Density Functional Theory (DFT) Simulations and Polarization Analysis of the Electric Field in InN/GaN Multiple Quantum Wells (MQWs)

The ab initio DFT simulations of InN/GaN multiquantum wells (MQW) were used to obtain electric potential profile in the system that, after appropriate averaging procedure, reveal electric field in the wells and barriers and electric potential jumps at the interfaces. The field changes and the potential jumps were used to obtain the density of the polarization charges and the dipole layer at InN/GaN interfaces, respectively. It was shown that polarization dipoles are confined within the one double atomic layers, proving that they have different nature from the dipole layers emerging at the semiconductor surfaces or within p-n junctions. In parallel, a new formulation of polarization analysis, based on the energy minimum principle, was used to determine the electric field in polar InN/GaN multiquantum wells, purely within electrostatic framework, without resorting to experimental data. The obtained fields depend on both the well and the barrier thicknesses. DFT data are in good agreement with the continuum polarization analysis results that were obtained accounting the DFT determined potential jumps and using the standard polarization parameters.