On the incoherence of quantum transport in semiconductor heterostructure optoelectronic devices

This paper compares and contrasts different theoretical approaches with experimental measurements of transport in optoelectronic devices based on 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 the specific case of hole transport in p-type Si_1-xGe_x/Si superlattices designed for terahertz emission though there are significant differences which originate in the absolute values of the carrier kinetic energy in the plane of the quantum wells. In contrast to this, simulations of electron transport in n-type GaAs/Ga_1-xAl_xAs terahertz quantum cascade lasers show a more similar behaviour between both theoretical approaches. In addition, the very good comparison with experiment substantiates the incoherent scattering approach which underpins both methods. Further evidence to support the applicability of carrier transport in semiconductor heterostructures at finite temperature being dominated by incoherent scattering, which can be modelled by self-consistent energy-balance rate equations, is given by further comparisons with experimental measurements of two other categories of devices namely quantum well infrared photodetectors and quantum dot infrared photodetectors