A diffusion time-of-flight (TOF) technique is described and analysis is performed on four different p-GaAs heterostructure devices. These p/n junction devices were grown by metal organic chemical vapor deposition (MOCVD). Both Zn and Mg were used as dopants with concentrations ranging from 1×1018 to 1×1019 cm−3. We have been able to determine the diffusivity (D) along with upper and lower estimates of the diffusion length (LD). The results imply the presence of a mechanism such as photon recycling.