Optical properties of AlN/sapphire grown at high and low temperatures studied by variable angle spectroscopic ellipsometry and micro Raman scattering

摘要

Abstract: Variable angle spectroscopic ellipsometry (VASE) andmicro Raman scattering have been employed to study theoptical anisotropy and optical constants of AlN filmsgrown at high and low temperature (HT and LT). The AlNfilms were grown by metalorganic vapor phase epitaxy(MOVPE) and molecular beam epitaxy (MBE) on c-planesapphire ($alpha@-Al$-2$/O$-3$/) substrates,respectively. Anisotropic optical phonon spectra of AlNhave been measured along two directions so that theoptical axis $LS@c$GRT of AlN is either perpendicularor parallel to the polarization of the incident beam.Nonzero off-diagonal elements A$-ps$/ and A$-sp$/ ofJones matrix in the reflection VASE (RVASE)measurements indicate that the $LS@c$GRT of AlN isslightly away from surface normal due to substratemiscut. The ordinary optical constants of both HT AlNhave been determined spectroscopic ellipsometry atsmall angles of incidence so that the extraordinaryresponse is greatly reduced. The film thickness alongwith the surface overlayer was determined via the VASEdata analysis as well. !17