Quantum dot Ge/TiO2 heterojunction photoconductor fabrication and performance

Abstract

Spun cast TiO2-Ge quantum dot (QD) heterojunction type photodetectors have been fabricated and characterized, with interest paid to photocurrent enhancements related to device design. Performance as a function of absorber layer thickness, QD size, and back contact is investigated. We have achieved ultra-thin (∼200 nm) devices with photocurrents at 0.5 V of 10−4 A cm−2 while the thickest devices have photocurrents at 0.5 V of 10−2 A cm−2 with on-off ratios >100, which represents 5 orders of magnitude increase in photocurrents over previously fabricated Ge QD devices. At 0.5 V bias, the currents in our devices are competitive with thin-film Ge photovoltaics.