Optical studies of free-standing GaAs/AlGaAs single quantum well (SQW) microtubes: A comparison with InGaAs/GaAs bilayer microtubes

摘要

Optical properties of free-standing GaAs/AlGaAs single quantum well (SQW) microtubes have been investigated by room-temperature micro-photoluminescence (PL) and Raman measurements, followed by the detailed comparison with the corresponding properties of InGaAs/GaAs bilayer microtubes. Single peaks originating from GaAs SQW (similar to 824 nm) and bulk GaAs (similar to 870 nm) were observed in PL spectra of free-standing SQW and bilayer microtubes, respectively, which clearly shows the quantum-confinement effect (QCE)-induced blue shift (similar to 46 nm) of GaAs PL peaks. The spectral red-shift (similar to 12 nm) of SQW PL peak due to strain release was confirmed after the as-grown planar rolled up into microtube. For Raman spectra, both GaAs-like and AlAs-like LO phonons of Al0.3Ga0.7As barrier which demonstrated the two-mode behavior were observed for SQW microtubes. Meanwhile, all LO phonon modes of SQW microtube were obviously red-shifted to lower frequencies (similar to 10 cm(-1)) when compared with SQW planar, reflecting the compressive strain decreases. (C) 2015 Elsevier B.V. All rights reserved.