Photoemission of metal-semiconductor structures: Novel spectroscopy for high field transport

We present a new technique for spectroscopic analysis of high-field electronic transport, as a function of both energy and distance. We measure the energy of electrons photoemitted into ultra-high vacuum from a biased InP/Ag metal-semiconductor structure after crossing the high electric field band bending region (BBR). The work function of this structure is lowered by cesium and oxygen coadsorption so that photoemission is obtained under light excitation at an energy equal to the bandgap. The study of the energy distribution curves of the emitted electrons versus reverse bias allows to obtain the energy distribution inside the solid as a function of distance travelled in the BBR. We evidence ballistic transport over a distance of 4500 Å, over a kinetic energy range which approximately spans the entire first conduction band. A high-energy structure is resolved for a bias larger than 0.3 V. The study of the energy position of this structure as a function of bias allows direct visualization of intervalley transfer and to directly measure an estimate value of the mean free path associate with this phonon scattering process.