Germanium Quantum Dot Optoelectronic Devices - Photodetectors

摘要

Using thermal oxidation of SiGe-on-insulator structures for forming Ge quantum dots (QDs) embedded in a SiO{sub}2 matrix, we have systematically investigated possible structure factors that would affect the properties of Ge QDs such as size, density, and even the position. Cathodeluminescence spectra reveal significant light emission at 400 - 600 nm from the Ge-QDs/SiO{sub}2 system as the QD size is scaled from 9 nm to 3 nm. This finding strongly motivates the exploration of Ge-QDs/SiO{sub}2 metal-oxide-semiconductor (MOS) photodiodes (PDs) for visible to near ultraviolet photodetection. MOS PDs with Ge QDs have high rectifying ratio (～10 ) in darkness and a high photocurrent/dark-current ratio (～10 ). Increasing the number of Ge-QD layers from zero, through one to three improves the photoresponsivity from 4.64, through 482 to 812 mA/W corresponding to quantum efficiencies of 1.42,148, and 245%, respectively.