Photoconductivity of a semiconductor with a transverse gradient of drift velocity of charge carriers

The spectral photosensitivity of a semiconductor with a gradient of the drift velocity of charge carriers has been investigated. It was found to be of either selective or bolometric type depending on mutual directions of incident light and of the gradient. Photoconductivity of germanium samples of ringlike geometry was studied experimentally over the spectral range 0.8–2.2 μm at room temperature. The main results are: decay of the photocurrent in a semiconductor where the gradient differs from the exponential one and depends on the mutual directions of the gradient and diffusion of carriers; the amplitude of the photocurrent depends not only on the typical parameters but on light direction and also gradient; determination of both effective lifetime of carriers and the bandgap by the Moss method is not valid for a semiconductor with a gradient of drift velocity; a photodetector with parameters reversibly controlled by an electric field is possible.