Selective area formation of arsenic oxide-rich octahedral microcrystals during photochemical etching of n-type GaAs

These crystal-like octahedral structures grow to various sizes ranging from 5 micron to 100 micron depending on the time of etch. The structures have also been observed to form only in illuminated regions that have a large enough area.

Substrate quality also affects the nature of microcrystal formation. Individual microcrystals were observed for prime grade wafers while a network of microcrystalline features was observed for mechanical grade wafers.