Peelable GaAs mircotips grown by one-step selective liquid phase epitaxy

We present a simple one-step selective liquid-phase epitaxy (LPE) method to prepare peelable GaAs pyramidal microtips for compact scanning near-field optical microscopy (SNOM). A high Al content AlGaAs thin layer, as an etching sacrificial layer, is firstly selectively grown in periodic square windows of SiO2 mask deposited on GaAs substrate, and then GaAs is grown on the AlGaAs layer to automatically form peelable pyramidal microtip array. After the growth of the microtip array, the wafer is immersed into concentrated HCl solution at ice-point temperature to selectively etch off the AlGaAs layer and separate the microtips from the substrate. Scanning electron microscopy (SEM) images show that the microtips grown and peeled by this method are similarly high in quality with the peelable microtips prepared by two-step growth process we have reported before, but the one-step growth process is simpler and cheaper.