Surface structure of (111)A HgCdTe

The surface of (111)A HgCdTe has been studied by reflection high-energy electron diffraction and atomic force microscopy (AFM). The as-grown liquid-phase epitaxy (LPE) surface has bilayer (3.7 ± 0.2 A) step/terrace structures, macro-steps, and cross-hatch patterns. Macro-steps occur about the \([11\bar 2]\) and are from 10–40 A in height. AFM and x-ray measurements indicate the as-grown epilayer is ≈0.2° off-cut (random polar angle) from the (111). 〈110〉 cross-hatch lines consistent with bilayer (step height=3.9 ± 0.2 A) {111} slip dislocation are observed. The native oxide/carbon layer for the as-grown LPE (111)A HgCdTe is ≈8 A. The experimental results suggest that the as-grown LPE surface approximates an equilibrium vicinal crystal structure. The 0.1% Br:ethylene glycol wet chemically etched surfaces retained the macro-step structure, but numerous small protrusions (10–100 A height, ≈300 A diameter) developed. The plasma-etched (111)A HgCdTe surface is crystalline, but exhibits surface disorder and is roughened.