Energetics of neutral Si dopants in InGaAs: Anab initioand semiempirical Tersoff model study

Abstract

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.

Thermal expansion of III–V materials in atomistic models using empirical Tersoff potentials

“…These potentials were also proven to be reliable regarding the elastic behaviour or bond length distributions in binary compounds as well as random and spontaneously ordered ternary structures [9][10][11][12]. Such models were recently also extended to describe the behaviour of dopant atoms in III-V materials [13].…”

N-type Doping Strategies for InGaAs

“…Other recent DFT studies have been carried out to calculate the energetics of the possible diffusion mechanisms and defects in InGaAs [98,99]. Their work supports the trend that formation energies of cation vacancies V In V Ga , decreases with increasing Fermi level and that the formation energy of interstitial Si is much higher than that of substitutional silicon.…”

Ab Initio Studies of the Diffusion of Intrinsic Defects and Silicon Dopants in Bulk InAs

“…In the As-rich regime, the chemical potential of As is assumed to be its chemical potential in bulk As, whereas in the In-rich (As-poor) regime, it corresponds to the chemical potential difference between InAs and bulk In (and vice versa for the chemical potential of In). For an in-depth discussion of formation energy calculations, the reader is referred to the following papers. ,− …”