The structural evolution along the alloy between the ordered vacancy compound Hg₂GeTe₄and Cu₂HgGeTe₄ was quantified as this alloy space is correlated with major changes in the carrier concentration. The alloy shows strong local ordering despite four distinct cationic species (Cu, Ge, Hg, vacancies) at high concentration. Further, the results indicated that the Cu_Hg defects are driving the carrier concentration in the Cu_2xHg_2−xGeTe₄ alloy.

The transformation from Hg₂GeTe₄ to Cu₂HgGeTe₄ was studied through defect calculations and resonant X-ray diffraction; these efforts identified the presence of local ordering of defects along the alloy continuum and the impact of this local ordering on the carrier concentration and dopability.

The experimentally measured hole concentration is plotted here as a function of the Cu_Hg defect concentration from REXRD. The nearly 1:1 correlation indicates that Cu_Hg antisite defects are responsible for controlling the carrier concentration of Cu_2xHg_2−xGeTe₄ alloys.