Path-robust quantum-well-width responses and wavelength-dependent wide-well efficiency recovery in InGaN laser diodes

A self-consistent two-dimensional LASTIP model is used to compare, under fixed model parameters, the well-width responses of 382- and 450-nm InGaN double-quantum-well laser diodes. Two constraints are considered: a fixed threshold wavelength and a fixed In composition. Although the two paths follow different trajectories in the well-width-material-state space, the main well-width trends remain robust against the path choice, whereas the quantitative performance and exact extrema remain path dependent. A microscopic comparison along the fixed-threshold-wavelength path shows stronger excited-state participation with increasing well width in both wavelength bands. However, wide-well efficiency recovery appears at 450 nm but not at 382 nm. Further analysis indicates that excited-state participation alone is not sufficient for wide-well efficiency recovery: the two bands exhibit different total modal-gain spectral responses, as well as quantitative differences in the changes in the above-threshold incremental stimulated-recombination fraction and differential external quantum efficiency. Thus, while the main well-width trends can remain consistent under different constraint paths, the optimum well width depends on the constraint path and the selected metric. Moreover, the wide-well efficiency-recovery advantage cannot be unconditionally extrapolated to low-In, short-wavelength devices.