Luminescence of insulator layers on silicon excited by electrons

Abstract

We present a comparative analysis of cathodoluminescence (CL) and electroluminescence (EL) spectra measured on Si–SiO₂ and Si–Ta₂O₅ structures with various thicknesses of insulator layers. Spectral distribution of luminescence depends on how the insulator layer was formed, its thickness and type of excitation. The analysis indicates that CL and EL spectra of Si–SiO₂ structures, grown by thermal oxidation of silicon in “dry” oxygen, are almost identical in spectral composition. Based on the dependence of intensity of the luminescence band with a maximum at energy of 2.2 eV, it was concluded that the corresponding luminescence centers are uniformly distributed over the oxide layer thickness in the range of 30–200 nm. It is assumed that these luminescence centers are oxygen vacancies formed during the thermal oxidation of silicon. In the case of Ta₂O₅ layers on silicon, the presence of defects (luminescence centers) in the oxide layer leads to the formation of a set of energy levels in the band gap of the Ta₂O₅ layers obtained by ALD. They appear in the luminescence spectra regardless of the excitation method.