Alloy Disorder and Partial Order Effects on the Bowing Parameter and Resistivity of CdZnTe Semiconductors

Cd1–xZnxTe (CZT) is an important semiconductor for applications in radiation detectors. As different concentrations of Zn, x, is alloyed into the CdTe crystal, the band gap of CZT varies with x, which can be described by a bowing parameter b that is independent of x. For CZT alloys, however, the measured b appears to have a full range of values, from very small to near unity, across CZT samples fabricated by different methods, experimental conditions, and labs. Such a large variation most likely reflects the microscopic details of the CZT atomic structures. In this work, we theoretically investigated atomic arrangements in the CZT on the bowing parameter by first principles modeling and found that the large variation in the bowing parameter may arise from uneven atomic distributions in partially ordered configurations. Such configurations represent intermediate states between fully disordered and fully ordered alloy structures. In particular, the completely randomized Zn distribution gives rise to small bowing parameters, and the partially ordered structures tend to produce much higher bowing. By comparing ZnTe/CdTe interface models with completely disordered models, this work provides valuable insights into the relationship between atomic arrangements, atomic-scale inhomogeneity, and the electronic properties of CZT. Finally, the disorder-limited resistivities of the CZT alloy models are calculated and compared.