Low-Temperature Operation of High-Efficiency Germanium Quantum Dot Photodetectors in the Visible and Near Infrared

摘要

High-responsivity, low-noise CMOS-compatible photodetectorsrn(PDs) are required for applications such as optical interconnectsrnon silicon chips and for imaging sensors. Crystalline Gernis compatible with the Si fabrication technology and isrncharacterized by lower synthesis temperatures, a larger absorptionrncoefficient, because of its smaller bandgap, and a largerrnexcitonic Bohr radius, which allows better modulation of itsrnbandgap with size. For these reasons, Ge has been a widelyusedrnmaterial for CMOS-compatible PD fabrication.[1–4] Apartrnfrom its crystalline form, a variety of Ge nanostructuresrnhave been investigated for improved optoelectronicrnperformance[4–10] including Ge QDsrnembedded in an oxide matrix for highefficiencyrnphotodetection.[5,10–17] Thernprincipal advantages of Ge QDs includernreduced phonon scattering, leading tornlonger carrier relaxation times, as well asrnconfinement in all three spatial dimensionsrnthat can reduce the dark current,rnboth contributing to higher SNR. Furthermore,rnGe QDs are characterized by arntunable bandgap which allows broadrnwavelength selection, from the near-IR tornthe visible, and finally intersubband transitionsrnare polarization independent inrncontrast to quantum wells. Typically, Gernphotodetectors are operated at cryogenicrntemperatures in order to suppress therndark current, arising from thermallygeneratedrncarriers due to its smallerrnbandgap. In this work we have studiedrnthe temperature-dependent photoresponsernand noise performance over the 100–300 Krnrange in the visible and near-IR, ofrnCMOS-compatible PDs based on GernQDs embedded in an SiO2 matrix as introduced in our previousrnwork.[18]