Enhancement of Electro-Optical Characteristics in GaN-Based Ultraviolet Laser Diodes Through Upper Optical Confinement Structure Design

Two series of laser diodes with different AlGaN cladding layers were investigated, and it was found that the internal absorption loss was reduced by using a u-AlGaN and p-AlGaN composite upper cladding layer, and the performance of LD was improved. The optimized thickness of u-AlGaN is related to the waveguide layer structure of LDs. For LDs with a thick waveguide layer, the u-AlGaN cladding layer should be thinner to achieve high hole concentration and high hole injection efficiency. For LDs with a thin waveguide layer, the u-AlGaN cladding layer can be thick to suppress the internal absorption loss. Thus, a composite upper waveguide structure with a thinner waveguide layer, a thicker u-AlGaN cladding layer, and a p-AlGaN cladding layer is an optimized structure for short waveguide UV LDs due to lower carrier loss and absorption loss.