Low-Noise, High-Detectivity, Polarization-Sensitive, Room-Temperature Infrared Photodetectors Based On Ge Quantum Dot-Decorated Si-On-Insulator Nanowire Field-Effect Transistors

A CMOS-compatible infrared (IR; 1200-1700 nm) detector based on Ge quantum dots ( QDs) decorated on a single Si-nanowire channel on a silicon-on-insulator (SOI) platform with a superior detectivity at room temperature is presented. The spectral response of a single nanowire device measured in a back-gated field-effect transistor geometry displays a very high value of peak detectivity similar to 9.33 x 10(11) Jones at similar to 1500 nm with a relatively low dark current (similar to 20 pA), which is attributed to the fully depleted Si nanowire channel on SOI substrates. The noise power spectrum of the devices exhibits a 1/f(gamma), with the exponent, gamma showing two different values of 0.9 and 1.8 owing to mobility fluctuations and generation-recombination of carriers, respectively. Ge QD-decorated nanowire devices exhibit a novel polarization anisotropy with a remarkably high photoconductive gain of similar to 10(4). The superior performance of a Ge QDs/Si nanowire phototransistor in IR wavelengths is potentially attractive to integrate electro-optical devices into Si for on-chip optical communications.