A non-degenerate four-wave mixing technique has beenapplied to investigate carrier transport and recombination inheavily C-doped GaAs embedded in a double-heterostructure.The carriers were injected into the 1 µm-thickp-GaAs layer via the 50 nm-thick barrier ofAlGaAs:C or InGaP:Si, using the light interferencepattern of two picosecond laser pulses at 532 nm. Thedependence of the nonequilibrium carrier grating decay time on thegrating period allows the determination of minority carrierdiffusion coefficients: D = 35 cm2/s for p-GaAs( $p_0 = 2 \times 10^{19}$  cm−3) with AlGaAsbarriers and D = 27 cm2/s for p-GaAs ( $p_{0} =1 \times 10^{19}$  cm−3) with InGaP barriers. Thisincrease of electron mobility at the higher doping level was foundto be in agreement with the decreasing role of carrier-carrierscattering in heavily-doped p-GaAs. The fast recombinationof nonequilibrium carriers in the vicinity of a front barrierlayer was evident and more pronounced for an AlGaAs thanfor an InGaP barrier.