100?m-Cavity GaN-Based Edge Emitting Laser Diodes by the Automatic Cleavage Technique Using GaN-on-Si Epitaxial Lateral Overgrowth

We propose a novel laser diode (LD) fabrication process that yields 100 mu m-cavity GaN-based edge emitting LDs with cleaved facets. In this process, epitaxial layers for LDs are grown on a Si substrate, with a GaN layer grown using the epitaxial lateral overgrowth (ELO) technique. The ELO is finished before coalescence, resulting in multiple stripes. This configuration generates tensile stress in the direction parallel to the stripes, which originates from the difference between the thermal expansion coefficients of GaN and Si. This anisotropic tensile strain realizes automatic cleavage for laser facets without a breaking process. An array of dies manufactured through automatic cleavage are selectively transferred to a submount wafer, which is attributed to the weak connection of the ELO layers with the growth restriction mask. This wafer-level transfer technique enables the handling of tiny dies incorporating facet coating processes. The unique shape of the ELO layer, which is extremely thin and narrow in width, enables cleavage with a cavity length shorter than that of the conventional process. The fabricated device yielded lasing at 83 kA/cm2. This fabrication process can realize unique III-nitride LDs that exhibit low energy consumption for mobile applications such as augmented-reality glasses.

Automated summary

We propose a novel laser diode fabrication process to produce GaN-based edge emitting LDs with a cavity length of 100 mu m and cleaved facets. The process involves growing epitaxial LD layers on a Si substrate using the epitaxial lateral overgrowth (ELO) technique. The unique configuration of the ELO layers generates anisotropic tensile strain, enabling automatic cleavage of the laser facets without a breaking process. This fabrication process has the potential to create low energy consumption III-nitride LDs for mobile applications like augmented-reality glasses.