The theory of a bulk photo-voltaic phenomenon in semi-conductors

Abstract

It is shown theoretically that for a photo-voltaic phenomenon in semi-conductors to exist neither the presence of localised potential barriers with rectifying properties at the contact of a semi-conductor with a metal (Mott's theory 1939) or at a p-n junction (Sosnowski, 1947) nor the presence of non-rectifying contacts (Dember's phenomenon, Lashkarev's theory 1948) is necessary. The case is considered that the illuminated part of the semi-conductor is sufficiently distant from both contacts so that these will not assert themselves; further, it is assumed that there are no localised potential barriers in the semi-conductor. Under these conditions a photo-voltage is produced in a semi-conductor if its conductivity varies throughout its length in such a way that in the dark it is different at the beginning and end of the illuminated part. For this type of “non-barrier and non-contact” photo-voltage we propose the name “bulk” photo-voltage. The underlying law of this phenomenon, the general procedure for calculating the photo-voltage, an approximation for weak illumination and the dependence on the intensity of illumination are derived and its physical aspects are discussed.