In this work, effective modulation of the electronic and magnetic properties of Janus \(\hbox {Si}_{{2}}\hbox {PAs}\) monolayer is proposed using vacancy engineering and doping with Ge atom. Pristine \(\hbox {Si}_{{2}}\hbox {PAs}\) monolayer is a non-magnetic indirect gap two-dimensional (2D) material with energy gap of 1.29(2.47) eV obtained from PBE(HSE06)-based calculations. The monolayer is metallized under effects of single Si1 (bound to P atom), Si2 (bound to As atom), P, and As vacancies, preserving its non-magnetic nature. Similar effects are induced by creating P+Si1 double vacancies. Meanwhile, the diluted magnetic semiconductor nature is induced by As+Si2 and Si1+Si2 pair vacancies with total magnetic moment of 0.98 and 1.81 \(\mu _{B}\) , respectively. Herein, magnetic properties are produced mainly by As and P atoms around defect sites. Interestingly, the indirect-to-direct gap transition is achieved by doping with Ge atom at Si1 and Si2 sites, and simultaneous doping at both Si1+Si2 sites, where the energy gap exhibits only slight change. In these cases, similar valence electronic configuration of Ge and Si atoms leads to the preservation of the non-magnetic nature. In contrast, the monolayer is significantly magnetized by doping at P and As sites, as well as simultaneous doping at P+Si1 sites. Such that a total magnetic moment of 1.00 \(\mu _{B}\) is obtained, which is generated mainly by Ge impurities. The spin-polarized band structures assert the diluted magnetic semiconductor nature of these doped \(\hbox {Si}_{{2}}\hbox {PAs}\) systems. Our results provide deep insights into the electronic properties of a new Janus \(\hbox {Si}_{{2}}\hbox {PAs}\) monolayer, and propose efficient approaches to make potential optoelectronic and spintronic candidates from this 2D material.
