Design of GaN-Based Laser Diode Structures with Nonuniform Doping Distribution in a p-AlGaN Cladding Layer for High-Efficiency Operation

In GaN-based laser diode (LD) structures, it is essential to optimize the doping concentration and profiles in p-type-doped layers because of the trade-off between laser power and operation voltage as the doping concentration varies. In this study, we proposed GaN-based blue LD structures with nonuniform doping distributions in the p-AlGaN cladding layer to reduce the modal loss and demonstrated improved efficiency characteristics using numerical simulations. We compared the laser power, operation voltage, and wall-plug efficiency (WPE) of LDs with uniform, linear, and quadratic doping profiles in the p-AlGaN cladding layer. As the doping concentration becomes increasingly inhomogeneous, the laser output power increases significantly because of the reduced overlap of the laser mode with the p-AlGaN cladding layer. However, this nonuniform doping profile also leads to an increase in the operation voltage due to the expansion of the low-doping region. By optimizing the nonuniform doping distribution in the p-type cladding layer, the WPE was found to be improved by over 5% compared to a conventional uniformly doped p-cladding layer. The proposed design of LD structures is expected to enhance the efficiency of high-power GaN-based LDs.