Nonequilibrium Green's function picture of nonradiative recombination of the Shockley-Read-Hall type

摘要

A quantum-kinetic picture of Shockley-Read-Hall-type (SRH) defect-mediated recombination is derived within the nonequilibrium Green's function formalism for an optoelectronic device with selectively contacted, current-carrying extended states and a localized deep defect state in the energy gap. The theory is first tested for recombination from bulk band states and then implemented for defective bipolar homo- and heterojunction thin-film devices with realistic spatial variation of the band edge profile. While the quantum-kinetic treatment reproduces the semiclassical characteristics for a bulk absorber in flat-band and quasiequilibrium conditions, for which the conventional SRH picture is valid, it reveals nonclassical features such as recombination enhancement by tunneling into field-induced subgap states in the presence of large fields, or the complex recombination current flow at heterointerfaces. Being fully compatible with the rigorous treatment of electron-photon and electron-phonon scattering in the nonequilibrium Green's function (NEGF) formalism, the approach enables a consistent inclusion of defect-mediated nonradiative recombination in comprehensive NEGF simulations of nanostructure-based quantum optoelectronic devices such as quantum well lasers, LEDs and solar cells.