Implant activation in GaN Using an AlN cap

Gallium nitride (GaN) shows great promise as a wide band gap (WBG) semiconductor used in high power RF devices, and it also has the potential to be used for high power, high temperature applications. To date doping by ion implantation, necessary for Schottky diode guard rings and selectively implanted ohmic contact regions, has not been utilized due to the fact that the nitrogen evaporates preferentially at the temperatures required to activate the implants. In this work we describe the properties of a 'dual' AlN annealing cap characterized both before and after the sample is annealed, as well as the surface of the GaN film after selectively etching the cap off. The films are characterized using scanning electron microscopy (SEM), energy dispersive x-ray (EDAX) analysis, atomic force microscopy (ATM), and transmission electron microscopy (TEM). The activation of the implants was studied using a Hall effect and van der Pauw system, and the contact resistance of samples annealed at different temperatures was determined using TLM measurements.