PACS 81.05. Ea, 81.15.Hi Application of migration-enhanced deposition sequence to area selective growth of GaAs and other III -V compound semiconductors makes it possible to achieve well-defined area selective growth even using solid source molecular beam epitaxy. Successful growth of small disks and other structures has been performed on SiO 2 masked (111)A and (111)B substrates at temperatures around 590 °C. General rule for facets formation suggests that the facet angle is quite sensitive to the V/III flax ratio as well as the substrate orientation. To create vertical {110} facets around the structures at relatively low V/III flux ratios, (111)A substrates is much more preferable to (111)B substrate. However, high density of hillocks emerges on the structures grown on (111)A substrate. It is found that the hillocks are caused by the stacking faults. The density of hillocks has been dramatically reduced by depositing As in the Ga deposition period.

We have carried out area-selective epitaxial growth of GaAs on GaAs(111)A substrates using migration-enhanced epitaxy and have investigated the pyramidal hillocks formed on the grown surface. Scanning electron microscopy and atomic force microscopy observations indicate that these hillocks can be classified into two types: hillocks with small top plateaus and those with large plateaus. Investigations on the growth condition dependence of surface morphology and plan-view transmission electron microscopy observation have revealed that both types of hillocks are caused by stacking faults. Hillock cores are found to be stacking fault tetrahedra, whose formation processes result in two types of hillocks. Additionally, we have succeeded in improving the surface flatness by increasing the surface arsenic pressure during growth.

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We have carried out area-selective epitaxy of GaAs microdisk structures on a SiO2-masked GaAs substrate by migration-enhanced epitaxy. We have successfully grown “damage-free” disks at 590 °C. It is found that, for the structures grown on (111)B substrates, the facets surrounding the disks are controlled by the V/III beam equivalent pressure ratio. This characteristic is caused by the reduced growth rate in the [111]B direction under high V/III ratios. Using an optimized growth condition, uniform hexagonal GaAs disks surrounded by six vertical {110} facets and a flat (111)B top are grown. The microdisks grown on (001) substrates, however, show no flat-top structures, regardless of the V/III ratio, probably due to the fact that the growth rate in the (001) direction is not sensitive to the V/III ratio. In the latter case, square-pyramidal structures surrounded by four inclined {011} facets are obtained.