Laser-Modulated Photoemission in Semiconductors

Abstract
A novel, double-beam photoemission experiment is described in which electron energy distributions are obtained from semiconductors by modulating the ultraviolet photocurrent with a tunable, flash-excited, dye-laser beam. Double-beam photoemission spectra are demonstrated, in the case of tellurium, to result from optical transitions alone within the unperturbed bulk band structure of the solid. Unique information is obtained on the conduction-band-states distribution below vacuum level, within which a forbidden gap is demonstrated to exist between 2.5 and 4.7 eV above valence-band edge.