The effect of neutron irradiation and annealing temperature on the electrical properties and lattice constant of epitaxial gallium nitride layers

Abstract

Effect of irradiation with high reactor-neutron fluences (Φ = 1.5 × 1017-8 × 1019 cm−2) and subsequent heat treatments in the temperature range 100–1000°C on the electrical properties and lattice constant of epitaxial GaN layers grown on an Al2O3 substrate is considered. It is shown that, with the neutron fluence increasing to (1–2) × 1018 cm−2, the resistivity of the material grows to values of about 1010 Ω cm because of the formation of radiation defects, and, with the fluence raised further, the resistivity passes through a maximum and then decreases to 2 × 106 Ω cm at 300 K, which is accounted for by the appearance of a hopping conductivity via deep defects in the overlapping outer parts of disordered regions. With the neutron fluence raised to 8 × 1019 cm−2, the lattice constant c increases by 0.38% at a nearly unchanged parameter a. Heat treatment of irradiated samples at temperatures as high as 1000°C does not fully restore the lattice constant and the electrical parameters of the material.