Investigation of surface potential in the $V$-defect region of MBE Cd$_x$Hg$_{1-x}$Te film

Atomic-force microscopy is used to investigate the distribution of the contact-potential difference (surface potential) in Cd$_x$Hg$_{1-x}$Te epitaxial films grown by molecular-beam epitaxy. Modification of the solid-solution composition near the $V$-defect results in a variation in the contact-potential difference. It is shown that the solid-solution composition varies by $\sim$ 0.05 (2.5 at%) towards increasing mercury content in the $V$-defect region, and a region of mercury depletion by 0.36 at% is observed at the $V$-defect periphery. From analysis of the surface-potential distribution, it is shown that the Cd$_x$Hg$_{1-x}$Te epitaxial film contains unform $V$-defects with a diameter less than 1 $\mu$m in addition to macroscopic $V$-defects.