Effect of Aluminum Doping on the Nanocrystalline ZnS:Al³⁺ Films Fabricated on Heavily-Doped p-type Si(100) Substrates by Chemical Bath Deposition Method

Abstract

Intrinsic ZnS and aluminum-doped nanocrystalline ZnS (ZnS:Al³⁺) films with zinc-blende structure were fabricated on heavily-doped p-type Si(100) substrates by chemical bath deposition method. Influence of aluminum doping on the microstructure, and photoluminescent and electrical properties of the films, were intensively investigated. The average crystallite size of the films varying in the range of about 9.0 ∼ 35.0 nm initially increases and then decreases with aluminum doping contents, indicating that the crystallization of the films are initially enhanced and then weakened. The incorporation of Al³⁺ was confirmed from energy dispersive spectrometry and the induced microstrain in the films. Strong and stable visible emission band resulting from the defect-related light emission were observed for the intrinsic ZnS and ZnS:Al³⁺ films at room temperature. The photoluminescence related to the aluminum can annihilate due to the self-absorption of ZnS:Al³⁺ when the Al³⁺ content surpasses certain value. The variation of the resistivity of the films that initially reduces and then increases is mainly caused by the partial substitute for Zn²⁺ by Al³⁺ as well as the enhanced crystallization, and by the enhanced crystal boundary scattering, respectively.