Improvement of the performance characteristics of deep violet InGaN multi-quantum-well laser diodes using step-graded electron blocking layers and a delta barrier

The performance characteristics of deep violet In_0.082Ga_0.918N/GaN multi-quantum-well (MQW) laser diodes (LDs) with step-graded electron blocking layers (EBLs), a new EBL structure proposed by Zhang et al. and Yang et al., were numerically investigated. The simulation results indicated that the output emission wavelength was blue-shifted because of the change in the built-in polarization and internal electric field, although the use of step-graded EBLs effectively improved LD performance. To prevent the polarization effects and consequently a blue shift in the output emission wavelength, a new MQW LD structure with step-graded EBLs and a delta barrier as a last barrier is proposed. Simulation results indicated that the proposed LD structure exhibits higher values of output power, slope efficiency, and differential quantum efficiency, as well as lower threshold current, compared with conventional LD structures. The results also showed that the use of the delta barrier reduced the changes in the built-in polarization and internal electric field, and negligible changes in the output emission wavelength were observed.