THE DEVELOPMENT OF A HIGHLY SELECTIVE KI I-2/H2O/H2SO4 ETCHANT FOR THE SELECTIVE ETCHING OF AL0.3GA0.7AS OVER GAAS/

The selective etching of n-Al0.3Ga0.7As with respect to p(+)-GaAs is u seful for the fabrication of AlGaAs/GaAs heterojunction bipolar transi stors (HBTs). The KI/I-2/H2O/H2SO4 etching solution was found to be su perior to the KI/I-2/H2O solution in terms of selectivity. The selecti vity could be furthered improved by aging the etching solution for 3 d ays and by lowering the temperature from room temperature to the ice p oint. The best selectivity achieved was 330 with etch rates of 0.165 m u m/min and 0.0005 mu m/min for Al0.3Ga0.7As and GaAs respectively for a stabilized KI/I-2/H2O/H2SO4 at an etching temperature of 3 degrees C.