The recovery at room temperature of neutron-irradiated (average neutron energy 9.8 MeV) AlGaN/GaN high electron mobility transistors was studied by monitoring the electrical properties for a month. The initial changes in dc characteristics of the devices after neutron irradiation are consistent with the removal of free carriers by creation of deep levels in the bandgap. However, this lattice-displacement damage is unstable at room temperature and a self-annealing effect is observed. At a dose of 5.49x10(11) neutron/cm(2), the degradation of device drain-source current and transconductance was maximized one week after exposure to the neutron flux and was completely recovered three weeks after the irradiation.