Abstract
In this paper we investigate strain and local polarization field effects in zinc-blende indium gallium nitride (InGaN) alloys and quantum wells. To do so we parametrize and establish a Stillinger-Weber potential with parameters fitted to hybrid functional density functional theory data. The developed model gives very good agreement with quantities to which it has not been fitted, such as Kleinman parameters of cubic III-N materials or the composition dependence of the lattice constant in InGaN alloys. Equipped with this model, we extract the composition dependence of elastic constants ${C}_{11}$ and ${C}_{12}$ in InGaN alloys, including bowing parameters for these quantities, which may form input for continuum-based calculations. Furthermore, applying this model to InGaN alloys and wells reveals that random alloy fluctuations can lead to strong local strain field fluctuations. Building on this information, we present a model that allows for the calculation of connected local built-in field fluctuations at the microscopic level, accounting for first- and second-order piezoelectric effects. The approach is general and can be applied to any zinc-blende III--V alloy or heterostructure investigated in the frame of semiempirical models (e.g., valence force field models) targeting strain fields on an atomistic level. Here, building on our Stillinger-Weber potential we show that local strain fluctuations in zinc-blende InGaN quantum wells can lead to strong piezoelectric built-in field fluctuations. This contribution has been widely overlooked in previous theoretical studies of these systems. Finally, we briefly discuss the impact of these polarization field fluctuations on carrier localization effects in such quantum well systems.
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