Structure Design of InGaN-based Blue Laser Diodes with ITO and Nanoporous GaN Cladding Layers

AlGaN is usually used as the cladding layers for GaN-based laser diodes, but it features a low refractive index difference and large lattice mismatch with GaN, resulting in weak optical confinement and large tensile stress, and hence greatly affecting the laser performance. In response, indium tin oxide (ITO) and nanoporous GaN (NP-GaN) with low refractive indices have emerged as promising alternatives. In this study, we conducted simulations to assess the impact of the ITO and NP-GaN thicknesses on device performance through the finite-difference time-domain method. Furthermore, we investigated the influence of nanopore distribution within the NP-GaN, finding that the nanopore size and arrangement near the waveguide layer play key roles. Based on these insights, we propose a novel laser structure with ITO and NP-GaN cladding layers, achieving an 18% increase in the optical confinement factor, along with reductions of 13% in absorption loss and 14% in threshold gain compared to conventional laser diodes utilizing AlGaN cladding layers. It is of great interest to the Ⅲ-nitride semiconductors and semiconductor laser communities.