Quantum dot Ge/TiO_2 heterojunction photoconductor fabrication and performance

摘要

Spun cast TiO_2-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 (～200nm) 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.