InGaAs/AlAsSb quantum wells (QWs) grown on InP substrates are recently attracting much attention for optical and electrical devices. We have reported the near-infrared intersubband transitions from this material system. We have also reported the ultra-fast absorption recovery of 0.69 ps and shown that this material system is suited for the ultra-high speed optical devices used in the optical communication network. However, the growth of this system is pretty difficult. We have already reported that As-interface termination procedure improve the QW property. The PL spectra of Sb-terminated QWs are broadened and red-shifted than that of the equivalent As-terminated version. In order to further improve the interface quality, we have introduced several mono-layers (MLs) of AlAs layer between InGaAs well and AlAsSb barrier.
We report here a detailed Raman scattering study of AlAsSb/InGaAs superlattices (SLs) and quantum-wells (QWs) grown by molecular beam epitaxy (MBE). The interface termination procedure and AlAs interface control layer are shown to influence a lot the Raman spectra: (1) the Sb-terminated SLs show clear InSb-related interface phonon at around 195 cm-1 and a weak broad peak at around 169 cm-1, while As-terminated SLs only show a weak broad peak, (2) when 4-MLs of AlAs layer is introduced, no features were observed below 200 cm-1, indicating well controlled interfaces, and (3) by inserting AlAs layer, AlAsSb band changed from 2-mode to single mode behavior. These results suggest that a Raman scattering is a sensitive microscopic probe of local disorder and clearly show that high quality interface is achieved in sample with AlAs layer.
This work was supported by New Energy and Industrial Technology Development Organization (NEDO) in the framework of Femtosecond Technology Project.

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1. Optical quality improvement of InGaAs/AlAs/AlAsSb coupled double quantum wells grown by molecular beam epitaxy