Photocapacitance effect at low temperatures in a unipolar MIS capacitor with a semiconductor electrode doped with two different acceptor impurities

Abstract

The photocapacitance effect at low temperatures in a unipolar MIS capacitor with a semiconductor electrode doped with two types of acceptor impurities characterized by different ionization energies E ia (deep-level acceptor) and E ib (shallow-level acceptor) is examined theoretically. It is shown that the photocapacitance response of such a capacitor arises in a relatively narrow range of bias voltages. The maximum of the response at a constant bias depends on the temperature as exp(E ia /kT). An infinite increase in the photocapacitance response is related to the singularity that appears with decreasing temperature in the bias-voltage dependence of the ionized acceptor concentration. The capacitance and photocapacitance characteristics for a structure with a silicon electrode doped with In and B are calculated.