Abstract
Developing practical approaches to effectively reduce the amount of deep defect levels in semiconductors
is critical for their use in electronic and optoelectronic devices, but this still remains a very
challenging task. In this Letter, we propose that specific alloying can provide an effective means
to suppress the deep defect levels in semiconductors while maintaining their basic electronic properties.
Specifically, we demonstrate that for 2D transition-metal dichalcogenides, such as MoSe2
and WSe2, where anion vacancies are the most abundant defects that can induce deep levels, the
deep levels can be effectively suppressed in Mo1−xWxSe2 alloys at low W concentrations. This
surprising phenomenon is associated with the fact that the band edge energies can be substantially
tuned by the global alloy concentration, whereas the defect level is controlled locally by the preferred
locations of Se vacancies around W atoms. Our findings illustrate a new concept of alloy
engineering and provide a promising approach to control the defect properties of semiconductors.
