AlAs etch-stop layers for InGaAlAs/InP heterostructure devices and circuits

Wet chemical etching solutions were developed that allow the selective etching of InP lattice-matched InGaAs and InAlAs compounds using thin pseudomorphic AlAs layers as etch stop. Several dicarboxylic acids were found that allow the etching of indium compounds. The best results were obtained for etchants consisting of succinic acid, ammonia, and hydrogen peroxide. The etch rate in In/sub 0.53/Ga/sub 0.47/As is found to be over 1000 times the etch rate of AlAs, while the etch rate of In/sub 0.52/Ga/sub 0.48/As is over 500 times that of the AlAs. The dependences of the succinic acid based etch on pH and hydrogen concentration were also studied. Buffered HF can be used to remove the AlAs stop layer, while it does not etch InGaAlAs to any significant degree.>