Highly uniform characteristics of blue-violet lasers on a 3-inch φ wafer

Blue-violet lasers with highly uniform characteristics have been realized on a 3-inch phi sapphire substrate. Epitaxial lateral overgrowth (ELO) is adopted in order to reduce the dislocation density of the GaN-layer. The wing region from the seed layer to the coalescence region was extended to over 6 mum, while the ELO-GaN layer was maintained at approximately 5 mum so as to minimize wafer bending. This process allows the laser stripe to be aligned reproducibly in the low-dislocation region of the ELO substrate. The layer thickness and wavelength varied within +/-5% and +/-2.5 nm, respectively, and the threshold current of the lasers was centered around 31.3 mA with a standard deviation of only 2.8 mA.