Temperature dependence of the response time of bulk indium antimonide mixers

Conductivity modulation in n-type indium antimonide at liquid helium temperatures has proven to be useful in making millimeter wave mixers and detectors. The conductivity modulation arises from the heating of the electrons by the applied electric fields. An important material parameter characterizing this heating process is the electron energy relaxation time. Knowledge of this time allows one to determine the responsivity and response time of a detector or the conversion loss and maximum usable intermediate frequency of a mixer. Since the energy relaxation time in InSb at 4.2°K is approximately 10^-7sec. the intermediate frequency cannot be made higher than 1 MHz. In order to avoid noise close tO the nominal frequency of the local oscillator, it is important to investigate the operation of InSb mixers at higher ambient temperatures where shorter energy relaxation times have been observed.