A roadblock in utilizing III-V semiconductors for scaled-down electronic devices is its poor dopant activation. As a first step to unravel the dopant behavior in InGaAs, we studied the tendency for dopant formation computationally using two approaches: ab initio and semiempirical methods. We studied a number of structural possibilities such as the impact of local sites, local and global environments, etc. We will show that the dopant we considered here, Si, has discrete preferences for certain sites and the nature of its surroundings. Substitutional defects are clearly preferred over interstitial locations. We shall show that cation ordering has an impact on dopant energetics. Critically, for large-scale simulations of dopant diffusion in InGaAs alloys, we also present a parameterization of the Abell-Tersoff semi-empirical potential for pairwise interactions between silicon atoms and each of the elements comprising InGaAs. In the absence of experimental data, reference parameters for estimating the Tersoff values were obtained using ab initio pseudopotential calculations (DFT+GGA). These sets of Tersoff parameters were optimized to describe the bulk structural properties of the mostly theoretical alloys, Si-As, Si-Ga and SI-In. We demonstrate the transferability of these parameters by predicting formation energies of extrinsic point "defects" of Si on a variety of sites in ternary InGaAs alloys with different local compositional configurations, both random and ordered. Tersoff model predictions of the extrinsic "substitution energy" of a Si dopant on a cationic lattice site were found to be independent of the composition of the dopant's 2 nd nearest neighbors, but was affected by the strain induced by a local arrangement of In and Ga cationic atoms. This finding is important since common deposition processes used to create InGaAs may lead to specifically ordered patterns within the cation sub-lattice.