Experimental and Theoretical Tools for the Study of Exciton Properties versus Disorder in Nitride-Based Quantum Structures

We show that resonant Rayleigh scattering measurements combined with conventional reflectivity measurements can easily allow the determination of the most relevant parameters of nitride-based quantum well excitons. In particular, comparing the Fourier-transformed reflection spectra with calculated time-resolved reflectivities, we have found the exciton oscillator strength to decrease dramatically with increase of the QW width in the GaN/Al 0.07 Ga 0.93 N system. The collapse of the oscillator strength is a manifestation of the polarization field effect, as confirmed by our variational calculation. We find that only excitons in very thin quantum wells have an oscillator strength exceeding that of the exciton in bulk GaN.