Transferring of GaAs microtips using selective wet etching Al0.7Ga0.3As sacrificial layer

GaAs pyramidal microtips were successfully transferred from GaAs substrate to target wafer by a simple technique, i.e., selective wet etching off AlGaAs sacrificial layer. A GaAs/Al_0.7Ga_0.3As/GaAs sandwich structure is firstly formed on GaAs (0 0 1) substrate by metalorganic chemical vapor deposition, and then GaAs pyramidal microtips are grown on the sandwich structure using selective liquid-phase epitaxy. The GaAs microtips are removed from the sandwich structure by selective wet etching Al_0.7Ga_0.3As layer using concentrated HCl solution. Finally, the tips are glued onto the target wafer by a negative photoresist. During this transfer process the tips are completely encapsulated in a positive photoresist to protect against attack. Scanning electron microscopy images show that GaAs tips can be successfully transferred without any damage by this technique. The achievement reported here represents a significant step towards the application of scanning near-field optical microscopy.