Samples were irradiated with thermal neutrons (1.8 x 1017 or 1.8 x 1018/cm2). This introduced defects that markedly altered the semiconducting properties. By annealing the samples at 700C, it was found to be possible to annihilate the defects and restore the original properties.

K.H.Heckner, G.Majoros, A.Kraft, R.Landsberg: Physica Status Solidi A, 1995, 148[2], 407-12