Highly Responsive, Polarization Sensitive, Self-Biased Single GeO2-Ge Nanowire Device for Broadband and Low Power Photodetectors

Highly uniform and dense GeO2 nanowires with Ge as the core were grown on Si (001) substrates by vapor–liquid–solid technique with an aim to utilize GeO2 as the active material for photodetectors. X-ray photoelectron spectroscopy was carried out to investigate the composition and interfaces of the resultant Ge/GeO2 NWs. The observed broad and visible photoluminescence emission from as-grown core–shell NW heterostructure is attributed to oxygen-related defect states in the GeO2 shells. Single Ge-GeO2 NW based metal–semiconductor–metal photodetectors were fabricated using nanolithography techniques. Self-driven (zero bias) detectors have been found to be responsive to a broadband spectrum from 350 to 900 nm with a peak responsivity (∼0.6 × 104 A/W) and detectivity (∼3.8 × 1012 Jones). The high gain in photocurrent has been explained using a back-to-back metal–semiconductor junction model in single NW. The device also shows sensitivity to polarization-dependence of light source. Finite element method (FEM) based optical simulation has been used to explain high and polarization dependent photoresponse of the single GeO2-Ge NW device.