Observation of reduced current thresholds in GaAs/AlGaAs vertical-cavity surface-emitting lasers grown on 4° off-orientation (001) GaAs substrates

Abstract
GaAs/AlGaAs vertical‐cavity surface‐emitting lasers (VCSELs) with two semiconductor distributed Bragg reflectors (DBRs) were grown by molecular beam epitaxy. The threshold current was found to be 20–50% less on an average for VCSELs grown on the 4° off‐orientation (001) substrates than those on the on‐orientation ones. The lower threshold current was attributed to the smoother interfaces of the Al0.1Ga0.9As/AlAs DBRs in the off‐orientation growth observed by transmission electron microscopy. A threshold current and current density of 12 mA and 10.5 kA/cm2 were measured with an emission efficiency of 0.2 mW/mA.