Electronic and optical properties of Te-doped GaN monolayer before and after adsorption of dimethylmercury - DFT+U/TDDFT & DFT-D2 methods.

Electronic, magnetic and optical properties of Te doped g-GaN monolayer, before and after adsorbing the dimethylmercury molecule, (CH3)2Hg, were studied by DFT approach. Our calculations show that, unlike pure g-GaN monolayer, the g-GaN + Te is n-type, in which the previous gap (2.16 eV) changes to the spin gaps of 1.53 and 1.65 eV. This monolayer is a III-V ferromagnetic, that it can be used in the spin field effect transistors (FET). We showed that the adsorption of (CH3)2Hg by g-GaN + Te monolayer is possible. The g-GaN + Te+(CH3)2Hg layer is n-type, and its band gap is 2.23 eV. Both g-GaN + Te and g-GaN + Te+(CH3)2Hg layers, beside the g-GaN monolayer, can be used in the GaN-based p-n junction betavoltaic cells and GaN p-i-n diodes. Also, in the g-GaN + Te+(CH3)2Hg case there are two terahertz gaps with values of 0.02 and 0.11 eV. After calculating the optical properties of both g-GaN + Te and g-GaN + Te+(CH3)2Hg layers by TDDFT, we found that the refractive index has values of 1.15 and 1.25, respectively. Also, the g-GaN + Te and g-GaN + Te+(CH3)2Hg layers, each have one visible absorption peak at 2.89 and 1.83 eV, respectively.