RESONANT RAMAN-SCATTERING PROBE OF ALLOYING EFFECT IN GAAS1-XPX TERNARY ALLOY SEMICONDUCTORS

A comparative study of the alloying effect in GaAs1-xPx (x = 0.90, 0.6 5) ternary alloy semiconductors, using resonant Raman spectroscopy as a probe, is presented. Energy-shifted first-order Raman modes between 600 and 800 cm(-1) and between 1100 and 1200 cm(-1) near resonance is observed. Anomalous enhancement in the oscillator strength for the sec ond-order resonance is observed. These effects can only be understood if the relevant resonant intermediate state is a localized sharp excit on interacting strongly with the LO phonon forming a localized exciton -phonon complex. First-order resonance is found to have contributions from direct band transition and localized excitons, whereas for the se cond-order and third-order resonances, contribution is only from local ized excitons. Increase in localization, binding energy, and lifetime of the excitons is observed with increasing disorder.