Study of Er-related defects in a-Si : H(Er)/c-n-Si heterostructures by thermally activated current spectroscopy

Abstract

The paper is devoted to study of Er-related defects in electrical luminescence diode structures a-Si : H(Er)/c-n-Si, for which amorphous hydrogenated silicon film on crystalline Si substrate was fabricated both by plasma-enhanced chemical vapor deposition and magnetron-assisted silane-decomposition technique. Thermally activated current (TAC) spectroscopy by employing the thermally fractional cleaning method has been used. Observed TAC spectra have been shown to be weakly dependent on the film-deposited technique. It has been shown, that signal amplitude of the spectra increases, when Er concentration in a-Si : H increases. The traps with activation energies from 0.10 to 0.40 eV and from 0.5 to 0.6 eV have been charged both by light and thermal-bias stress, which allows to associate these with the deep levels in the band gap of the a-Si : H. The high-temperature current peaks with activation energies of 0.8–1.0 eV have been created only by thermal-bias stress and have been strongly dependent on the charging temperature. It has been suggested that these high-temperature thermally activated processes are related to polarization effects in the [Er–O] clusters, located in amorphous matrix of a-Si : H. The plausible origin of the observed deep levels and polarization processes is discussed.