The development of a highly selective KI/I2/H2O/H2SO4 etchant for the selective etching of Al0.3Ga0.7As over GaAs

Abstract

The selective etching of n-Al0.3Ga0.7As with respect to p+-GaAs is useful for the fabrication of AlGaAs/GaAs heterojunction bipolar transistors (HBTs). The KI/I2/H2O/H2SO4 etching solution was found to be superior to the KI/I2/H2 O solution in terms of selectivity. The selectivity could be furthered improved by aging the etching solution for 3 days and by lowering the temperature from room temperature to the ice point. The best selectivity achieved was 330 with etch rates of 0.165 μm/min and 0.0005 μm/min for Al0.3Ga0.7As and GaAs respectively for a stabilized KI/I2/H2O/H2SO4 at an etching temperature of 3° C.