Impact of Antisite Defect Complex on Optical and Electrical Properties of Ag 2 ZnSnSe 4 Thin Films

Herein, preparation of Ag 2 ZnSnSe 4 (AZTSe) thin films using physical vapor deposition followed by selenization in a quartz tube with rapid thermal process (RTP) is reported. The precursor stacks, [Sn/Se/ZnSe/Se/Ag/Se] × 4, are deposited onto the glass substrate at 100 °C using the combination of thermal and e‐beam evaporation methods. The post selenization of precursors is conducted at different temperatures (300–425 °C). The X‐ray diffraction and Raman spectra of the precursor films selenized at 400 °C reveal the formation of single‐phase AZTSe, exhibiting a kesterite structure with a preferred orientation along the (112) plane. These films show larger grains of ≈230 nm with the homogeneous distribution of Ag, Zn, Sn, and Se across the film thickness. The precursor films selenized at temperatures ≤400 °C show the fundamental absorption edge of AZTSe ( E g  = 1.36–1.44 eV) as well as an additional adsorption edge ( E add  = 1.31–1.32 eV) corresponding to Zn Sn  + Sn Zn defect complex. The Hall effect measurement indicates n‐type conductivity irrespective of selenization temperature. For films selenized at 400 °C, the carrier concentration is decreased to 2.83 × 10 11  cm −3 and results in a high mobility of 73.9 cm 2 (V s) −1 , which is attributed to the reduction of Sn Zn defects.