In this research, we use the tight-binding model, which includes spin–orbit coupling and an external magnetic field, to describe the optical properties of the methyl-substituted germanane (GeCH3) monolayer. We have applied the Kubo formula, linear response theory, and Green's function approach to calculate the optical absorption coefficient of the GeCH3 monolayer. Here, the effects of an external magnetic field, strain, spin–orbit coupling, temperature, and electron/hole doping on the frequency dependence behavior of the optical conductivity have been investigated in detail. Our numerical results show that with increasing the external magnetic field, strain, and electron doping, the weight of the Drude increases. The optical absorption peak decreases and shifts to higher frequencies by applying an external magnetic field, strain, and electron doping. Controlling the optical and electronic properties of GeCH3 is leading to use this structure it in the electronic and optoelectronic industries.
