Selective wet etching of Al0.7Ga0.3As layer in concentrated HCl solution for peeling off GaAs microtips

Selective wet etching of an Al0.7Ga0.3As sacrificial layer, sandwiched between two GaAs layers, at different HCl concentrations and temperatures has been investigated. This technique can be used in peeling off GaAs microtips for scanning near-field optical microscopy. The results show that the etching rate remains almost constant in a large range of etching length for the concentrated HCl etching of Al0.7Ga0.3As at a certain temperature. However, the etching rates increase very quickly for both Al0.7Ga0.3As and GaAs as the etching temperature increasing. Furthermore, the concentrated HCl at 0 °C is the optimal condition for selective wet etching of Al0.7Ga0.3As, at which the etching rate is about 0.5 μm/min for Al0.7Ga0.3As, but close to 0 μm/min for GaAs. Finally, the GaAs microtip, grown on the GaAs/Al0.7Ga0.3As/GaAs sandwich structure, is peeled off by concentrated HCl selective etching of Al0.7Ga0.3As layer at 0 °C. Scanning electron microscopy image demonstrates that the GaAs microtip can be successfully removed without damage by the above-mentioned method.