A method of modelling heterojunction acoustic charge transport (HACT) in GaAs has been developed. This model allows for nonuniform impurity doping profile, variable epitaxial layer configuration, and arbitrary structural design of the input electrode. The acoustic wave potential is incorporated as a time- and space-varying doping density that adds directly to the impurity doping density. The wave-induced doping density is obtained from the piezoelectric displacement charge that accompanies the acoustic wave. The method uses a solution of the two-dimensional Poisson equation to obtain the potential and charge distribution in the charge injection region of an HACT device.