Submicron Raman and photoluminescence topography of InAs/Al(Ga)As quantum dots structures

• Published in: Applied surface science 2012-11, Vol.260, p.47-50
• Main Authors: Kolomys, O.F., Strelchuk, V.V., Shamirzaev, T.S., Romanyuk, A.S., Tronc, P.
• Format: Article
• Language: English
• Subjects: InAs quantum dots; Intermixing; Micro-Raman scattering; Photoluminescence
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.02.149

► Exciton recombination in an ensemble of indirect/direct band-gap (In,Al)As/AlAs QDs with type-I band alignment is studied. ► Resonant Raman scattering was applied for evaluation of composition at various depths InAlAs/AlAs QDs sandwich structures. ► Depth distribution of composition in In(Ga,Al)As alloy layers explained by strain-driven enhanced interdiffusion. Two-period structures with and without vertical coupling between indirect and direct bandgap InAs quantum dots (QDs) both with type I band alignment, grown by molecular-beam epitaxy, were investigated by confocal Raman and photoluminescence (PL) microspectroscopy. The observed blue shift of PL band of the indirect (direct) bandgap QD by 20 (80)meV with decrease of thickness of Ga(Al)As intermediate layer between two InAs QD layers from 30 to 8nm is considered as caused by increase of elastic strains (decrease of QDs sizes) in QD layers and by coupling between QDs electronic states. Scanning confocal resonant Raman microspectroscopy was applied for non-destructive evaluation of composition at various depths along the thickness of vertical coupling of the upper InAs/AlGaAs and lower InAs/AlAs QDs layers of the sandwich structures. Based on the analysis of determined from the in-depth Raman spectra optical phonons frequencies, the depth distribution of composition in InAlAs and GaAlAs alloy layers formed as a result of strain-driven enhanced interdiffusion was determined.