Off-center electron transport in resonant tunneling diodes due to incoherent scattering

Abstract

Coherent transport through resonant tunneling diodes at high bias is determined by the transfer of carriers described by momentum and energy from a bath in the emitter through a central resonance to the collector. Simplified treatments of coherent carrier transport assume the transverse carrier dispersions to be identical and parabolic in the emitter and central device. This results in a carrier transport that is dominated by carriers at the ⌫ zone center. Other work has shown that more realistic dispersions result in off-zone center current flow. Incoherent scattering adds more degrees of freedom to match the emitter energy and momentum (E em ,k em ) with the resonance energy and momentum (E res ,k res ) with (⌬E scatt ,⌬k scatt ). It is shown analytically and numerically that this additional degree of freedom redirects carriers in energy and momentum space resulting in an off-zone center current for large voltage regions. Interface roughness, polar optical phonon, and acoustic phonon scatterings are explicitly considered.

Spin tunneling through an indirect barrier: Tight-binding calculations

“…The practical aspect of focusing the electrons to energies within the large-polarization window can be achieved by placing an RTD structure in front of the tunneling barrier. In this way, one not only can control the incoming energy of the electrons but also ensures that most electrons have non-vanishing transverse momenta 31 and, consequently, their energies are spin-split.…”

Ab-initiocalculations of spin tunneling through an indirect barrier

“…For instance, electronic states with the same energy, corresponding to k || and -k || , will have opposite spins, thus the total current will carry the same amount of spin-up and spin-down. To fix these aspects we already suggested [3] that the electrons should be injected from a resonant tunneling diode in order to focus the electrons in the k || -plane [26]. Moreover, by applying a voltage bias in the k || -plane of the emitter [27,28], the isotropy of k || will be further broken, thus a net spin polarization will be induced in the energy window.…”