Photovoltaic effect in graded-band-gap layers with intrinsic type of conductivity

Peculiarities of photovoltaic effect (PVE) in graded-band- gap (GBG) layers with intrinsic type of conductivity and linear coordinate dependence of energy gap in the conditions of layer illumination by strongly absorbed monochromatic light are investigated theoretically. It is established that sign reversal of the photoEMF takes place on the spectral dependencies of PVE in the case when light is incident on the wide-gap of the layers. The dependence of PVE reversal point on the energy gap gradient and surface recombination velocities of charge carriers is analyzed. The photoEMF of GBG layers illuminated from narrow-gap side is shown to essentially exceed the photovoltage of uniform samples with the same energy gap as at narrow-gap side of GBG layers.