Effect of piezoelectric constants in electronic structures of InGaN quantum dots

Abstract

This study theoretically investigates the effect of the sign of the shear piezoelectric constant on the optical properties of wurtzite InGaN quantum dots (QDs) that are grown on polar, semipolar and nonpolar GaN substrates. The strain fields, electric potentials and single- particle state energies are analyzed using the theory of piezoelectricity and the strained k · p Hamiltonian. Calculations reveal that the sign of e15 greatly affects the electric potentials and optical properties, especially of larger QDs. The change in electron energy is particularly sensitive to the height of QDs for either sign of e15. A positive e15 causes a greater decrease (increase) in electron (hole) energies than a negative e15. Furthermore, the exciton binding energy of polar QDs is sensitive to dot height, unlike semipolar and nonpolar QDs, which have weak binding energies. The transition energies of InGaN QDs in semipolar or nonpolar substrates are greatly increased. However, the overlap of the electron–hole wavefunctions is clearly greater when the indium content is lower. Based on the results herein, QDs grown on (1 1 0 1) planes should be preferred to those grown on polar and nonpolar planes for optical applications.