Nonlinear transport in GaAs and HgCdTe by photomixing

The carrier lifetime, mobility, and drift velocity are the important parameters of photoconductors. Normally, several independent tests such as conductivity, Hall effect, and decay of photoconductivity, etc., are used to measure these parameters separately. Pc decay sometimes becomes size limited, however, quite a lot of device configurations have small dimensions. Particularly, at low temperature pc decay may be nonexponential, that leads to some errors in the measurement. We applied the photo-mixing technique to measure the transport parameters. When a multimode laser beam is incident upon the photoconductor sample, the carrier generation rate of the sample will contain frequency components made up of the sum, difference, harmonics, and dc components of the incident frequencies as a bias is applied to the sample. We have generalized the theory of photo-mixing for the case of an unmode-locked multimode laser light incident upon a semiconductor. The results yield the photocurrent as a sum of a dc and an ac part.