A study of two-dimensional electron gas distribution in AlGaN/GaN heterostructure field effect transistors is performed by solving the coupled Schrödinger’s and Poisson’s equation self-consistently. Taking the piezoelectric effect into account, the two-dimensional electron gas concentration is calculated to be as high as 1019 cm−3. To gain an understanding on how the two-dimensional electron gas distribution is influenced by dopant concentration in material, we observed the two-dimensional electron gas concentration and occupation of subbands versus doping level in GaN and in AlGaN layer. The results show that the two-dimensional electron gas concentration depends much more strongly on the doping level in AlGaN than in GaN. And besides, the heavier doping in GaN should weaken the quantum confinement in the AlGaN/GaN heterointerface. © 2001 American Institute of Physics.