Subbands and excitons in a quantum well in an electric field

Abstract

The effects of an electric field on the subbands and excitons in a quantum well are discussed with the use of an infinite-potential-barrier model. It is shown that for increasing electric fields the energy of the lowest subband state becomes lower, while that of higher subband states becomes slightly higher initially and then decreases. This behavior of the subbands affects excitonic properties for which a model variational calculation of the energy and the oscillator strength is performed. It is found that (1) the exciton energy shift depends strongly on the electron and hole subbands with which the excitons are associated and that (2) for large electric fields, oscillator strengths for usually forbidden excitons with different electron and hole subband indices become similar in magnitude to those for allowed excitons. These results agree well with the main features of optical absorption experiments.