Thursday, July 4, 2013

1307.0580 (Andrei K. Buin et al.)

Optoelectronic response calculations in the framework of k.p coupled to
Non-equilibrium Green's functions for 1D systems in the ballistic limit

Andrei K. Buin, Amit Verma, Simarjeet Saini
We present theory of the carrier-optical interaction in 1D systems based on the non-equilibrium Greens function formalism in the 4x4 k.p model. As a representative parameters we chose the GaAs. Although theory is presented in 4x4 k.p many subbands, results and discussion section is based on the simplified model such as 2x2 k.p model (two transverse modes). Even though 2x2 k.p model is simple enough it shows many phenomena that have not been seen before. We focus mainly on the ballistic extraction of photogenerated free carriers at the radiative limit which is described by the self-energy term derived in dipole approximation and solved in self-consistent manner with Keldysh quantum kinetic equations. Any relaxation or non-radiative recombination mechanisms as well as excitonic features are neglected. Effect of non-locality of electron-photon self energy term is considered and discussed. Spontaneous emission is also considered and shown to be small in short devices under medium bias conditions. Electron and hole spatial current oscillations are seen and discussed. It is shown that neglecting off-diagonal correlation in the band index not only produces quantitatively wrong results but it also alters the qualitative picture. All simulations are done in the full-rank approximation, with all spatial and band correlation effects are kept intact. This allows us to study not only quantitative effects but also qualitative behaviour.
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