Homogeneous nucleation of opposite moving dipole domains and current self-oscillations in undoped photoexcited superlattices

A model for charge transport in undoped photoexcited semiconductor superlattices with field-dependent recombination is proposed and analyzed. Under dc voltage bias and large photoexcitation, there appear self-sustained oscillations of the current due to repeated homogeneous nucleation of a number of charge dipole waves inside the sample. Different from the case of a constant recombination coefficient, nucleated dipole waves may split in two oppositely moving dipoles.