Experimental investigation of the infrared absorption saturation in p-type germanium and silicon

Abstract

We investigate the room-temperature absorption saturation of p-Ge and p-Si for several samples over a range of doping densities for light having wavelengths of 10.6 and 9.6 μm. The transmission data can be fairly well described using an intensity dependent absorption coefficient characteristic of an inhomogeneously broadened two-level system. Measurements of the saturation intensity of p-Ge show that Is increases monotonically with increasing hole concentration, and that the resonant transition is significantly easier to saturate in p-Ge than in p-Si for the samples we examined.

Optical Properties of Small Band Gap Semiconductors Subject to Laser Excitation. Nonlinear Infrared Properties of Semiconductors.

“…The measured values of Is for p-Si at 10.6rmn and 9.6mm are shown In Table V. 30 We see that I s is considerably larger for Si than Ge, which is primarily due to the larger hole-phonon scattering rates and the smaller excitation rates In Si. In addition, lattice absorption is much larger in Si than Ge for the wavelengths of interest.…”