Electronic structure of ordered Ga0.5In0.5P/GaAs heterointerface studied by Raman-scattering and photoluminescence-excitation measurements

We have investigated the electronic band structure of a long-range-ordered Ga0.5In0.5P/GaAs heterointerface by optical measurements and a semi-empirical calculation. Raman-scattering spectra of the ordered Ga0.5In0.5P/GaAs samples show plasmon-phonon coupled modes induced by dense electron accumulation at the heterointerface, in contrast to that of the unordered sample which shows the spectrum of bulk GaAs. Furthermore, the Franz-Keldysh oscillation observed in the photoluminescence-excitation spectrum indicates a strong interface electric field. According to the results of a comparison between the experiment and a semi-empirical calculation based on Poisson's law, it is found that the spatial distribution of the accumulated electron density is modified strongly by the conduction-band discontinuity and the interface field, depending on the order parameter.