High-density quantum wires naturally formed on (7 7 5)B-oriented GaAs substrates by molecular beam epitaxy

Abstract

GaAs ( GaAs ) 2 ( AlAs ) 2 quantum wires (QWRs) were naturally formed 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-oriented GaAs substrates by molecular beam epitaxy. The QWRs were formed side by side with an extremely high density of 8 × 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 × 2 nm 2 , showed a strong polarization dependence (the polarization degree P ≡ [ (I ∥ − I ⊥ ) (I ∥ + I ⊥ ) ] = 0.21 ). The polarization degree is about twice as large as that of the previous 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.