Analysis of the role of defects in the Performance characteristics of GaN-based exciton-polariton lasers

Abstract

This study emphasizes on the theoretical analysis of defect on bosonic system, especially exciton-polariton bosonic system. Presence of defect may either stand as a barrier to realization of such phenomenon or pave the way for realization of something more exotic. This work is focused on the influence of defect on polariton lasing here. In polariton lasers using semiconductor microcavity with high quality factor, stimulated scattering facilitates dynamic condensation process. As a result, a macroscopic and coherent exciton-polariton state is formed. In this metastable coherent phase, condensate is not thermalized with the lattice rather thermalized among itself, according to micro-cannonical thermalization. Thus, effective polariton temperature of condensate near K=0, is generally larger than lattice temperature. Recently, for a defective MC, measured effective polariton temperature is sustainably smaller than 300K, for room temperature operation of GaN polariton diode lasers. Such finding is completely different from the generic case. With higher density of dislocation and other related defect in the active region of microcavity, this temperature lowering effect reinforce itself. To investigate the effect of defect on condensate formation and to explain phenomenon like this, open dissipative Gross-Pitaevskii (GP) equation coupled with external exciton reservoir has been solved numerically. Several situations have been considered regarding defect potential and pumping scheme. Open dissipative GP equation enables us to investigate the vortices kinetics during condensate formation with the presence of disorder potential and for different pumping scheme. To estimate the exciton polariton LASER performance with the presence of defect, semi-classical Boltzmann equations have been solve numerically. Along with all these, a thermodynamic approach with numerical solution of Bose-Hubbard model has been analyzed to understand the behavior of the system from different point of view. High frequency performance of such polariton laser diode is analyzed using simplified rate equation model. Finally, comparison between numerical and experimental result for polariton LASER diode has been provided.