Selective wet-etching of InGaAs on InAlAs using adipic acid and its application to InAlAs/InGaAs HEMTs

Highly selective wet-etching of InGaAs on InAlAs was demonstrated using pH-controlled adipic acid, NH4OH and H2O2 solutions. A maximum selectivity of 250 was obtained by controlling the InGaAs and InAlAs etching mechanisms. By identifying the rate-determining steps for the etching of InAlAs and InGaAs, we found that the high selectivity is due to the difference in solubility between the oxide of InAlAs and that of InGaAs in the adipic acid solution. InAlAs/lnGaAs HEMTs fabricated in a 3'' diameter wafer by using this highly selective etching had a threshold voltage and a transconductance with standard deviations of 38 mV and 11 mS mm(-1), respectively.