Cyanide treatment which simply involves immersion of semiconductors in cyanide solutions can passivate interface states as well as surface states. When Si surfaces are treated with KCN solutions, a surface photovoltage greatly increases, and the surface recombination velocity is calculated to be decreased from ∼3000 cm/s to less than 200 cm/s. When the cyanide treatment is applied to ultrathin SiO 2 /single-crystalline Si structure, interface states are passivated. The passivation of the SiO 2 /Si interface states increases the energy conversion efficiency of 〈indium tin oxide (ITO)/SiO 2 /Si〉 MOS solar cells to 16.2% and decreases the leakage current density for 〈aluminum (Al)/SiO 2 /Si〉 MOS diodes to 1/3-1/8. When the cyanide treatment is performed on polycrystalline (poly-) Si, defect states in Si up to at least 0.5 μm depth from the surface are passivated, resulting in a vast increase in the energy conversion efficiency of 〈ITO/SiO 2 /poly-Si〉 solar cells and a decrease in the dark current density of 〈Al/SiO 2 /poly-Si〉 MOS diodes to 1/100-1/15 that without cyanide treatment. The defect passivation is attributed to the formation of Si-CN bonds from defect states. Si-CN bonds are found not to be ruptured by heat treatment at 800°C and AM 1.5 100 mW/cm 2 irradiation for more than 1000 h. Density functional calculations show that the thermal and irradiation stability results from strong Si-CN bonds with the bond energy of 4.5 eV. When the cyanide treatment is performed on oxide/GaAs(1 0 0) structure, the interface state density decreases to ∼50%. The cyanide treatment can also passivate defect states in Cu 2 O films, resulting in increases in the carrier density and the band-to-band photoluminescence intensity.
|ジャーナル||Applied Surface Science|
|出版ステータス||Published - 2004 8月 15|
|イベント||Proceedings of 3rd International Workshop on Semiconductor - Ustron, Poland|
継続期間: 2003 9月 15 → 2003 9月 17
ASJC Scopus subject areas
- 化学 (全般)