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.
The influence of the width of a lattice-matched Al 0.82 In 0.18 N/GaN single quantum well (SQW) on the absorption coefficients and wavelength of the intersubband transition (ISBT) has been investigated by solving the Schrdinger and Poisson equations self-consistently.The wavelength of 1-2 ISBT increases with L,the thickness of the single quantum well,ranging from 2.88 μm to 3.59 μm.The absorption coefficients of 1-2 ISBT increase with L at first and then decrease with L,with a maximum when L is equal to 2.6 nm.The wavelength of 1-3 ISBT decreases with L at first and then increases with L,with a minimum when L is equal to 4 nm,ranging from approximately 2.03 μm to near 2.11 μm.The absorption coefficients of 1-3 ISBT decrease with L.The results indicate that mid-infrared can be realized by the Al 0.82 In 0.18 N/GaN SQW.In addition,the wavelength and absorption coefficients of ISBT can be adjusted by changing the width of the SQW.
