MOCVD METHODS FOR FABRICATING GAAS QUANTUM WIRES AND QUANTUM DOTS

Semiconductor low-dimensional structures such as quantum wires and quantum dots fabricated by metalorganic chemical vapor deposition (MOCVD) are reported. GaAs/AlAs quantum wire arrays including fractional-layer superlattices were grown on (001) GaAs vicinal surfaces. Uniform lateral superlattices were observed by transmission electron microscopy. However, polarization-dependent photoluminescence and the optical absorption spectra suggest that significant alloying occurs in AlAs/GaAs vertical interfaces. GaAs tetrahedral quantum dots buried in AlGaAs were also fabricated on a SiO2 masked (111)B GaAs substrate partially etched to a triangular shape. First, AlGaAs truncated tetrahedral structures with three {110} facets were grown on GaAs triangular areas. Next, GaAs dot structures were sequentially grown on top of the AlGaAs truncated tetrahedron. Finally, AlGaAs was over-grown on {110} sidewall facets with a different growth condition. We observed large quantum size effects for about 100 nm TQD in low temperature photoluminescence, which is in good agreement with calculations.