Improvement of TE-polarized emission in type-Ⅱ InAlN-AlGaN/AlGaN quantum well

The optical properties of the type-Ⅱ lineup In_xAl_1-xN-Al_0.59Ga_0.41N/Al_0.74Ga_0.26N quantum well (QW) structures with different In contents are investigated by using the six-by-six K-P method. The type-Ⅱ lineup structures exhibit the larger product of Fermi-Dirac distribution functions of electron f_cⁿ and hole (1-f_v^Um) and the approximately equal transverse electric (TE) polarization optical matrix elements (|M_x|²) for the c1-v1 transition. As a result, the peak intensity in the TE polarization spontaneous emission spectrum is improved by 47.45%-53.84% as compared to that of the conventional AlGaN QW structure. In addition, the type-Ⅱ QW structure with x~0.17 has the largest TE mode peak intensity in the investigated In-content range of 0.13-0.23. It can be attributed to the combined effect of|M_x|² and f_cⁿ (1-f_vUm) for the c1-v1, c1-v2, and c1-v3 transitions.