Investigation Of Optical Polarization Characteristics For An Algan-Based Quantum Well Structure

The anisotropic optical properties of an AlGaN-based quantum well (QW) structure are investigated by using the effective-mass theory. Firstly, the crystal-field bowing parameter (b(cr) = -0.087) and the slope (b(s) = 8) of the crystal-field splitting energy ( increment (cr)) - in-plane strain (e(xx)) curve are obtained by comparing the calculated degree of polarization (DOP) of the AlGaN alloy with the experimental values. Then, the DOP of Al0.35Ga0.65N/AlxGa1-xN single QW structures with various Al-content (x = 0.5, 0.45, 0.55) in the barrier layer is calculated by employing the obtained parameters. The DOP is enhanced from -43.15% to -4.47% with increasing Al-content atJ = 100 A cm(-2). By increasing the injection current density or the residual strain in the active region, the DOP can be increased/decreased by modulating the Al component of the barrier layer due to the different polarization characteristics of the transition levels. In addition, the AlGaN-based QW structure with lower Al-content in the barrier layer shows the larger spontaneous emission rate.