMWs and surface scattering of the carriers were dominant and hence it degraded the mobility of the SiMW array.