IN-SITU RAMAN MONITORING OF THE MOLECULAR-BEAM EPITAXIAL-GROWTH OF GALLIUM NITRIDE

Raman spectroscopy was applied to monitor the growth of GaN st tempera tures around 600 degrees C without interrupting the growth process. Ga N was deposited on GaAs(100) and Si(111) substrates by molecular beam epitaxy using elemental Ga and atomic nitrogen provided by an r.f. pla sma source. Sufficient signal-to-noise ratio in the spectra was achiev ed by carefully choosing the excitation photon energy in the vicinity of the bandgap at the elevated temperature and thus realizing conditio ns for resonant Raman scattering. Owing to the difference in bandgap e nergy of 0.2 eV between the distinct modifications of GaN, the resonan ce condition also leads to a selective enhancement of the scattering c ross-section of either the cubic or the hexagonal phase. (C) 1997 John Wiley & Sons, Ltd.