Miciro-raman spectroscopy and atomic force microscopy characterization of gallium nitride damaged by accelerated gallium ions

Gallium nitride on sapphire was characterized using AFM, SEM and micro-Raman spectroscopy after etching by a NOVA 200 FEI Focused Ion Beam (FIB). Various probe beam currents were used at a 30 kV acceleration voltage. The sidewall of the etched area was rougher and the roughness on the surface of the etched area increased when the probe beam current was increased. The intensity of the E-2(2) phonon of micro-Raman spectroscopy decreased when the probe beam current was increased from 10pA, 100 pA, 1 nA to 20 nA. Therefore, it is very important to control the FIB probe current to maximize the etch rate and minimize the damage induced by accelerated Gallium ions.