CONTROLLED ANODIC-OXIDATION FOR HIGH-PRECISION ETCH DEPTH IN ALGAAS ILL-V SEMICONDUCTOR STRUCTURES

Controlled anodic oxidation far achieving a better control of etch dep th in AlGaAs semiconductor structures is studied. The rates of materia l consumption and oxide thickness growth for p(++)-GaAs and p-Al(0.38) G(0.62)As are given for the citric acid/glycol/water electrolyte. The etch profiles for GaAs/Al0.45Ga0.65As and GaAs/Al0.60Ga0.40As layer se quences in laser diode structures are presented. The underetch is rath er high and depends on oxidation conditions (constant voltage or const ant current). The profile obtained is very rough for constant voltage oxidation and much better when using constant current conditions. The latter also improves the uniformity of oxide growth. The etch rate of the anodic oxide in diluted HCl is much larger for GaAs than for AlGaA s.