Study of intrinsic point defects in γ-In2Se3 based on first principles calculations for the realization of an efficient UV photodetector

In2Se3 have attracted researcher’s attention due to its potential optoelectronic and memory device applications, having various polymorphs with few of them having layered structure. There exists a non-layered phase with vacancy ordered in screw form known as γ-In2Se3, whose properties are found to get affected majorly by the presence of defects. Here, the first principles calculations based on the density functional theory are performed to study the intrinsic point defects in defect wurtzite structure of γ-In2Se3 using GGA-PBE approximations. Thermodynamic charge transitions based on the formation energy of the defects are determined for all native defects, VIn, VSe, Ini, Sei, SeIn, InSe, under In-rich and Se-rich experimental growth conditions. The charge transition remains the same but transition energies differ for possible coordination of Se vacancies, whereas the charge transition as well as transition energy vary for different coordination sites of In vacancies. The In interstitial, Ini is the most favourable defect site under In-rich conditions whereas SeIn at the VBM and VIn1 near CBM are dominating under Se-rich conditions. The origin of n-type conductivity of γ-In2Se3 is found to be the presence of Ini interstitials and InSe antisite in the defect wurtzite γ-In2Se3. Further, the films grown using PLD shows an n-type conductivity under In-rich conditions leading to a good performance with photo responsivity and specific detectivity of 5.22 × 102 A/W and 5.08 × 1013 Jones. The understanding of these vacancies determines their thermodynamic behaviour which can help for the controlled growth of γ-In2Se3 which leads to better device performance.