High Conductivity Gan Grown By Reactive Sputtering

Single phase, epitaxial GaN films have been grown at 700 degrees C on c-sapphire by rf magnetron sputtering using a GaAs target, with 100 % and 10 % N-2 in Ar-N-2 atmosphere. High resolution XRD measurements reveal significant differences in the strain present in the two films. Electrical measurements show low resistivity similar to 2 x 10(-3) Omega-cm for the film grown with 10 % N-2, compared to the high resistivity (greater than or similar to 10(5) Omega-cm) of the film grown with 100 % N-2 in sputtering atmosphere. Optical studies reveal significant difference in band gap of the two films and free carrier features in NIR due to the high electron concentration of 1.2 x 10(20) cm(-3) in the film grown with 10 % N-2. XPS studies reveal the absence of As but presence of similar levels of oxygen impurity in the two films. The film grown with 10 % N-2 shows much smaller N/Ga ratio and the presence of uncoordinated Ga, indicating that nitrogen vacancies are likely to be responsible for its high conductivity.