The indiffusion of Zn into InGaAsP layers was studied using a MOVPE-based diffusion process. Hydrogen and nitrogen were alternatively employed as carrier gas to compare their effect on the diffusion behaviour. Using nitrogen, larger diffusion coefficients of Zn were obtained under comparable conditions. Whereas in InGaAs, maximum hole concentration levels of > 1 x 10(20) cm(-3) were obtained for both N-2 and H-2, i.e. a factor of 3-4 higher than achievable with MOVPE doping, there proved to be no enhanced doping effect in InP. As to the lateral diffusion uniformity superior results were obtained with nitrogen.