Cd-Te

Abstract: CdTe and Cd_1−xZn_xTe are the leading semiconductor compounds for both photovoltaic and radiation detection applications. The performance of these materials is sensitive to the presence of atomic-scale defects in the structures. To enable accurate studies of these defects using modern atomistic simulation technologies, we have developed a high-fidelity analytical bond-order potential for the CdTe system. This potential incorporates primary (σ) and secondary (π) bonding and the valence dependence of the heteroatom interactions. The functional forms of the potential are directly derived from quantum-mechanical tight-binding theory under the condition that the first two and first four levels of the expanded Green's function for the σ- and π-bond orders, respectively, are retained. The potential parameters are optimized using iteration cycles that include first-fitting properties of a variety of elemental and compound configurations (with coordination varying from 1 to 12) including small clusters, bulk lattices, defects, and surfaces, and then checking crystalline growth through vapor deposition simulations. It is demonstrated that this CdTe bond-order potential gives structural and property trends close to those seen in experiments and quantum-mechanical calculations and provides a good description of melting temperature, defect characteristics, and surface reconstructions of the CdTe compound. Most importantly, this potential captures the crystalline growth of the ground-state structures for Cd, Te, and CdTe phases in vapor deposition simulations.

Abstract: We study the liquid-vapor interface of CdTe by a Monte Carlo technique. The interatomic interactions are modeled by a combination of two-body and three-body potentials, using the form proposed by Stillinger and Weber, but with the parameters fitted to bulk atomization energies, lattice constants, and melting temperatures. The calculated heat of fusion and elastic constants agree well with experiments. The surface tension is calculated with a direct Monte Carlo evaluation of the free energy required to create the surface. The calculated surface tension is found to be about 220 ergs/cm², in good agreement with experimental estimates. The surface region is found to be Cd rich, even though elemental Cd has a higher surface tension than elemental Te.