Ge Nanowires (Ge NWs) on single crystal, (100) and (111) oriented n-type Si substrates were grown via the vapor-liquid-solid (VLS) mechanism and studied with respect to their electrical properties.

Using different contact geometries, direct current (DC) and alternating current (AC) electrical and photoelectrical measurements were carried out at room temperature to investigate electrical properties of Ge NWs and Ge NWs/Si substrate one-dimensional (1 D) heterojunctions (HJs). A rectifying junction behavior is observed at NWs/substrate interface, but many orders of magnitude greater AC conductance than DC in Ge NW volume is measured at high frequencies. The obtained experimental data are consistent with the result of structural and optical studies and support the conclusion that the Ge NWs/Si substrate interface is nearly defect free while most of the structural defects in the form of twin dislocations are located within Ge NW volume. These defects control optical and carrier transport properties in the Ge NW volume. In addition, the frequency dependent AC conductance shows a power law behavior, suggesting that carrier transport in Ge NW volume is associated with hopping processes.