Effects of indium segregation and well-width fluctuations on optical properties of InGaN/GaN quantum wells

We report the results of calculations for the energies of confined electrons and holes and their wavefunction overlap in InxGa1-xN/GaN quantum wells (QWs) with an indium concentration of x = 15% in the well material. It is known that the observed increase in the photoluminescence lifetime with increasing well width can be explained qualitatively by the reduction in overlap of the electron and hole wave functions, which is caused by the piezoelectric field in the strained QW material. We show that the energy dependence of the lifetime measured across the emission line can be explained in a similar way, as the result of +/-1-monolayer variations in the QW width. We also calculate the energies and electron-hole wave-function overlap for carriers trapped within indium-rich regions of the QW, taking into account the relaxation of the strain field in and around the indium fluctuation. Our results indicate that well-width fluctuations lead to a stronger energy dependence of the lifetime: the magnitude of the effect is the same order as in experiment, and shows a similar increase with increasing well width.