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 degrees C for NH(3) doses starting from 90 s. Atomic layer deposition temperature window was observed from 185 to similar to 385 degrees C. Deposition rate, which is constant at similar to 0.51 angstrom/cycle within the temperature range of 250 - 350 degrees C, increased slightly as the temperature decreased to 185 degrees C. In the bulk film, concentrations of Ga, N, and O were constant at similar to 36.6, similar to 43.9, and similar to 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. (C) 2012 American Vacuum Society. [DOI: 10.1116/1.3664102]