Abstract

Recently, considerable attention has been drawn to the novel electrooptical properties of semiconductor superlattices (SLs) under an electric field.^1-3 The resonant coupling of quantum wells (QWs) in a SL forms minibands from the discrete QW energy levels. When an electric level F is applied along the growth direction, this resonant coupling is reduced as the energy levels in consecutive QWs become misaligned by an energy qFd, where d is the SL period, and the eigenstates localize over a few adjacent QWs. This is called Wannier-Stark localization and gives rise to a change of absorption from that of a miniband profile to a sharp QW excitonic shape. An effective blue shift of the absorption edge is, therefore, predicted,¹ because the SL band gap is smaller than that of the isolated QW level by the half sum 1/2 (BW_e + BW_h) of the related conduction BW_e and valence BW_h miniband widths.

© 1990 Optical Society of America