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

Abstract

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 CH2CH(CH2)8C(O)OCH3 maximum effective lifetimes τeff ≥ 130 μs can be obtained. This value corresponds to a maximum surface recombination velocity Seff 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 semiconduct...