I would like to remove P-type metal contact on GaAs/GaAlAs edge emitting laser (EEL) to do Photo-luminescence study next.Wet etch is preferred.

Since there is a SiO2 isolation layer underneath the P-type metals (except for the ridge region, where P -type metal is in direct contact with P++ GaAs), the P-type metal contact should be lifted off after SiO2 etching. However, the commonly used SiO2 wet etch chemistry (buffered NH4F-HF; diluted HF; acetic acid-NH4F, etc.) tends to attack Al and Ga in the junction region and damages the narrow ridge wave-guide structure.

what is the best wet etch chemistry to remove SiO2 WITHOUT attack AlGaAs?

Thanks