ETCH RATES AND SELECTIVITIES OF CITRIC ACID/HYDROGEN PEROXIDE ON GAAS, AL0.3GA0.7AS, IN0.2GA0.8AS, IN0.53GA0.47AS, IN0.52AL0.48AS, AND INP

Etching studies involving citric acid/hydrogen peroxide (C6H8O7:H2O2) 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 GaAs and InP 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 ((chi)C6H8O7:1H2O2). Etchant selectivities, defined as a ratio of the etch rates, for the GaAs-based materials were measured to be as high as 116 for GaAs/As0.3Ga0.7As and 120 for In0.2Ga0.8As/Al0.3Ga0.7As. In addition, the InP system had selectivities of approximately 60 and 100 for In0.53Ga0.47As/In0.52Al0.48As and In0.52Al0.48As/InP, with the highest selectivity of 473 found for In0.53Ga0.47As/InP. The citric acid/hydrogen peroxide system can be used as a stop etch for InP-based devices, as InP 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.