Coherent phonon spectroscopy characterization of electronic bands at buried semiconductor heterointerfaces

Abstract

We demonstrate an all-optical approach to probe electronic band structure at buried interfaces involving polar semiconductors. Femtosecond optical pulses excite coherent phonons in epitaxial GaP films grown on Si(001) substrate. We find that the coherent phonon amplitude critically depends on the film growth conditions, specifically in the presence of antiphase domains, which are independently characterized by transmission electron microscopy. We determine the Fermi levels at the buried interface of GaP/Si from the coherent phonon amplitudes and demonstrate that the internal electric fields are created in the nominally undoped GaP films as well as the Si substrates, possibly due to the carrier trapping at the antiphase boundaries and/or at the interface.