Papers by Author: Galyna Melnychuck

Abstract: 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.

Abstract: Mechanisms and consequences of silicon vapor condensation during SiC epitaxial growth or implant annealing with silane overpressure were investigated. The model for the silicon liquid droplets formation in the gas phase and their deposition on the surface of the SiC substrate was developed. The droplet formation dependence on the silane flow rate, temperature profile in the reactor, and the local temperature variations introduced by the wafer carrier and SiC substrate were investigated.

Abstract: The results of the initial experiments with halogenated carbon precursor chloromethane (CH3Cl) for epitaxial growth of 4H-SiC are presented. The growth rate for mirror-like morphology was easily increased up to about 7 µm/hr at C-rich conditions without detectable surface morphology degradation. Further increase of the silane flow resulted in island formation. The growth with the traditional silane-propane system at the same conditions (and optimized Si/C ratio) produced a very different result, with the growth rate decreasing from upstream to downstream, and morphology degradation taking place for much lower growth rate than in CH3Cl growth. Consequently, the epitaxial growth with chloromethane appears to have significantly different kinetics of the gas-phase precursor decomposition and different mechanisms of the surface reactions, which favors the step-flow growth. In addition, these preliminary data indicated that the maximum achievable growth rate corresponding to the good surface morphology may be noticeably larger for the CH3Cl+SiH4+H2 growth system.