Analysis of transverse modes of nitride-based laser diodes

We investigated the far-field patterns perpendicular to the junction plane under room-temperature current excitation and analyzed the transverse modes of nitride-based laser diodes with various types of AlGaN cladding layers. It was found that nitride-based laser structures with thin AlGaN cladding layers induce leakage of high-order transverse modes to the outer GaN conta ct layers, even with a relatively high aluminum composition of 15 % in the cladding layers. The perpendicular far-field pattern of the lasers with 0.9 -mu m-thick Al0.07Ga0.93N cladding layers that nearly coincides with that o f the fundamental mode was obtained. From simulation of the maximum optical confinement factor, it was found that the threshold current density decrea ses as the thickness of the AlGaN cladding layer increases in anti-guide-li ke laser structures.