Free-Carrier Absorption in n-Type Gallium Arsenide

林盛煇(Sunh-Huei Lin) ； 鄭以禎(Yi-Chen Cheng)

《Chinese Journal of Physics》 19卷2&3期 (1981/10) Pp. 76-86

並列摘要

The quantum-mechanical time-dependent second-order perturbation theory is used to calculate the free-carrier absorption coefficient for n-type GaAs at T=300K, and electron concentration ne at 1.09x10^(18) cm^(-3) and 1.3x 10^(17) cm^(-3) respectively. Three major scattering mechanisms (polar optical phonon, acoustic phonon, and ionized impurity scatterings) are included in the calculation and the non-parabolicity of the central valley of the conduction band is also taken into account. The absorption coefficient a is found roughly to obey the power law α~λ^2.86 (ne=1.09x10^18 cm-a) and α~λ^2.72 (ne=1.3x10^17 cm^(-3)) respectively for λ＞3 microns, where λ is the photon wavelength. The corresponding results for the parabolic band are α~λ^2.57 (ne=1.09x10^18 cm-a) and α~λ^2.59 (ne=1.3x10^17 cm^(-3)) respectively. The results of using the non-parabolic band are in much better agreement with experiment. The intervalley scattering between the central vally and the secondary valleys at the (100) directions is also included in the calculation to explain the enhanced absorption for λ＜3 microns. The range of photon wavelength under study is 2 microns ＜λ＜20 microns.