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

TL;DR

This study compares the optical response and noise performance of strained and unstrained silicon cold-electron bolometers, demonstrating improved sensitivity in the strained device limited by photon noise.

Contribution

It introduces a novel measurement method and provides the first comparison of strained versus unstrained silicon bolometers for 160-GHz radiation detection.

Findings

Strained silicon bolometer has lower noise-equivalent power than unstrained.

Noise in the strained device is limited by photon noise.

Both devices successfully detect 160-GHz radiation with high sensitivity.

Abstract

We describe the optical characterisation of two silicon cold-electron bolometers each consisting of a small ($32 \times 14~\mathrm{\mu m}$) 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 $3.0 \times 10^{-16}$ and $6.6 \times 10^{-17}~\mathrm{W\,Hz^{-1/2}}$ 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.