Abstract-Density dependence of the terahertz absorption spectra in optically excited semiconductors

1. Yen Thi Hai Le and Takeshi J. Inagaki^*

Article first published online: 25 NOV 2014

DOI: 10.1002/pssb.201451191

http://onlinelibrary.wiley.com/doi/10.1002/pssb.201451191/abstract

We theoretically investigate the terahertz (THz) absorption spectra in optically excited direct bandgap bulk semiconductors for various electron–hole (e–h) pair densities with analyzing Coulomb interacting two-band e–h systems. The exciton Mott transition (the density ionization) can clearly be studied because, above the critical density, the exciton structures originating from the intraexciton transitions disappear and only the Drude component is obtained. The present theory also predicts that the transition energy from 1s to 2p states is almost independent of density below the exciton Mott density. We also study the interplay between the density ionization of excitons and the abrupt increase in the ionization ratio and in the e–h quasi-chemical potential owing to the quantum dissociation.