Effects of GaN capping layer on carrier occupation and interband transition probability of vertically coupled InGaN/GaN quantum dots

The carrier occupation and the interband transition probability of wurtzite (WZ) coupled InGaN/GaN quantum dots (QDs) were investigated as a function of the distance d between QDs in a range of 30–70 Å. The light emission intensity rapidly decreases with increasing the distance d and becomes minimum near d=50 Å. This can be explained by the fact that the matrix element values are significantly reduced with increasing d owing to an increase in the internal field and the quasi-Fermi-level separation shows a minimum value at d=50 Å. However, the light intensity slightly begins to increase when d exceeds 50 Å because the quasi-Fermi-level separation increases with increasing d. These results can be used as the design guideline of the active region in QD-based optoelectronic devices with a high efficiency. •The matrix element values are significantly reduced with increasing d between QDs.•The quasi-Fermi-level separation shows a minimum value at d = 50 Å.•The quasi-Fermi-level separation increases with increasing d for d ¿ 40 Å.•The light emission intensity rapidly decreases with increasing the distance d.•The light emission intensity becomes minimum at d = 50 Å.