Improved Resolution of Epitaxial Thin Film Doping Using FTIR Reflectance Spectroscopy
Room temperature Fourier Transform Infrared Reflection Spectroscopy (FTIR) was used to investigate the thickness and Free Carrier Concentration (FCC) of heavily and lightly doped 4H and 6H-SiC epitaxial films. Multiple epitaxial layer stacks typical of lateral devices such as the MESFET were grown on 6H-SiC semi-insulating substrates. The estimation of thickness and FCC of the n-channel epi layer is improved by studying the Longitudinal Optical Phonon Plasmon Coupled Modes (LPP). A modelbased analysis of the experimental reflectance spectra from these samples is performed using a dielectric function that accounts for the phonon-photon coupling and plasmonphoton coupling. The value of the LPP+ mode frequency estimated from the reflectance spectrum in the range 600-1200 cm-1 is observed to increase in direct correlation with the electron free-carrier concentration.
Roberta Nipoti, Antonella Poggi and Andrea Scorzoni
M. S. Mazzola et al., "Improved Resolution of Epitaxial Thin Film Doping Using FTIR Reflectance Spectroscopy", Materials Science Forum, Vols. 483-485, pp. 397-400, 2005