Modeling of disorder in II-IV-V₂ semiconductors for tuning of novel properties

The customization of multinary semiconductors has attracted great interest in the science community for a diverse set of novel applications. The properties of these materials can be fine-tuned by controlling composition and atomic ordering. However, an understanding of the structure-synthesis-property relationship is essential for a rational design. In this contribution, we use two II-IV-V₂ materials: ZnSnN₂ and ZnGeN₂ as examples to illustrate the ordering effects. Model Hamiltonian based Monte Carlo simulations were used to create structures with different degrees of disorder. The energies and electronic structures were estimated from first principles calculations. We find that energies of ZnSnN₂ can be well approximated by a Motif Hamiltonian which incorporates only short-range ordering. We demonstrate that, only with the consideration of disorder and oxygen contamination, the net doping level in ZnSnN₂ can be lowered to agree with experiments (10¹⁷ cm^-3). However, for ZnGeN₂, long-range ordering effects step in, and thus, we use the Cluster Expansion Hamiltonian to create disordered structures. The thermodynamics and optoelectronic properties of disordered ZnGeN₂ will be discussed.