Optical loss suppression in long-wavelength semiconductor lasers at elevated temperatures by high doping of the n-waveguide

We show that strong n-doping of the n-waveguide layer substantially decreases the thermal carrier leakage from the active layer and the associated optical losses in III-V semiconductor lasers. The effect is particularly pronounced in devices operating at the wavelength region where the free hole absorption cross-section is much greater than that of free electrons. This is predicted to decrease the threshold current and improve the output efficiency of the lasers. An example of bulk InGaAsP/InP pulsed lasers is used to demonstrate that lasers with a highly doped n-InGaAsP side of the waveguide can retain high output powers at ambient temperatures substantially above room temperature.