Nonequilibrium many body theory for quantum transport in terahertz quantum cascade lasers

Abstract

This paper presents a predictive Keldysh nonequilibrium many body Green's functions theory for quantum transport including high order electron-electron, electron-phonon, electron-impurity, and interface roughness scattering processes. Our approach is fully frequency and momentum dependent including nondiagonal dephasing terms in both frequency and k-space. A detailed balance between coherent and scattering processes leads to local current conservation even if a small number of states is considered. Good agreement with experiments is obtained for a terahertz quantum cascade laser. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3272675

Automated numerical characterization of dilute semiconductors per comparison with luminescence

“…Therefore, in this project, we did not fully calculate the dephasing attributed to electron-phonon, electron-impurity and electron-alloy disorder scattering and that leads to measured s-shape-like features in dilute semiconductor samples (Imhof et al 2010;Kesaria et al 2015). The scattering processes cited above can all be described by selfenergies (Pereira 1995;Wacker 2002;Schmielau and Pereira 2009). Instead, we used Trust RegionReflective (TRR) methods (Hung 2012) to obtain the values of carrier density, homogeneous and inhomogenous broadening that best characterize experimental results and as a future step, we shall use these numbers to compare and contrast with Nonequilibrium Green's Functions (NEGF) calculations to help determine the relative influence of each scattering/dephasing mechanisms.…”

Intersubband gain without global inversion through dilute nitride band engineering

“…We still found considerable gain for the same global densities and electronic temperatures 100 K higher in the upper subbands. Future work will use an extended version of our fully nonequilibrium approach 16,23 that will start from the solutions of the Hamiltonian used here for each layer. In summary, this theoretical proof of concept shows that it is possible to engineer conduction subbands with substantial differences in effective masses which make gain without global inversion feasible in dilute nitride heterostructures.…”

“…The dephasing used in the numerical inversion is a frequency and momentum dependence approximation to the single-plasmon-pole dynamically screened dephasing of Ref. 16 further simplified by a quasiparticle approximation with thermal distributions. The proof of concept structure chosen is a 7 nm Ga 0.98 N 0.02 As/ Al 0.3 Ga 0.…”

“…They further do not include relevant scattering mechanisms and many particle corrections that increase their relevance as the electronic density increases to reach the gain regime. 16 In this paper we investigate the possibility of ISB gain without global inversion by engineering the conduction band effective masses using the NGF approach. The upper gain subband has an effective mass made considerably smaller than the lower lasing subband that could not be obtained in conventional III-V materials where the electron effective mass is proportional to energy gap.…”

Simulations of mid infrared emission of InAsN semiconductors

“…We thus replace it with the Hulthén potential [18]. We use an analytical average for the dephasing Γ that partially simulates the electron-electron, electron-phonon and electron-impurity scattering [20][21][22], which would be required for increased predictability and are being included in the approach for dilute nitrides.…”