INTERBAND OPTICAL-TRANSITION SPECTRA IN GAAS QUANTUM WIRES WITH RECTANGULAR CROSS-SECTIONS

Interband optical transition spectra of rectangular GaAs quantum wires (QWR's) of various cross-sectional sizes are experimentally and theor etically studied. High-quality GaAs QWR's with lateral sizes below 20 nm are formed in AlAs trench structures with (110) vertical sidewalls by using metal-organic chemical vapor deposition. Polarization-depende nt photoluminescence excitation (PLE) spectra in the QWR's clearly exh ibit absorption peaks corresponding to optical transitions between qua ntized one-dimensional conduction and valence subbands. It is found th at transition strengths and polarization anisotropies in the lowest- a nd higher-energy PLE peaks significantly vary, depending on the cross- sectional shape of the rectangular wires. The polarization-dependent i nterband transition matric; elements and the detailed absorption spect ra are calculated by a multiband effective-mass theory considering hea vy-hole and light-hole subband mixing. The theoretical results clarify tile physical origin of observed PLE peak and explain the strong depe ndence of interband transition properties on the cross-sectional ratio of QWR's.