GaN-based ultraviolet vertical-cavity surface-emitting lasers operating under room-temperature continuous-wave current injection

Abstract

GaN-based vertical-cavity surface-emitting lasers (VCSELs) have garnered considerable interest in recent decades, particularly in the blue-to-green spectral range. However, hindered by issues such as high optical absorption losses and inefficient thermal dissipation, the achievement of electrically injected ultraviolet (UV) VCSELs remains a challenge. In this study, to reduce the optical loss and enhance the gain of the active region, the device structure introduces a relatively thin, ∼20 nm, indium tin oxide current spreading layer and an optical adjustment layer of HfO2. Moreover, B+ implantation was employed to form a current confinement layer, replacing the conventional SiO2 layer, and an electroplated copper plate was used as a thermal sink, yielding a low thermal resistance of 209 K/W. Therefore, lasing of a GaN-based UV VCSEL was achieved at a wavelength of 380.1 nm and a threshold current density of 14.9 kA/cm2 under continuous-wave electrical injection for the first time to the best of our knowledge.