Optical and structural characterization of InGaAs/AlAsSb quantumwells grown by molecular beam epitaxy

摘要

We report here a photoluminescence (PL), secondary ion massspectrometry (SIMS), and Fourier transform infrared spectroscopy (FTIR)study of highly Si-doped InGaAs/AlAsSb quantum wells (QWs) that arelattice-matched to InP substrates grown by molecular beam epitaxy (MBE).It is found that PL line-shape degradation caused by high Si doping tothe upper (surface side) AlAsSb barrier can be controlled by insertingan undoped AlAsSb spacer layer. However, when doped to the lower(substrate side) AlAsSb barrier, the broadening of the spectraindicating degradation of the interface, found to be unavoidable evenwith a 10-nm spacer layer. SIMS depth profiles confirm the out-diffusionof In and Ga from the InGaAs well to the AlAsSb barriers and Alincorporation into the InGaAs well. This group-III speciesinterdiffusion combined with the exchange reaction between As and Sb areconfirmed to be the origin of the extraordinarily broad PL spectra. Wealso report the short wavelength inter-subband transitions rangingbetween 1.35 μm to 2.0 μm from coupled double quantum wellstructures. However, as is expected from PL and SIMS results, highdoping shifts intersubband transition peaks toward longer wavelengths