Ge nanowire photodetector with high photoconductive gain epitaxially integrated on Si substrate

Efficient nanoscale photodetectors are desirable for future applications such as on-chip optical interconnect systems. High density integration, ideally at the transistor level, requires nanoscale photodetectors integrated on Si using a CMOS compatible process. In this study, we demonstrate 20 nm diameter Ge photodetectors based on individual Ge nanowires epitaxially grown on a Si substrate, with a photoconductive gain of 2000 and responsivity of 22.6 A/W operating at 1.55 mu m wavelength. The abrupt heterojunction between the Ge nanowire and the Si substrate minimizes the leakage current including generation/recombination and tunneling. The photocurrent amplification can be attributed to the long lifetime of surface state trapped electrons in the Ge nanowires and Ge/Si core/shell nanowires. By increasing the number of active nanowires connected in parallel in a single detector, the photocurrent can be further increased. Published by AIP Publishing.