High-density GaAs/(GaAs)(2)(AlAs)(2) quantum wires naturally formed on (775)B-oriented GaAs substrates by molecular beam epitaxy

GaAs/(GaAs)(2)(AlAs)(2) quantum wires (QWRs) were naturally firmed in a thin GaAs/(GaAs)(2)(AlAs)(2) quantum well (QW) with a regularly corrugated AlAs/GaAs upper interface (a period of 12 nm) and a flat GaAs/AlAs lower interface grown on (7 7 5)B-orienred GNAs substrates by molecular beam epitaxy. The QWRs were formed side by side with an extremely high density elf 8 x 10(5) QWRs/cm, which is the same to that of the previous GaAs/AlAs QWRs grown on the (7 7 5)B substrate (the highest density of QWRs ever reported [8]). A photoluminescence from the QWRs formed in the QW with an average well width (L-w) of 2.1 nm, which have a cross section of about 12 x 2 nm(2), showed a strong polarization dependence (the polarization degree P drop [(I parallel to - I perpendicular to)/(I parallel to + I perpendicular to)] = 0.21). The polarization degree is about twice as large as that of the precious GaAs/AlAs QWRs with an average L-w of 3.3 nm grown on the (7 7 5)B substrate. This improvement of the polarization degree is mainly due to the further reduced QW width, which results in an improved one-dimensional confinement of carriers in the present QWRs.