SPECTROSCOPIC ELLIPSOMETRY AND LOW-TEMPERATURE REFLECTANCE - COMPLEMENTARY ANALYSIS OF GAN THIN-FILMS

We report spectroscopic ellipsometry (SE) and low-temperature reflecta nce data on epitaxial GaN thin-film samples covering the widest range of tensile and compressive stress (-3.8 to 3.5 kbar) thus far. SE allo ws us to assess the preparation of smooth and abrupt GaN surfaces by c hemical treatments in real time, and, coupled with the reflectance dat a. the Edn/dE contribution to dispersion, which is important for laser action. The reflectance data explicitly show the non-linear behavior of the B-A and C-A splittings vs. the energy of the A exciton. Linesha pe ambiguities that hindered previous interpretations have been resolv ed with reciprocal space analysis, allowing us to obtain band paramete rs such as Delta(SO) = 17.0 +/- 1 meV and Delta(CF) = 9.8 +/- 1 meV wi th increased confidence. (C) 1998 Published by Elsevier Science S.A.