We have calculated the free-carrier absorption coefficient for polar III–V semiconductors with strong LO phonon–plasmon interaction. We took several mechanisms into account, which assist in the photon absorption process. At the considered doping concentrations the most important scattering mechanisms are thermal LO phonon branch scattering, impurity scattering, plasmon branch scattering and acoustic phonon scattering. For all these interaction potentials screening by conduction electrons has been included. Computations are performed for β-GaN and α-GaN doped semiconductors at different mid-IR wavelengths and doping concentrations. For all considered cases the relative difference between the Drude model calculation results based on static and dynamic damping factors is typically smaller than 25–30%.
To cite this version:S Rabbaa, J Stiens. Charge density and plasmon modes in a triangular quantum well model for doped and undoped gated AlGaN/GaN HEMTs. Journal of Physics D: Applied Physics, IOP Publishing, 2011, 44 (32) Abstract. We have calculated the plasmon frequency of the two-dimensional electron gas (2DEG) in AlGaN/GaN high electron mobility transistors (HEMT). The impact of HEMT's parameters on the plasmon frequency and the sheet charge density of the 2DEG is discussed in detail. The charge density in the HEMT's channel is calculated by means of a triangular quantum well (TQW) model. It has been found that the AlGaN/GaN heterostructure induces plasmon oscillations in the THz range with larger frequencies compared to other semiconductor compounds. The sensitivity of the tunability of these frequencies is considerable, especially by using a variable applied gate voltage. We have derived optimal structure parameters for obtaining a maximum plasmon frequency for a given doping concentration. We will show that the accuracy of this optimized frequency value is dependent on the average position ∆d of charge density in the triangular shaped (quantum well) channel. The interaction between radiation and plasmons has many applications such as detectors, mixers and generators of THz waves.
The model to calculate the free‐carrier absorption coefficient for polar III–V semiconductors with strong LO phonon–plasmon interaction was generalized by taking into account free‐carrier scattering by defects The following main mechanisms assisting in the photon absorption process, where taken into account: thermal phonon‐like branch and plasmon‐like branch scattering, impurity scattering, and acoustic phonon scattering. To calculate the contributions of phonon–plasmon coupled modes into the absorption coefficient, the integral dispersion equation for coupled mode frequencies was obtained taking into account free electron scattering by imperfections (mainly by charged impurities in highly doped semiconductors); the dispersion relation of phonon–plasmon coupled modes were calculated versus electron concentration. Computations are performed for α‐GaN and GaN doped semiconductors at different mid‐IR wavelengths and electron concentrations. For all considered cases, the relative difference between the Drude model calculation results based on static and dynamic damping factors is typically smaller than (25–35)%.
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