GaN blue vertical-cavity surface-emitting lasers using conductive nanoporous distributed Bragg reflectors

Abstract

Due to their unique properties, III-nitride vertical -cavity surface-emitting lasers (VCSELs) are expected to enable several applications ranging across communication, sensing and ranging and spectroscopy. Their technological feasibility however has been hindered by the lack of an electrically conductive, easily manufacturable, wide reflection stopband distributed Bragg reflector (DBR) to serve as the bottom reflector. Here we present the first electrically injected III-nitride VCSEL on an electrically conductive DBR using nanoporous (NP) GaN operating at roomtemperature. The measured threshold current density and the maximum light output power were 42 kA/cm² and 0.17 mW, respectively, at 434 nm. Due to the electrical conductivity of the bottom NP GaN DBR, vertical injection was demonstrated and compared with intracavity injection. No change in the threshold current density, the slope efficiency or nearfield pattern was observed demonstrating the feasibility of efficient vertical injection in NP GaN VCSELs. Filamentary lasing was observed within the VCSEL aperture and its correlation with the lasing linewidth was studied.