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

We demonstrate a successful selective growth of Si
_0.3
Ge
_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
_0.3
Ge
_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/cm
²
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/cm
²
and a tunable power-dependent linearity by applied voltage through the competition of electron drift and carrier recombination processes.