A COMPARISON OF THE SELECTIVE ETCHING CHARACTERISTICS OF CONVENTIONALAND LOW-TEMPERATURE-GROWN GAAS OVER ALAS BY VARIOUS ETCHING SOLUTIONS

In this work we report the selective etching characteristics of GaAs g rown by molecular beam epitaxy oi er AlAs etch-stop layer in four etch ing solutions. We show that these solutions, which are commonly used f or selective etching of GaAs grown at the conventional temperature of 600 degrees C (HT GaAs) are also effective for low-temperature GaAs gr own at 230 degrees C with annealing at 600 degrees C (a-LT GaAs) and l ow-temperature-grown GaAs without annealing (LT GaAs). In these soluti ons, the etching rates of LT GaAs and a-LT GaAs are lower than that of HT GaAs and hence the selectivities of LT GaAs and a-LT GaAs over AlA s are lower than that of HT GaAs over AlAs. The succinic acid/H2O2 sol ution with pH = 4.2 was found to be the best selective etchant. Furthe rmore, we observed, for the first time, that the AlAs etch-stop layer tended to fail at the periphery of the etched windows, resulting in vo id formation if the etching was excessive. It took a longer time for t his to happen in the succinic acid/H2O2 solution than in other solutio ns investigated.