科研之友
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摘要
We report decreases in the minority carrier effective lifetime t(eff) of 700-mu m-thick silicon substrates coated with 43-nm-thick thermally grown SiO2 layers by Ge ion implantation with a dose of 1 x 10(13) cm(-2) at 150 keV and rapid thermal annealing (RTA) at 1100 degrees C for 50 s. Ge ion implantation decreased the crystalline volume ratio in the top 157nm region because of lattice damage. It also markedly decreased t(eff) to 1: 6 x 10(-6) and 9: 5 x 10(-6) s when 635 and 980nm lights were continuously illuminated to the implanted surface, respectively. Small t(eff) values resulted from serious damage with a high surface recombination velocity S of 2: 0 x 10(4) cm/s and a short bulk lifetime of 5: 0 x 10(-6) s in the 200 mu m deep surface region. Although RTA successfully recrystallized the Ge-implanted surface region, it further decreased t(eff) to 1: 1 x 10(-6) and 2: 2 x 10(-6) s in the cases of 635 and 980nm light illuminations to the top surfaces, respectively. RTA caused a high density of recombination sites with a high S value of 3: 0 x 10(4) cm/s on the top and rear surfaces. There was a high density of interface traps of 9: 1 x 10(11) eV% 1cm% 2. 1: 3 x 10(6) Pa H2O vapor heat treatment at 260 degrees C for 3 h markedly increased t(eff) to 6: 5 x 10(-4) and 6: 9 x 10(-4) s in the cases of 635 and 980nm light illuminations. The interface trap density was decreased to 3: 6 x 10(10) eV% 1cm% 2. Low temperature post annealing is effective in curing the recombination defect states induced by RTA.
- 出版日期2014-6
