Index-antiguiding in narrow-ridge GaN-based laser diodes investigated by measurements of the current-dependent gain and index spectra and by self-consistent simulation

TL;DR

This paper investigates index-antiguiding effects in narrow GaN-based laser diodes through experimental measurements and self-consistent simulations, revealing how etch depth influences threshold current and far-field patterns.

Contribution

It introduces a combined experimental and simulation approach to quantify and model index-antiguiding in narrow GaN laser diodes, emphasizing the role of etch depth.

Findings

Experimental antiguiding factor R = 10 near threshold

Shallow ridge etch depth affects threshold current and far-field pattern

Self-consistent simulations match experimental results when including antiguiding effects

Abstract

The threshold current density of narrow (1.5 {\mu}m) ridge-waveguide InGaN multi-quantum-well laser diodes, as well as the shape of their lateral far-field patterns, strongly depend on the etch depth of the ridge waveguide. Both effects can be attributed to strong index-antiguiding. A value of the antiguiding factor R = 10 is experimentally determined near threshold by measurements of the current-dependent gain and refractive index spectra. The device performances are simulated self-consistently solving the Schr\"odinger-Poisson equations and the equations for charge transport and waveguiding. Assuming a carrier-induced index change which matches the experimentally determined antiguiding factor, both the measured high threshold current and the shape of the far-field pattern of lasers with shallow ridges can be reproduced theoretically.