The p+- and n+-Si channels were prepared by implanting a dose of 5×1015 ions/cm2 of BF2+ and As+ at 40 keV, respectively, into the n-Si and p-Si substrates, followed by a 900 °C-30 min annealing. Nickel contacts (cathode and anode) to these channels were electron-gun evaporated. Electrical current was applied gradually to 80 mA to these channels, corresponding to current densities of 106–107 A/cm2. For the p+-Si, the resistance responded by increasing to a maximum, then decreasing until a precipitous drop took place. For the n+-Si, the resistance increased by a less amount compared to the p+-Si, but also dropped abruptly. The resistance drop is permanent in the p+-Si channels, but not in the n+-Si channels. Mechanisms responsible for these resistance changes in terms of Joule heating, high field effect and junction leakage are proposed. For the precipitous drop in channel resistance of the p+-Si, scanning electron microscopy and transmission electron microscopy showed that a NiSi2 line bridging the cathode and anode contacts had been formed. No silicide line formation in the n+-Si channels was observed. © 1998 American Institute of Physics.