SiGe Quantum Dots Over Si Pillars for Visible to Near-Infrared Broadband Photodetection

We demonstrate a successful selective growth of Si_0.3Ge_0.7 quantum dots (QDs) over array of p⁺-Si nanopillars using a low-pressure chemical vapor deposition technique, and hereafter realized high-performance QD broadband photodiodes for visible to near-infrared photodetection based on heterostructures of indium tin oxide/Si_0.3Ge_0.7 QD/Si pillar. Thanks to effective hole confinement and thus a built-in electric field within the SiGe QD, high ratios of photocurrent to dark current of ~2200, 100, and 30, respectively, were measured on our SiGe QDs-based photodiodes under illumination of 9 mW/cm² at wavelength of 500-800, 1300, and 1500 nm. The QD photodiode exhibits a very low dark current density of 3.2 × 10^-8 A/cm² and a tunable power-dependent linearity by applied voltage through the competition of electron drift and carrier recombination processes.