Effect of thermal annealing on the properties of narrow-bandgap ZnSnAs2 epitaxial films on InP(001) substrates

ZnSnAs2 epitaxial film has been grown on epi-ready semi-insulating InP(001) substrates by low-temperature molecular beam epitaxy (LT-MBE) technique. The MBE-grown sample was then cleaved into pieces, three of which were subjected to lowtemperature annealing at different temperatures of 300 ∘C, 320 ∘C and 340 ∘C which are equal or slightly higher than growth temperature using face-to-face proximity capping by GaAs wafers to simulate arsenic atmosphere. HR-XRD measurements showed that increasing annealing temperature decreases the lattice constant towards the bulk value. This suggests that indeed the relatively higher lattice constant of ZnSnAs2 epitaxial films is partly, if not wholly, due to defects consequence of low temperature growth. For the as-grown control sample, resistivity of 4.31×10−2 Ω cm, mobility of 17.7 cm2/V −s and hole concentration of 8.18×1018 cm−3 were obtained at room temperature. After annealing at 340 ∘C, the resistivity was increased to 21.0×10−2 Ω cm, the mobility increased to 60.9 cm2/V −s, and the hole concentration was decreased to 4.88×1017 cm−3.