Substitutional (B, P, As, Ga) and interstitial (K) dopants were incorporated into H-free amorphous films that had been produced by the ion beam amorphization of crystalline Si. Photo-thermal deflection spectroscopy, electronic transport and X-ray absorption fine-structure measurements were performed in order to monitor annealing-induced ordering phenomena around implanted dopant impurity sites. It was found that, in thermally relaxed amorphous material, substitutional dopant impurities had a marked tendency to enter the random network in the form of threefold-coordinated electrically-inactive sites. It was shown that the bonding constraints that were associated with these sites retarded structural relaxation of the amorphous films and crystallization of the amorphous network in the immediate neighborhood of these sites. In agreement with previous work, it was found that high defect-density films could be electrically doped with interstitial K. In such interstitially doped material, excess dangling-bond densities were observed which were likely to arise from a charge-induced bond-breaking mechanism.

G.Müller, W.Hellmich, G.Krötz, S.Kalbitzer, G.N.Greaves, G.Derst, A.J.Dent, B.R.Dobson: Philosophical Magazine B, 1996, 73[2], 245-59