Modification of the structural lattice parameters and electron spectra of n-GaAs films on sapphire on irradiation with reactor neutrons

Abstract

Changes in the structural parameters of epitaxial GaN films on sapphire (n-GaN/Al2O3(0001)) induced by irradiation with reactor neutrons with integrated fluences up to 7.25 × 1019 fn cm−2 (φfn/φtn ≈ 1) and subsequent isochronal annealing at temperatures up to 1000°C are studied. Measurements of the lattice parameters a and c of the irradiated n-GaN films show that the parameter c increases by 0.38% and the parameter a remains almost unchanged. From theoretical estimations, it follows that, in the irradiated n-GaN film, the elastic tensile stress along the c axis is as high as ∼1.5 GPa, whereas the compression stress in the basal plane of the unit cell is about −0.5 GPa. The tension of the irradiated GaN film along the hexagonal axis induces a decrease in the band gap Eg by 37 meV and a lowering of the charge neutrality level by 22 meV with respect to the corresponding parameters in the initial GaN film on sapphire. The parameter c changed by irradiation with reactor neutrons by Δc can be recovered by annealing in the temperature range 100–1000°C, with the basic stage of annealing at about 400°C.