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The cooling power limitations of superconductor-semiconductor junctions

Overview

The project is to model the factors limiting the cooling power of superconductor-semiconductor junctions and suggest ways to minimise their effect. These factors include (but are not limited to) quasiparticle backtunneling, ohmic heating and Andreev reflection.

Motivation

A multitude of devices need low temperature surroundings for optimal performance. Perhaps the types of device for which low temperature operation is most crucial are sensitive optical measurement apparata, which a high temperature (noisy) background would clearly interfere with. Getting to a temperature of the order 100mK in satellite and spacecraft based detectors is a particular problem, since achieving such temperatures currently requires a cryostat. These devices are large and complicated, and consequently are difficult to get into orbit.

An alternative could be a superconductor-semiconductor junction fabricated on a small silicon chip. By applying a bias voltage corresponding to the superconducting energy gap, the Fermi energies in the superconductor and semiconductor can be shifted such that 'hot' electrons can be extracted from the semiconductor, and replaced by 'cold' electrons, thus cooling the semiconductor.

If the processes limiting this 'cooling power' can be better understood and reduced, then the chips could be applied to these detectors, as well as many other areas e.g. quantum comptuing and medical diagnosis.

Supervisors:

Terry Whall

T dot E dot Whall at warwick dot ac dot uk

Terry Whall's research profile

Evan Parker

Evan dot Parker at warwick dot ac dot uk

Evan Parker's research profile

Co-worker:

James Richardson-Bullock

J dot R dot Bullock at warwick dot ac dot uk