INHOMOGENEOUS EXCITON BROADENING AND MEAN FREE-PATH IN IN1-XGAXASYP1-Y-INP HETEROSTRUCTURES

Absorption and electroabsorption spectra are investigated at low tempe rature to derive broadening parameters of excitonic absorption edges i n the alloy crystals, A strong increase of the inhomogeneous linewidth of excitons is observed for quaternary material which exceeds signifi cantly the width expected from compositional fluctuations, The linewid th decreases again for phosphorous rich samples, Franz-Keldysh oscilla tions above the absorption edge contain information on the coherence l ength of band states, They show a corresponding decrease of the mean f ree path from 150 nm for ternary material to 70 nm for quaternary mate rial.