Effect of the doping level of a p-cladding layer on the performance of GaAs-AlGaAs multiquantum-well lasers

CW performance of multiquantum-well (MQW) GaAs-AlGaAs lasers operating near 850 nm at 300 K is investigated as a function of the doping level in the p-cladding layer. Laser structures have been grown by metal-organic chemical vapor deposition using Zn diethyl as a carrier for acceptor dopant. An undoped sublayer (setback) has been introduced to separate the heavily doped part of the cladding from the mode volume. The doping level of zinc ranges from 4×10¹⁷ to 6.5×10¹⁸cm^-3. Along with this increase of the doping level, the threshold current density increases from 370 to 612 A/cm² whereas the slope efficiency of the laser increases from 0.71 to 1.33 W/A with an improvement of the characteristic temperature constant T₀ from 150 to 250 K. At the highest level of doping, the internal quantum yield is found to be close to unity and optical losses are as low as 1.36 cm^-1. An increase of the stable single-mode output is also obtained in 3-μm-wide ridge-waveguide diodes up to ∼180 mW.