Optical Gunn effect in n-doped GaAs at mid- and far-IR wavelengths

摘要

Abstract: In this paper a rigorous quantum mechanical multi-valley model is developed to assess the optical equivalent of the electrical Gunn effect: a laser beam pumps free electrons from the central conduction band valley of n-doped bulk GaAs towards its satellite values. The computational complexities involve a central fully nonparabolic degenerated $Gamma@- valley, an anisotropic L-valley of arbitrary degeneracy, impurity assisted, thermal and hot polar optical phonon assisted intravalley absorption mechanisms, and intervalley phonon assisted equivalent and nonequivalent intervalley absorption mechanisms. The influences of the doping concentrations, electron temperature, optical power density and the equivalent LL-intervalley deformation potential (IDP) on the magnitude and relaxation time of the optical Gunn effect are discussed and compared with experimental results. We found that the optically induced nonlinear absorption and intervalley transfer strongly depend on the equivalent LL-IDP. The large scattering on the available data for LL-IDP leads to large variations in the theoretical estimations. Under optical plasma resonance conditions we find an energy relaxation time in the L-valley of about 0.3 to 2.2 ps, a nonlinear refractive index n$-2$/ of about 2.7 to 3.75 $MUL 10$+$MIN@81$/ cm$+2$//W and e.g. a 10 percent electron transfer of about 1.8 to 3.2 MWcm$+$MIN@2$/. !24