Effects of growth temperature on electrical and structural properties of sputtered GaN films with a cermet target

GaN films have been deposited at 100-400 A degrees C substrate temperature on Si (100) and sapphire (0001) substrates by RF reactive sputtering in an (Ar + N-2) atmosphere. A (Ga + GaN) cermet target for sputtering was made by hot pressing the mixed powders of metallic Ga and ceramic GaN. The effects of substrate temperature on the GaN formation and its properties were investigated. The diffraction results showed that GaN films with a preferential (10-10) growth plane had a wurtzite crystalline structure. GaN films became smoother at higher substrate temperature. The Hall effect measurements showed the electron concentration and mobility were 1.04 x 10(18) cm(-3) and 7.1 cm(2) V-1 s(-1), respectively, for GaN deposited at 400 A degrees C. GaN films were tested for its thermal stability at 900 A degrees C in the N-2 atmosphere. Electrical properties slightly degraded after annealing. The smaller bandgap of similar to 3.0 eV is explained in terms of intrinsic defects and lattice distortion.