Optoelectronic response calculations in the framework of k·p coupled to non-equilibrium Green's functions for one-dimensional systems in the ballistic limit

Abstract

We present theory of the carrier-optical interaction in 1D systems based on the nonequilibrium Green's function formalism in the 4 × 4 k·p model. As representative parameters, we chose the GaAs. Results and discussion section is based on the simplified model such as 2 × 2 k·p model (two transverse modes). Even though 2 × 2 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 kept intact. This allows us to study not only quantitative effects but also qualitative behaviour.