Optical Response of Strained- and Unstrained-Silicon Cold-Electron Bolometers

We describe the optical characterisation of two silicon cold-electron bolometers each consisting of a small (32×14μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$32\,\times \,14~\mathrm {\upmu m}$$\end{document}) island of degenerately doped silicon with superconducting aluminium contacts. Radiation is coupled into the silicon absorber with a twin-slot antenna designed to couple to 160-GHz radiation through a silicon lens. The first device has a highly doped silicon absorber, the second has a highly doped strained-silicon absorber. Using a novel method of cross-correlating the outputs from two parallel amplifiers, we measure noise-equivalent powers of 3.0×10-16\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3.0 \times 10^{-16}$$\end{document} and 6.6×10-17WHz-1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$6.6 \times 10^{-17}~\mathrm {W\,Hz^{{-1}/{2}}}$$\end{document} for the control and strained device, respectively, when observing radiation from a 77-K source. In the case of the strained device, the noise-equivalent power is limited by the photon noise.