High selective etching GaAs/Al < inf > 0.3 < /inf > Ga < inf > 0.7 < /inf > As for the high electron mobility transistor (HEMT) applications using citric buffer solution

Abstract

High selective wet etching of GaAs on Al0.3Ga0.7As can be realized using citric buffer (citric acid/H2O2/H2O) solution. The selectivity of GaAs to Al0.3Ga0.7As was as high as 264 at 23 °C by optimizing the pH and citric acid/hydrogen peroxide ratio having the etch rate of GaAs is 18.08 Å/s and etch rate of Al0.3Ga0.7As is 0.0685 Å/s at a pH of 2.32. The etch stop mechanism is attributed to the formation of dense oxide Al2O3 on Al0.3Ga0.7As. This finds applications in high electron mobility transistors (HEMT) gate recess processes, no obvious drain current decrease can be perceived even after 12 min over etching.