ELECTROREFLECTANCE INTENSITY FOR RESONANT COUPLING BETWEEN WANNIER-STARK LOCALIZATION STATES IN A GAAS ALAS SUPERLATTICE

We have measured the electric-field dependence of the electroreflectance intensities of the heavy-hole and light-hole exciton transitions associated with the first (n = 1) subbands in a GaAs (6.4 nm)/AlAs (0.9 nm) superlattice embedded in a p-i-n structure at 77 K. It is found that the electroreflectance intensities are highly sensitive probes to detect the resonant couplings between the Wannier-Stark localization states owing to the intensity reduction induced by the wave-function delocalization. We have clearly detected the various resonant couplings between the hole subbands, which have not been observed yet, in addition to those between the electron subbands. We have analyzed the electroreflectance-intensity change for the resonant coupling on the basis of the overlap integral between the electron and hole wave functions by using a transfer-matrix method with the Airy function.