CHARACTERIZATION OF AL0.4GA0.6AS GAAS APERIODIC SUPERLATTICES BY PHOTOLUMINESCENCE SPECTROSCOPY AT 2 K/

We present photoluminescence excitation (PLE) and picosecond time-reso lved photoluminescence (TRPL) results of an aperiodic superlattice (AS L) in static electric fields applied perpendicular to the heterojuncti on interfaces. The ASL consists of nine GaAs quantum wells separated b y Al0.4Ga0.6As barriers of varying thickness, such that electronic sta tes in individual QWs are in resonance in a finite electric field (sim ilar to 45 kV cm(-1)). We observed a drastic quenching of the photolum inescence intensity when the field is increased over a critical value, and a triple resonance of the heavy-hole exciton states originally co nfined in neighboring QWs, confirming the formation of an electron qua si-miniband. The TRPL and PLE spectra also suggest that the Coulomb-in teraction-induced redistribution of exciton oscillator strength is str ongly field-dependent at the resonant field. The ASL structure is demo nstrated to achieve control of both optical and transport properties i n desired electric fields. Theoretical calculations emphasis on the el ectron state resonance and the exciton radiative lifetime are performe d to understand the experimental data. (C) 1996 Academic Press Limited