IMPROVED GAAS/ALAS MULTILAYER STRUCTURES GROWN BY MBE ON PATTERNED GAAS (100) SUBSTRATES WITH RIDGES ALONG THE [001] DIRECTION

GaAs/AlAs multilayer structures were grown by MBE on patterned GaAs (100) substrates with submicrometre-width ridges in conventional [011BAR] and new [001] directions, and their cross-sectional structures were investigated by TEM. On the [001] ridges, {110} side facets with very good morphology were formed on both sides of the (100) terrace, in contrast with the rather poor morphology of {311} A side facets for the conventional [011BAR] ridge case. GaAs quantum wire (QWR) structures (with a triangular cross section, 26 nm wide by 18 nm high) surrounded by very flat AlAs {110} side facets and a (100) plane were formed on the top of the (100) terrace on the [001] ridges. This indicates that the [001] ridge pattern is highly desirable for fabricating high-quality QWR structures. The migration length of Al atoms on the (100) plane during MBE growth at 570-degrees-C was determined for the first time to be 8 nm by TEM observation.