| Popis: |
Strain effects on the polarized optical properties of c-plane and m-plane InxGa1−xN were discussed for different In compositions (x = 0, 0.05, 0.10, 0.15) by analyzing the relative oscillator strength (ROS) and energy level splitting of the three transitions related to the top three valence bands (VBs). The ROS was calculated by applying the effective-mass Hamiltonian based on k · p perturbation theory. For c-plane InxGa1−xN, it was found that the ROS of |X) and |Y)-like states were superposed with each other. Especially, under compressive strain, they dominated in the top VB whose energy level also went up with strain, while the ROS of the |Z)-like state decreased in the second band. For m-plane InxGa1−xN under compressive strain, the top three VBs were dominated by |X), |Z), and |Y)-like states, respectively, which led to nearly linearly-polarized light emissions. For the top VB, ROS difference between |X) and |Z)-like states became larger with compressive strain. It was also found that such tendencies were more evident in layers with higher In compositions. As a result, there would be more TE modes in total emissions from both c-plane and m-plane InGaN with compressive strain and In content, leading to a larger polarization degree. Experimental results of luminescence from InGaN/GaN quantum wells (QWs) showed good coincidence with our calculations. |
