Silicon Surface Passivation by Organic Monolayers:  Minority Charge Carrier Lifetime Measurements and Kelvin Probe Investigations

• Published in: The journal of physical chemistry. B Vol. 107; no. 28; pp. 6846 - 6852
• Main Authors: Sieval, Alexander B, Huisman, Carolien L, Schönecker, Axel, Schuurmans, Frank M, van der Heide, Arvid S. H, Goossens, Albert, Sinke, Wim C, Zuilhof, Han, Sudhölter, Ernst J. R
• Format: Journal Article
• Language: English
• Published: American Chemical Society 17.07.2003
• Subjects: air; alkyl monolayers; germanium surfaces; hydrogen-terminated silicon; photoconductance decay; recombination velocity; si surface; si surfaces; si-sio2 interface; ultrathin sio2 overlayers
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp034314v

The silicon surface passivation of monolayers of organic compounds that are bound to Si surfaces by a covalent Si−C bond has been investigated. The effective lifetime τeff of minority charge carriers in the surface-modified semiconductor has been determined by modulated free carrier absorption (MFCA) measurements. The results show that on 1−2 Ω·cm p-type Si(100) surfaces modified with a monolayer obtained from CH2CH(CH2)8C(O)OCH3 maximum effective lifetimes τeff ≥ 130 μs can be obtained. This value corresponds to a maximum surface recombination velocity S eff of 120 cm/s, a value that is similar to those obtained using other passivation techniques, which demonstrates that these monolayers provide an interesting alternative for silicon surface passivation. During these MFCA measurements an unusual time dependence of the effective lifetime is observed:  τeff rises continuously during illumination of the substrate. Kelvin probe measurements show that there is a slow shift of the Fermi level of the semiconductor under illumination, which seems to be the result of a slow, reversible filling of surface traps.