Doping Effect Of B And Be In Hgcdte: First-principle Study

HgCdTe is an important material for infrared electronic detector. HgCdTe-based infrared detector can cover the whole infrared atmospheric window due to its band-gap can vary continuously in the range of 0 1.65 eV. However, along with the development of modern science and technology, the precision requirement for infrared detector is increasing. As a result, more and more problems are increasingly prominent in practical application of HgCdTe, especially the controllable doping in HgCdTe material. Such problems cannot only rely on the basis of empirical or semi-empirical theoretical framework. Based on first-principles method within the framework of the density functional theory, we study the effects of B and Be doping on the electronic properties of MCT material. Our results provide corresponding theoretical basis for controllable doping in experiments. The main results are as follows:(I) Using the formation energies and the binding energies, we study the doping effect of B in Hg_0.75Cd_0.25Te. We find that there are two major configurations for B impurity in Hg_0.75Cd_0.25Te. Firstly, B exists in hexagonal interstitial instead of substitutes one in perfect Hg_0.75Cd_0.25Te. B behaves as triple donors at this configuration, and the material is n-type. Secondly, B forms a complex impurity with Hg vacancy in Hg_0.75Cd_0.25Te with VHg native defect. The binding energy of the complex is up to 0.96eV. The complex is a single donor. Considering the formation of Hg vacancies because of the irradiation injury, the complex between the Hg vacancy and B is the main reason for the limitation of the activation of B implantation in Hg_0.75Cd_0.25Te.(II) Based on first-principles method within the framework of the density functional theory, we study the doping effect of Be in Hg_0.75Cd_0.25Te. By calculating the defect formation energy, we find that Be in situ substituting Hg mainly can easily form in Hg_0.75Cd_0.25Te, and Be behaves as a single donor. According to the analysis of the density of states, it is found that the Fermi level of Be doped Hg_0.75Cd_0.25Te locates in the conduction band, which indicates the Be impurity in MCT acts as a donor. The analysis of electron localization function shows that the Be impurity forms considerable strong polar covalent bond with near neighbor Te atom after Be in situ substituted Hg. Such strong covalent bond maintains the stable existence of the Be impurity in MCT.