Transient four-wave-mixing spectroscopy on gallium nitride: Energy splittings of intrinsic excitonic resonances

Abstract

We present transient and spectrally resolved four-wave-mixing studies on excitonic transitions in GaN with wurtzite structure. Coherent excitation of the $A$ and $B$ excitons results in a pronounced beating with a period of 0.520 ps, corresponding to an $A\ensuremath{-}B$ splitting of (7.98\ifmmode\pm\else\textpm\fi{}0.03) meV. A biexcitonic binding energy of (5.7\ifmmode\pm\else\textpm\fi{}0.3) meV is obtained from the power spectrum of the four-wave-mixing signal.