Abstract
Etching studies involving citric acid/hydrogen peroxide 
at volume ratios from 0.5:1 to 50:1 were found to provide good selective etching of various III‐V semiconductor materials grown on 
and 
substrates using molecular beam epitaxy. Both selective and uniform (nonselective) etching regions were found between these material systems by choosing different concentration volume ratios of citric acid/hydrogen peroxide 
. Etchant selectivities, defined as a ratio of the etch rates, for the 
materials were measured to be as high as 116 for
and 120 for 
. In addition, the 
system had selectivities of approximately 60 and 100 for 
and 
, with the highest selectivity of 473 found for 
. The citric acid/hydrogen peroxide system can be used as a stop etch for 
devices, as 
is virtually unaffected by this etchant. Finally, citric acid/hydrogen peroxide can be used to preferentially etch these materials through a photoresist mask, since it does not erode photoresist at any volume ratio.