Theoretical And Experimental Investigation Of Biexcitons And Charged Excitons In InGaN Single Quantum Dots

Abstract

Micro‐photoluminescence measurements on single InGaN quantum dots at 4K exhibit a rich structure of lines to the high‐energy side of the free exciton (X0), as a function of excitation density. Lines possibly attributable to biexcitons (2X0) and charged excitons (X+ and X−) have been measured. We model the dots as truncated cone shapes, using a self‐consistent finite difference method in the Hartree approximation to compute the ground‐state wavefunctions of the four exciton complexes. We calculate the exciton recombination energy (X0) and the magnitude of the blue‐shifts of the biexciton and charged excitons as a function of dot size and composition. The transition energy depends strongly on both dot composition and dot height, while the magnitude of the blue shift is determined primarily by the piezoelectric field‐induced separation of electrons and holes. We use these two separate effects to place constraints on allowed models for the QDs. The experimentally measured energies are in agreement with these theoretical calculations.