Limitations to the Bandgap-Selective Photoelectrochemical Etching of GaAs/Al x Ga 1−x as Heterostructures

We have used the wet photoelectrochemical (PEC) etch process to demonstrate the selective removal of low aluminum (Al) mole-fraction Al x Ga 1−x As layers from those with higher Al mole-fraction. High etch selectivity was found for δ x as low as 0.05, but was found to decrease as the incident photon energy approached the energy bandgap of the desired stop-layer. The ultimate selectivity of one layer from an underlying layer was affected not only by differences in material composition, but also by the sequencing of the layers within the structure.