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

• Free-standing GaAs/AlGaAs single quantum well (SQW) and InGaAs/GaAs bilayer microtubes have been fabricated by photolithography and chemical etching.
• A single PL peak at 824 nm and 870 nm was observed for SQW and bilayer microtubes, in which quantum-confinement-effect (QCE)-induced blue-shift (~46 nm) of GaAs PL peaks could be seen.
• Raman measurements demonstrated the two-mode behavior of Al0.3Ga0.7As barrier in SQW for the first time and the red shifting of LO to lower frequencies reflected the compressive strain decrease.

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 (~824 nm) and bulk GaAs (~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 (~46 nm) of GaAs PL peaks. The spectral red-shift (~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 (~10 cm−1) when compared with SQW planar, reflecting the compressive strain decreases.