HOMOGENEOUS AND INHOMOGENEOUS LINEWIDTHS OF EXCITONS IN PARTIALLY ORDERED GA0.52IN0.48P

We report picosecond four-wave mixing experiments on Ga0.52In0.48P gro wn by organometallic vapor phase epitaxy on GaAs substrates. The spect ral behavior of the homogeneous linewidth in the range of the inhomoge neously broadened band gap excitonic resonance is found to be differen t for a more disordered as compared to a partially ordered structure. Whereas the former shows the normal alloy behavior, the behavior of th e partially ordered sample supports the assumption that its structure consists of ordered domains with varying degrees of order. This means, in particular, that the main origin of the inhomogeneous broadening i s different for the disordered and ordered case. In addition, a polari zation dependence of the four-wave mixing signal is only observed for the more disordered sample. (C) 1994 American Institute of Physics.