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 usin g pH-controlled adipic acid, NH4OH and H2O2 solutions. A maximum selec tivity of 250 was obtained by controlling the InGaAs and InAlAs etchin g mechanisms. By identifying the rate-determining steps for the etchin g of InAlAs and InGaAs, we found that the high selectivity is due to t he difference in solubility between the oxide of InAlAs and that of In GaAs in the adipic acid solution. InAlAs/lnGaAs HEMTs fabricated in a 3'' diameter wafer by using this highly selective etching had a thresh old voltage and a transconductance with standard deviations of 38 mV a nd 11 mS mm(-1), respectively.