The light emission and in-plane polarization ratio of (0001) GaInN/GaN quantum well structures grown on a stripe-shaped cavity engineered sapphire substrate

Abstract

The asymmetric strain induced effects of (0001) $\mathrm{GaInN}/\mathrm{GaN}$ quantum well structures fabricated on a stripe shaped cavity engineered sapphire (SCES) substrate were theoretically investigated, as a function of indium (In) mole fraction. The results showed remarkable enhancements on the light output intensity and in-plane polarization ratio. When the strain relaxation occurs in the y direction, the peak intensity of linearly polarized light in the x direction increases considerably, while the peak intensity of linearly polarized light in the y direction decreases. This can be attributed to the increment of the optical transition matrix element of x polarized light, which occurs due to the increment of the magnitude of the light hole (LH) wave-function with a negative sign in the y direction, as a consequence of the strain relaxation. The in-plane polarization ratio continues to increase steadily with the increase of strain relaxation, and the rate of increase is more noticeable in QW structures especially in the region of high indium mole fraction.