Experimental results show that the background carrier concentrations in GaN films grown by metalorganic vapor phase epitaxy are related to defects. A thermal equilibrium method was used to calculate the background carrier concentration related to intrinsic defects in an ideal GaN crystal. The results show that the N vacancy concentration does not exceed2×1017 cm−3in GaN grown at temperatures ranging from 800 to 1500 K. It can be concluded that the N vacancy is one of the major sources of carriers when the carrier concentrationn<2×1017 cm−3,but the main sources should be other defects whenn>2×1017 cm−3;this conclusion may lead to ways for further improving the quality of GaN films. ©1997 American Institute of Physics.