Influence of mask material on the electrical properties of selective area epitaxy GaN microstructures

The authors have investigated the effect of dielectric (SiO2/SiNx) and metal (W) masks on impurity incorporation and electrical properties of selective area epitaxy (SAE) GaN microstructures. It is shown that SAE growths result in highly conductive n-type material. Carrier concentrations greater than metal-nonmetal transition level and low resistivity in the range of 0.18–0.29 mΩ cm were observed from Hall measurements for these structures. Two terminal current-voltage measurements showed a 40× increase in current for SAE GaN microstructure devices compared to that of conventional planar GaN devices. Secondary ion mass spectroscopy (SIMS) measurements of unintentional Si and O dopants in these structures showed dependency on the mask type. Similar dopant and carrier concentrations were obtained from SIMS and Hall data, indicating low compensation from acceptors in the SAE growths.