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A novel deep-ridge laser structure with atomic-layer deposition (ALD) sidewall passivation was proposed that enhances the optical characteristics of 8-µm ridge width III-nitride violet lasers on freestanding m-plane GaN substrates. The internal loss was determined using the variable stripe length method, where the laser structure with ALD sidewall passivation showed lower internal loss compared to the conventional shallow-ridge laser design. ALD sidewall passivation plays a critical role in device improvements; compared to the lasers without ALD sidewall passivation, the lasers with ALD sidewall passivation yield improved optoelectrical performance and longer lifetime under continuous-wave operation at high current density. This work demonstrates the importance of ALD sidewall passivation to laser performance, which enables high energy efficiency.

A nonpolar edge emitting thin film InGaN laser diode has been separated from its native substrate by mechanical tearing with adhesive tape, combining the benefits of Epitaxial Lateral Overgrowth (ELO) and cleavability of nonpolar GaN crystal. The essence of ELO is mainly to weakening strength between native substrate and the fabricated laser device on top of it. We report a 3 mm long laser bar removed from its native GaN substrate. We confirmed edge emitting lasing operation after cleaving facets on a separated thin bar. Threshold current density of the laser was measured to be as low as 2.15 kA/cm 2 .