Minority Carrier Lifetime Behavior in Crystalline Silicon in Rapid Laser Heating

We report changes in the light-induced minority carrier effective lifetime tau(eff) of crystalline silicon caused by rapid laser heating. The top surface of n- and p-type silicon substrates with thicknesses of 520 and 150 mu m coated with thermally grown SiO2 layers were heated by a 940nm semiconductor laser for 4ms. tau(eff) was measured by a method of microwave absorption caused by carriers induced by 620nm light illumination at 1.5mW/cm(2). tau(eff) for light illumination of the top surfaces was decreased to 1.0 x 10(-5) and 4.8 x 10(-6) s by laser heating at 5.0 x 10(4) W/cm(2) for nand p-type 520-mu m-thick silicon substrates, respectively. It was decreased to 1.5 x 10(-6) and 6.7 x 10(-6) s by laser heating at 4.2 x 10(4) W/cm(2) for n- and p-type 150-mu m-thick silicon substrates, respectively. The decrease in tau(eff) resulted from the generation of defect states associated with the carrier recombination velocity at the top surface region, Stop. Laser heating increased Stop to 6000 and 10000 cm/s for n- and p-type 520-mu m-thick silicon substrates, respectively and to 9200 and 2150 cm/s for n- and p-type 150-mu m-thick silicon substrates, respectively. Heat treatment at 400 degrees C for 4 h markedly decreased S-top to 21 and 120 cm/s respectively for 520-mu m-thick n- and p-type silicon samples heated at 5.0 x 10(4) W/cm(2). The heat treatment also decreased, 10 and 35 cm/s, respectively, for 150-mu m-thick n- and p-type silicon substrates heated at 4.2 x 10(4) W/cm(2). (C) 2012 The Japan Society of Applied Physics