Fully coupled and semi-coupled piezoelectric models on the optical properties of InGaN quantum dots

This paper investigates the differences between the fully coupled and the semi-coupled piezoelectric models for determining strain fields, piezoelectric potentials and optical properties of wurtzite InGaN quantum dots (QDs) in three different shapes. Through the calculations, we show that the relative difference of the x-component strain inside the dot remains almost unchanged regardless of the shapes and the sizes of the dot. On the other hand, a large relative difference for the z-component strain is obtained with the use of the semi-coupled model. We also find that the semi-coupled model clearly overestimates the piezoelectric potential, and the transition energy difference increased with increases in the dot size and indium composition. Consequently, the semi-coupled model causes a great amount of distortion in predicting the optical properties of InGaN QDs. It is thus evident that the fully coupled model for calculating the electromechanical fields and optical properties of InGaN QDs may be more appropriate according to our numerical examples.