Selective wet etching of a GaAsAlxGa1−xAs heterostructure with citric acid-hydrogen peroxide solutions for pseudomorphic GaAs/AlxGa1−xAs/InyGa1−yAs heterojunction field effect transister fabrication

The selective wet etching characteristics of GaAsAlxGa1−xAs1−x systems in citric acid-hydrogen peroxide solution have been studied for x = 0.15, x = 0.2 and x = 0.3 respectively. A 4:1 ratio of citric acid (50% by weight)-H2O2 solution was found to be a better selective etchant than the more commonly used NH4OHH2O2 solutions. The selectivity obtained was more than 110 for x = 0.3. The simple and reliable selective wet etchant was applied to the gate recess etching in the fabrication of pseudomorphic GaAs/AlxGa1−xAs/InyGa1−yAs heterojunction field effect transistors.