Theoretical modelling of exciton binding energy, steady-state and transient optical response of GaN/InGaN/GaN and AlGaN/GaN/AlGaN core-shell nanostructures.

ABSTRACT

Here, we present an efficient 1D model to describe carrier confinement in GaN/InGaN/GaN and AlGaN/GaN/AlGaN core-shell nanostructures (CSNs) within the effective mass framework. A self-consistent procedure combined with hydrogenic model is implemented to estimate exciton binding energy in these CSNs, as a function of CSN dimensions, polarization charge and alloy composition. A 3-fold higher exciton binding energy in these CSNs than that in planar counterparts is attributed to an increased electron-hole overlap. The trend exhibited by the exciton binding energy with polarization charge and alloy composition in the two types of CSNs is significantly different, owing to a drastic difference in the piezoelectric polarizations. A detailed investigation of the steady-state and transient optical response from these CSNs suggests that GaN/InGaN/GaN CSNs emit a wide spectrum. However, that is not the case with AlGaN/GaN/AlGaN CSNs owing to a relatively weaker quantum confined Stark effect. This study is aimed at providing accurate design strategies for UV-blue III-N CSN light-emitting diodes.