Enhancement of optical confinement factor by InGaN waveguide in blue laser diodes grown by plasma-assisted molecular beam epitaxy

Abstract

The influence of InxGa1−xN waveguide on the properties of blue (λ = 450 nm) laser diodes grown by plasma-assisted molecular beam epitaxy was studied. The threshold current density was reduced by 50% (to 3.6 kA/cm2) when the indium content was increased from x = 0.04 to 0.08. This is explained by a substantial enhancement of the optical confinement factor for a high-In-content waveguide, which increases the differential modal gain. Furthermore, we observed a decrease in optical losses when Mg-doped layers were separated from the active region by a thicker waveguide. This is attributed to the lower overlap between the optical mode and absorptive Mg-doped layers.