PHOTOLUMINESCENCE DETECTION OF THE X-ELECTRON RESONANCE IN A GAAS ALAS TYPE-II SUPERLATTICE/

We report on a photoluminescence study of the X-electron resonance in a GaAs (3.4 nm)/AlAs (5.1 nm) type-II superlattice embedded in an n-i- n structure. We have measured the photoluminescence spectra of the typ e-II exciton consisting of the first X-z (X(z)1) electron and the Gamm a 1 heavy hole, which are confined in the AlAs and GaAs layers, respec tively, as a function of an applied bias (electric field). We find tha t the electric-field dependence of the type-II photoluminescence inten sity reflects various X-electron resonances such as X(z)1-X-xy 1, X(z) 1-X(z)2, and optical-phonon-assisted X(z)1-X(xy)1 The resonance condit ions are discussed from the X-electron energies calculated in the fram ework of an effective-mass approximation taking account of lattice-mis match strain and electric-field effects. In addition, it is demonstrat ed from the photocurrent-bias-voltage characteristics that the X-elect ron resonance improves the carrier sweep-out through the superlattice.