Optical manipulation of nebulizer spray pyrolysed ZnS thin films for photodetector applications: Effect of Al, Sn and Sb doping

Abstract

Abstract In this work, we report the structural, morphological, optical and photo-sensing properties of pure as well as Al, Sn and Sb-doped ZnS thin films, with the prospect of photo-sensing and photo-detection applications. ZnS, ZnS:Al(1%), ZnS:Sn(1%) and ZnS:Sb(1%) thin films are fabricated by the spray pyrolysis method. These thin films exhibit polycrystalline nature and crystallize in hexagonal wurtzite ZnS structure. Optical properties reveal the semiconductor behavior of all the films. The optical bandgap (Eg) values, which are around 3.67 eV, 3.43 eV, 3.32 eV and 3.56 eV for ZnS, ZnS:Al(1%), ZnS:Sn(1%) and ZnS:Sb(1%) thin films, respectively, decrease with Al, Sn and Sb-doping. On the other hand, doping of Al, Sn and Sb into the ZnS lattice enhances the photo-sensing parameters such as responsivity (R) and external quantum efficiency (EQE). Al-doping into the ZnS does not affect detectivity (D*) but Sb-doping results in a decrement of D*-value. ZnS:Sn(1%) photo-detector exhibits the highest R, EQE and D*-values of 1.05 × 10−1 AW−1, 33.9% and 4.29 × 1010 Jones, respectively, among all the fabricated photo-devices. Thus doping of post-transition (Al, Sn) and metalloid (Sb) elements into the ZnS host lattice significantly alter the optical and photo-sensing properties of the present thin films.