Atomic layer deposition of GaN at low temperatures
The authors report on the self-limiting growth of GaN thin films at low temperatures. Films were deposited on Si substrates by plasma-enhanced atomic layer deposition using trimethylgallium (TMG) and ammonia (NH 3) as the group-III and -V precursors, respectively. GaN deposition rate saturated at 185 C for NH 3 doses starting from 90 s. Atomic layer deposition temperature window was observed from 185 to ∼385 C. Deposition rate, which is constant at ∼0.51 cycle within the temperature range of 250 - 350 C, increased slightly as the temperature decreased to 185 C. In the bulk film, concentrations of Ga, N, and O were constant at ∼36.6, ∼43.9, and ∼19.5 at. , respectively. C was detected only at the surface and no C impurities were found in the bulk film. High oxygen concentration in films was attributed to the oxygen impurities present in group-V precursor. High-resolution transmission electron microscopy studies revealed a microstructure consisting of small crystallites dispersed in an amorphous matrix. © 2012 American Vacuum Society.