Oscillatory photoconductivity from shallow donors in n-type CdTe

Pronounced minima separated by half the frequency of the longitudinal optical phonon have been observed in the frequency dependence of the low-temperature extrinsic photoconductivity of n-type CdTe. This observation is attributed to the occurrence of two separate and distinct series of minima, each series being spaced by the frequency of the longitudinal optical phonon, which was found to be 171·4 cm -1 . Both series amount to almost 100% modulation of the photoconductive response, and are therefore interpreted as arising from two alternative capture processes rather than from simultaneous excitation from two different impurity levels. The amplitude of the oscillatory response was found to be a strong function of the wavelength of the incident radiation, with the photoconductive response per unit power varying with frequency to the power of -4·9.