Strong evidence for diffusion of point defects in GaInN/GaN quantum well structures

The reduction of the defect density in quantum wells (QWs) is important to maximize the internal quantum efficiency. We investigate non-radiative recombination in GaInN/GaN single QWs (SQWs) grown on In-free and In-containing so-called underlayers (ULs). The non-radiative lifetime of SQWs increases with increasing UL thickness and decreases exponentially with increasing UL growth temperature. Moreover, the presence of low-temperature UL strongly increases the non-radiative lifetime of SQWs. As non-radiative recombination at threading dislocations is efficiently suppressed by means of V-pits, our results suggest that point defects diffuse from the high temperature buffer layer through the UL into the QW. The resulting point defect density in the QW is strongly influenced by the UL growth conditions.