CATHODOLUMINESCENCE OF WIRE-LIKE GAAS ALAS QUANTUM-WELL STRUCTURES GROWN ON SUBSTRATES PATTERNED WITH (001) MESA STRIPES

We describe cathodoluminescence (CL) spectroscopy and imaging studies of GaAs/AlAs quantum well (QW) structures and AlGaAs alloys grown by molecular beam epitaxy on GaAs (100) substrates patterned with mesa stripes along the [001] direction. GaAs wirelike structures were formed on these mesas due to the large diffusibility of Ga atoms from the {110} sidewalls to the (100) mesa-top plane. The spatial variation of the QW thickness and that of an AlGaAs alloy composition were investigated by carrying out CL measurements at low temperature. On the mesa-top region we found considerably large variations in the QW thickness and Al content, i.e., a 110% increase in the QW thickness and a 60% decrease in Al content, compared to the (100) bottom region. This is very useful for the fabrication of quantum-wire/box structures; thus, the use of the [001] mesa geometry is advantageous over other geometries.