On the coherence/incoherence of electron transport in semiconductor heterostructure optoelectronic devices

Abstract

This paper compares and contrasts different theoretical approaches based on incoherent electron scattering transport with experimental measurements of optoelectronic devices formed from semiconductor heterostructures. The Monte Carlo method which makes no a priori assumptions about the carrier distribution in momentum or phase space is compared with less computationally demanding energy-balance rate equation models which assume thermalised carrier distributions. It is shown that the two approaches produce qualitatively similar results for hole transport in p-type Si 1−x Ge x /Si superlattices designed for terahertz emission. The good agreement of the predictions of rate equation calculations with experimental measurements of mid-and far-infrared quantum cascade lasers, quantum well infrared photodetectors and quantum dot infrared photodetectors substantiate the assumption of incoherent scattering dominating the transport in these quantum well based devices. However, the paper goes on to consider the possibility of coherent transport through the density matrix method and suggests an experiment that could allow coherent and incoherent transport to be distinguished from each other.

Intervalley Scattering and the Role of Indirect Band Gap AlAs Barriers: Application to GaAs/AlGaAs Quantum Cascade Lasers

“…Here we again consider a single quantum well, with the well width d 1 taken as 35Å and the barrier d 2 as 20Å. The total sheet density N d is taken as 10 10 cm −2 and we also investigate the dependence on the lattice temperature and the case of the electron temperature different from the lattice temperature [34], T e = T latt . Again, the results for the lower temperatures are difficult to discern, which necessitates the use of a log scale.…”

“…Also shown are the X potential profile and the corresponding X-states. We determine the self-consistent scattering rates, accounting for all electron-longitudinal-optical phonon and electronelectron scattering rates as well as an evaluation of the non-equilibrium electron distribution [34,35]. Fig.…”

Coherent transport in QCLs: a new theoretical approach

“…While earlier publications [1][2] argued that current transport in QCLs is mainly incoherent, more recent publications [3][4][5] emphasize the important role played by coherence.…”