ELECTROREFLECTANCE DETECTION OF RESONANT COUPLING BETWEEN WANNIER-STARK LOCALIZATION STATES IN A GAAS/ALAS SUPERLATTICE

We report electroreflectance (ER) detection of the resonant coupling between the Wannier-Stark localization states in a GaAs(6.4 nm)/AlAs(0.9 nm) superlattice. We find that the ER line shapes of the heavy-hole and light-hole exciton transitions associated with the first (n = 1) subbands clearly exhibit splitting features with anticrossing behaviors, resulting from the second- and third-nearest-neighbor resonant couplings between the n = 1 and n = 2 electron subbands, and that the intensities are remarkably reduced in the resonant condition owing to the delocalization of the electron wave function. In addition, it is demonstrated that ER spectroscopy is much more sensitive to detect the resonant coupling than photocurrent spectroscopy. We analyze the ER results of the resonant coupling by using a transfer-matrix method with Airy functions.