Detection of millimetre and sub-millimetre wave radiation by free carrier absorption in a semiconductor

Abstract

Radiation absorbed by the free carriers in a semiconductor gives rise to an increase in the carrier temperature and a change of mobility. In n-type indium antimonide at liquid helium temperatures the effect is very pronounced and has been made the basis of a detector for millimetre and sub-millimetre wavelength radiation. The limiting sensitivity for a 1 c/s bandwidth is found to be similar 3 × 10-13 w at a temperature of 1.8° K, with a response time similar 10-7 sec.