Band offsets measured by internal photoemission-induced second-harmonic generation

We report first band-offset measurements obtained by multiphoton internal-photoemission induced second-harmonic generation. Our two-color contactless laser technique involves (1) optically pumping electrons into the oxide and (2) probing the resulting interface electric field using time-dependent second-harmonic generation. One- and two-photon internal-photoemission thresholds for the Si/SiO₂ interface were measured to be 4.5 and 2.25 eV, respectively. This method promises to become a valuable experimental tool in determining band offsets in wide variety of semiconductor interfaces.