INTRABAND INVERSION DUE TO ULTRASHORT CARRIER LIFETIMES IN PROTON-BOMBARDED INP

We report the evidence of occupation inversion in time average within the continuous band structure of the semiconductor InP. Ultrafast carr ier trapping and recombination (tau approximate to 1x10(-13) s) as a c onsequence of proton bombardment prevents the thermalization of optica lly excited electron-hole pairs (n similar to 3x10(16) cm(-3)). Beyond previous experimental observations of inverted time-averaged luminesc ence spectra, we present experimental data at lower carrier concentrat ions, which are in quantitative agreement with ensemble Monte Carlo si mulations. Inverted electron and hole energy distributions are determi ned quantitatively. We propose the application for a solid-state free- electron laser.