DIFFUSION-LIMITED ETCHING OF P-GAAS IN NAOH-NA2EDTA SOLUTIONS

Mass-transport-limited etching of p-type GaAs using sodium hydroxide (NaOH) and disodium ethylenediamine tetraacetate (Na2EDTA) has been studied. Isotropic etching of (100)-oriented p-type GaAs was obtained for pH values between 8 and 13, and uniform etch rates were obtained over 0.05-0.25 mum/min with an unstirred solution. Etching cycles consisted of anodic oxidation for 20-40 s followed by oxide removal when the potential was set just negative of the rest potential for 5-10 s. The diffusion-limited currents were found to be relatively insensitive both to changes in oxidizing voltage and to variations in the hole concentration in the GaAs. Etching in the mass-transport limited regime was found to be a convenient and useful approach when profiling the GaAs hole concentration with electrochemical capacitance-voltage measurements.