Characteristics of thermo- and photo-stimulated electron emission from silicon wafers

Abstract

The temperature dependence of photoelectric emission and its spectral yield has been studied for Si (100) wafer surfaces with a native oxide film. The emission measurement was performed using a gas-flow Geiger counter developed for examining real surfaces. The saturation emission observed as a function of temperatures between 26 and 350 °C under illumination with far ultraviolet rays had the average activation energy of 0.27 eV in the Arrhenius plot. The analysis of the spectral yield observed after the preillumination gave two almost temperature independent photoelectric thresholds of 4.84 ± 0.11 and 5.57 ± 0.15 eV. The difference between the former value and the indirect optical excitation threshold for a clean, cleaved silicon surface reported by Gobeli and Allen approximately agrees with the activation energy. This energy is interpreted as being due to a thermal process for electron transport from the silicon substrate to the SiO2/Si interface states. A new emitting center with optical activation energy of about 5.7 eV was also found for the preilluminated surfaces. Copyright © 2008 John Wiley & Sons, Ltd.