RF plasma sources for III-nitrides growth: influence of operating conditions and device geometry on active species production and InN film properties

The optical emission from an RF inductively coupled plasma source has been monitored at various flow rates and RF powers in the spectral range of 500-900 nm. It was found that low powers and high flow rates resulted in emission from the 1st-positive series of excited molecular nitrogen dominating the spectrum relative to atomic nitrogen. Growth of InN on GaN showed improved electrical properties when the molecular species dominated the spectrum. In contrast, growth of InN on (111) yttrium stabilised zirconia (YSZ) was found to yield films of similar electrical properties at different plasma operating conditions. Reflection high energy electron diffraction (RHEED) patterns were used to monitor the a -lattice constant during growth. Films grown on GaN with higher relative atomic flux were found to relax within the first several nm of growth, whereas films grown with higher molecular nitrogen species did not fully relax until approximately 50 nm of growth. These observations suggest that the active nitrogen species plays a significant role in determining how strain is accommodated during InN epitaxy. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)