1st Leibniz MMS Days - Abstract
Marquardt, Oliver
Continuum models of semiconductor heterostructures on the nanoscale represent a computationally inexpensive and robust approach to the elastic, piezoelectric, and optoelectronic properties of nanostructures such as thin films, quantum dots, or nanowires (NWs). Despite the incapability of these models to account for the atomistic nature of the underlying crystal lattice, continuum-based approaches such as linear elasticity theory or multiband k*p models can still be considered the workhorse for the simulation of semiconductor devices on the nanoscale. We present an approach for the continuum-based simulation of elastic, piezoelectric, and electronic properties of semiconductor nanostructures, which is generalized such that it facilitates the application of different elastic tensors, polarization vectors, and k*p Hamiltonians. Our model is based on a plane-wave framework and has been implemented within the S/PHI/nX software library. As an example, we consider axial (In,Ga)N/GaN NW heterostructures. Due to the very different band gaps of InN and GaN, their ternary alloy in principle enables light emission and absorption throughout the entire visible spectrum. However, it is difficult to produce (In,Ga)N layers on GaN with high In content and high structural quality, due to the large lattice mismatch of InN and GaN. By embedding thin (In,Ga)N disks in GaN NWs instead, this problem can be overcome because the highly strained (In,Ga)N layer can relieve its strain elastically. Correspondingly, much research effort has been dedicated to the investigation of these structures in order to exploit their potential for novel light emitters or energy harvesting applications. We discuss different aspects of the modelling process, such as the treatment of interfaces or individual atomistic impurities, and evaluate the capability of our simulations to explain experimental observations. Finally, we review the limitations of the models employed and their impact on the simulations, and evaluate possible strategies for improvement.