  SnSe monolayer with orthorhombic Pnma GeS structure is an important
two-dimensional (2D) indirect band gap material at room temperature. Based on
first-principles density functional theory calculations, we present systematic
studies on the electronic and magnetic properties of X (X = Ga, In, As, Sb)
atoms doped SnSe monolayer. The calculated electronic structures show that
Ga-doped system maintains semiconducting property while In-doped SnSe monolayer
is half-metal. The As- and Sb- doped SnSe systems present the characteristics
of n-type semiconductor. Moreover, all considered substitutional doping cases
induce magnetic ground states with the magnetic moment of 1{\mu}B. In addition,
the calculated formation energies also show that four types of doped systems
are thermodynamic stable. These results provide a new route for the potential
applications of doped SnSe monolayer in 2D photoelectronic and magnetic
semiconductor devices.
