OPTICAL-PROPERTIES OF GAAS NANO-WHISKERS

Nanometer-size free-standing GaAs whiskers are fabricated by selective area growth based on reduced-pressure metal-organic vapor-phase epitaxy. Photoluminescence measurements of these GaAs whiskers show a spectral blue shift due to the two-dimensional quantum confinement of the carriers. The spectral blue shift is, however, much smaller than the lowest level energy expected by the square-potential confinement. This is due to a band-gap reduction induced by the charge separation caused by the existence of surface depletion potential, which is confirmed by surface passivation experiments using sulfur compounds. Furthermore, intense light emission is observed during carrier injection to the p-n junction formed in the GaAs whisker. The emitted light shows strong polarization anisotropy, which can be explained by the quantum confinement effect. These results indicate that nano-whiskers offer high-quality quantum wire structures, which can be applied to ultra-small opto-electronic devices.