Improved light output characteristics of GaAs/InAs short-period superlattice quantum dot light emitting diodes by the insertion of InAlAs current blocking layer and laser operation

High lateral density (∼10¹¹ cm^-2) and well-aligned quantum dot (D) structures are self-formed in (GaAs)₂(InAs)_n short period superlattices grown on InP [411] substrates by gas source molecular beam epitaxy. Light emitting diodes with these Ds as an active layer were fabricated. However, in the light output versus driving current curves, the output intensity showed saturation for the driving current of over 100 mA. This saturation is considered to be due to the current overflow (electron overflow) through the heterojunction between D active layer and cladding layer. To overcome this problem, an InAlAs layer was inserted between D active layer and p-type cladding layer as a current blocking layer. As a result, no saturation of output power was observed up to 200 mA. Furthermore, laser diodes with these Ds as an active layer were fabricated and current injection laser operation was realized.