By using deep-level transient spectroscopy, combined with secondary-ion mass spectroscopy and capacitance-voltage profiling, it was demonstrated that Li diffusion into Au-doped n-type samples at temperatures of between 200 and 300C resulted in the formation of two Li-Au complexes. One of these complexes appeared to be electrically passive, and was observed indirectly as Au acceptor passivation. It was noted that nearly all of the passivated Au acceptors were reactivated after annealing (400C, 0.5h) samples with comparable Au and Li concentrations; which were of the order of 1014/cm3. The process could be reversed again by further heat treatment at lower temperatures. The passivation-reactivation cycle could be repeated as long as there was enough Li in the crystal. This reaction could be described by a mass-action law involving negatively charged Au atoms and positively charged Li (Au- + Li+) with a free binding energy of about 0.87eV. The other Au-Li complex had a deep level (L1), within the Si band-gap, with an activation energy of 0.41eV. The L1 signal was strongest after annealing at temperatures of between 250 and 300C, but was weaker at lower temperatures where the electrically passive Au-Li complex was favored. On the basis of the dissociation kinetics of L1 during reverse bias annealing, it was deduced that the complex consisted of one Au atom and one or more Li atoms. By using deep-level transient spectroscopy depth profiling, it was also observed that the injection of H into the surface region by wet chemical etching resulted in deactivation of the L1 trap.

E.O.Sveinbjörnsson, S.Kristjansson, H.P.Gislason: Journal of Applied Physics, 1995, 77[7], 3146-54