Optically-induced switching, tunneling and relaxation processes in aluminum arsenide/gallium arsenide triple-barrier resonant tunneling diodes

AlAs/GaAs triple-barrier resonant tunneling structures (TB RTS), consisting of a wide and a narrow GaAs quantum well (WW and NW) defined by three AlAs barriers, were investigated by optical spectroscopy.; A bistable p-i-n TB RTS was studied to determine its response time as a fast-switching photonic component. Optical perturbation by a laser-pulse induces switching of the device between the two states. An upper limit for the switching time of 400 ps was determined by time-resolved electroluminescence using the single-photon correlation techniques.; Photoluminescence (PL) measurements were employed to study the optical- and trans-port properties of a unipolar n-type TB RTS. Several higher-exciton transitions were observed. At each of the three current resonances the nature of the triple-level alignment was evidenced by the higher-exciton PL measurements. Electron intersubband relaxation times are shown to be shorter than the tunneling times, resulting in electron populations in higher subband. These electrons are not thermalized and "hot" electron tunneling is a significant current component. The existence of the electron-dressed exciton and of phonon-assisted tunneling processes were also demonstrated by PL measurements.; Resonant Raman scattering (RRS) of a single quantum well was used to probe phonon modes and electron-phonon interactions in the same n-type TB RTS. Three even LO phonon modes in the NW were observed due to coupling with the NW hh1-exciton. Very large Raman efficiencies were observed in outgoing resonance, resulting from double resonance conditions. RRS of phonon modes in the WW was observed under an electric field and a large field-induced enhancement was obtained because of Frohlich interaction involving the e2-hh1 higher-exciton in this quantum well.