Picosecond Infrared Spectroscopy in Narrow-Gap Semiconductors

Abstract

Presently, narrow-bandgap semiconductors occupy an increasingly important role in mid-infrared electro-optics. They are also interesting from a purely physical point of view because of characteristics arising from their bandstructure. One example of experimental interest to us concerns the properties of dense, nonequilibrium electron-hole gases in such materials as PbTe, Hg_1-xCd_xTe and InSb. In particular, we have applied picosecond infrared techniques at 10.6 ym and 5.3 pm to the study of the highly degenerate plasmas in these semiconductors. The emphasis in the work discussed below centers on the transient dynamics of the electron-hole system, specifically the recombination kinetics. Our measurements have provided a first indication of recombination rates at excess densities n≳10¹⁹cm⁻³.