LIQUID-PHASE EPITAXIAL REGROWTH ON SULFIDE-PASSIVATED GA1-XALXAS

We demonstrate that Na2S passivation allows liquid phase epitaxial regrowth of Ga0.5Al0.5As upon Ga1-xAlxAs (0.3 less-than-or-equal-to x less-than-or-equal-to 0.8) air exposure. Large aluminum concentrations require concentrated (2.4 M) sulfide solutions. We have also studied the Ga1-xAlxAs etching rate by Na2S. For large sulfide concentrations or small aluminum concentrations, the etching process stops after some time. These two phenomena are correlated because both of them require the presence on the surface of a stable protective layer. This can be understood by assuming the existence at the surface of two competing mechanisms: etching and passivation.