InGaN green laser diodes with grade p-AlGaN cladding layer

Distributed polarization-doped (DPD) AlGaN cladding layer (CL) has been successfully used in AlGaN ultraviolet laser diodes (LDs), which overcomes the problem of low Mg doping efficiency and can reduce the internal loss of LDs. However, this graded AlGaN CL is rarely used in InGaN visible LDs. Our previous work reported green LDs with DPD AlGaN CL, which can reduce the threshold current density of LDs, but suffer from the problem of low slope efficiency, only 0.07 W/A. Therefore, LDs with different structures were analyzed by optical field and device simulation. It was found that the electron blocking layer (EBL) in the LD structure is necessary to hinder electron leakage, even if a graded AlGaN CL with a high initial Al composition is used. By adopting an EBL, the slope efficiency of LDs with DPD AlGaN CL increased to 0.54 W/A, while the threshold current density was only slightly increased and the operating voltage was significantly reduced, compared with our previous report. These green LDs with DPD AlGaN CL also show a better performance than traditional green LDs.