Heat treatment in 110 °C liquid water used for passivating silicon surfaces

The simple passivation method of heat treatment in liquid water is discussed. Photo-induced effective minority carrier lifetime τ eff increased to 3.3 × 10−3 s above 110 °C for 1 h for 17-Ωcm n-type crystalline silicon. Increase in τ eff was observed ranging from 3.5 × 10−4 to 3.7 × 10−3 s for n-type silicon with resistivity ranging from 2 to 17 Ωcm. τ eff maintained high values ranging from 1.5 × 10−4 to 1.4 × 10−3 s for 1270 h. The metal-insulator-semiconductor-type diodes were formed on the top surfaces of the n-type and p-type substrates by forming Al and Au metals on the 0.7-nm-thin passivated layers. Rectified and Fowler–Nordheim current characteristics were observed in the dark field because of the difference of the work function between Al and Au. High photo-induced current density of 31.1 mA/cm2 and photovoltaic effect were observed in case of light illumination of AM 1.5 at 100 mW/cm2 to the rear surface. The recombination velocity in the regions under the metal electrode in the MIS structure was determined by lateral diffusion of photo-induced carriers. They were 1000 and 11,000 cm/s under Al and Au, respectively, in the n-type Si substrate.