Internal electric field effects at ordered Ga/sub 0.5/In/sub 0.5/P/GaAs heterointerface investigated by photoreflectance spectroscopy

We performed photoreflectance (PR) and Raman-scattering measurements of long-range ordered Ga/sub 0.5/In/sub 0.5/P/GaAs heterointerfaces to investigate effects of the internal electric field on the carrier-modulation mechanism. The PR spectrum of an ordered Ga/sub 0.5/In/sub 0.5/P/GaAs heterointerface shows the Franz-Keldysh oscillation due to a strong internal electric field. However, the PR-signal amplitude for the ordered sample is /spl sim/1/20 of that for a disordered sample. Raman-scattering results of the ordered Ga/sub 0.5/In/sub 0.5/P/GaAs heterointerfaces reveal plasmon-phonon coupled modes due to the spontaneous electron accumulation. We suggest that the electron accumulation reduces the mean electric field for the PR modulation.