Strain effect on polarized optical properties of c -plane GaN and m -plane GaN

Abstract

The polarized optical property of c-plane and m-plane GaN with varying strain was discussed by analyzing the changes of relative oscillator strength (ROS) of the three transitions related to the top three valence bands. The ROS was calculated by applying the effective-mass Hamiltonian based on k · p perturbation theory. For c-plane GaN, it was found that ROS of X> -like state and Y>-like state were superposed with each other. Especially, they increased with compressive strain, while that of |Z> decreased in the second band. For m-plane GaN under compressive strain, the first three bands were dominated by |X>, |Z> and |Y>-like states, respectively, which led to nearly linearly-polarized light emissions. With compressive strain, the ROS of |X>-like state increased more rapidly than |Z>-like state in the topmost valence band. As a result, TE mode emissions from both c-plane and m-plane GaN increased more rapidly than TM mode emission with compressive strain, leading to larger polarization degree. Experimental results of luminescences from InGaN/GaN quantum wells showed good coincidence with our theoretical calculations.