Milliwatt‐class GaN‐based blue vertical‐cavity surface‐emitting lasers fabricated by epitaxial lateral overgrowth

Abstract

We have achieved continuous‐wave (CW) operation of gallium nitride (GaN)‐based vertical‐cavity surface‐emitting lasers (VCSELs) fabricated by epitaxial lateral overgrowth (ELO) using dielectric distributed Bragg reflectors (DBRs) as masks for selective growth. The GaN VCSELs exhibited CW operation at a wavelength of 453.9 nm, and the maximum output power was 1.1 mW, which is the highest value reported to date. GaN‐based materials have presented challenges for obtaining DBRs with high reflectivity and a wide stopband, precise control of the cavity length and a lateral confinement structure to provide laser operation. The proposed VCSEL is immune to these concerns. Its two dielectric DBRs were obtained free from cracks. A high reflectance of more than 99.9% and a stopband with a width of 80–97 nm were obtained for both DBRs. The cavity length was controlled by epitaxial growth to as short as 4.5 µm. An ITO contact electrode on p‐type GaN, which is required for a lateral confinement structure, showed electrical reliability under a high current density of 59.6 kA cm−2. The present data demonstrate that the fabrication process adopted here overcomes the shortcomings that have prevented the widespread use of GaN‐based VCSELs.