Smith Gw

Photoluminescence and photoluminescence excitation studies on GaAs/AlAs short period superlattices near the direct/indirect crossover

A photoluminescence (PL) and PL excitation (PLE) investigation of GaAs/AlAs superlattices near the direct to indirect gap, type I to type II superlattice crossover is reported. The nature of the phonon coupling, the magnitude of the Stokes’ shifts between PL and PLE, and the dependence of the PL spectra on hydrostatic pressure are studied. From these results a change of the GaAs width (d) by just 1 monolayer (ML) from 12 to 11 ML is shown to cover the range from near coincidence of the GaAs (Γ) and AlAs (X) conduction band minima, but with type I, direct gap character dominant at d=12 ML, to clearly indirect gap, type II behavior at d=11 ML.

Optical Spectroscopy of Double Barrier Resonant Tunneling Structures

Recent applications of optical spectroscopy to the study of double barrier resonant tunneling structures are discussed. Particular topics emphasized are the determination of charge build up in the quantum well active region on resonance, determination of the nature of the tunneling processes and the detection of electroluminescence emission resulting from impact ionisation in double barrier structures.

Resonant Raman scattering in GaAs/AlAs quantum wells

Resonant Raman studies of type II GaAs/AlAs quantum wells, using excitation into the forbidden Gamma -X transition, have revealed new Raman lines that are close to X-point zone-edge acoustic and optic phonons of GaAs and AlAs.