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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.