Transient photovoltaic effects in anisotropic semiconductors

Abstract

A time-dependent ambipolar theory describing transient photovoltaic effects that occur in illuminated anisotropic semiconductors is discussed. The formalism is such that the theory may be used to describe transients in the transverse Dember, photopiezoresistance, and photomagnetoelectric effects. An anisotropic semiconductor having one surface uniformly illuminated with light of time-varying intensity is considered and general expressions for the short-circuit current and open-circuit photovoltage per unit length are obtained. Particular solutions for several different illuminations are included. Experiments undertaken to observe the transient photopiezoresistance effect in germanium, in which photovoltages as large as 1 V were recorded, are also described. A comparison between theory and experiment is included.