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, 0.65) 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 second-order resonance is observed. These effects can only be understood if the relevant resonant intermediate state is a localized sharp exciton 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 second-order and third-order resonances, contribution is only from localized excitons. Increase in localization, binding energy, and lifetime of the excitons is observed with increasing disorder.