Citric Acid Etching of GaAs1 − x Sb x , Al0.5Ga0.5Sb , and InAs for Heterostructure Device Fabrication

Abstract

Citric acid/hydrogen peroxide at volume ratios from 0.2:1 to 20:1 was found to provide selective etching between , , , and various III–V semiconductor materials for use in new and based heterostructure transistors and optoelectronic devices. By choosing different concentration volume ratios of citric acid to hydrogen peroxide , highly selective as well as uniform (nonselective) etching regions were found to exist in these material systems. Etchant selectivities greater than 50 were found for most combinations of the III–V semiconductor materials under investigation, with selectivities of over 100 measured for and material combinations, and with selectivities of over 3850 calculated for to 13,650 for . The highest overall etch rates were measured for and the lowest etch rates were found for . The etch rate for the materials systematically decreased from the highest etch rate for the smallest Sb mole fraction examined of to the lowest etch rate for . The dramatic change in etch rate with citric acid/hydrogen peroxide volume ratio previously observed for the material system was also observed for , but this effect was not seen in higher Sb mole fraction alloys of examined. and were found to have very low etch rates with this etchant system at all volume ratios, making both materials suitable as an etch stop layer for simplified processing in device fabrication. 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.