Record performance Near-IR (765 nm) AlAs/AlGaAs VCSELs

Abstract

We have fabricated AlAs/AlGaAs Vertical Cavity Surface Emitting Lasers (VCSELs) emitting at 765 nm with record performance. The VCSELs were fabricated using MOVPE and a combination of dry and wet etching for the lateral structuring of the laser posts. Minimum threshold currents of 600 μA and threshold voltages of 1.9 V are achieved for VCSELs with a mesa diameter of 26 μm. The maximum slope efficiencies are 0.46 W/A with wallplug efficiencies of 11.2 % at an output power of 1 mW. The maximum output powers for larger devices exceed 5 mW. To our knowledge these are the best performance characterstics for VCSELs operating in the 760 - 780 nm wavelength range. Compared to recently published data on 780 nm VCSELs in the GalnAsP/AlGalnP material system, the threshold currents ate more than a factor of 4 smaller, the wallpug efficiencies are a factor of 1.7 larger. We attribute the high performance to the accurate control over growth rates and aluminum contents, the layer design and the improved lateral current confinement by an additional lateral selective etching step. Spectral measurements show that the lasers operate single transverse mode over a wide current range with single mode output powers above 1 mW. A comparison with conventional mesa-etched VCSEL structures is made to demonstrate the impact of the additional lateral etching step on the device performance.