Surface defects of molecular beam epitaxially grown HgCdTe are the major concern in developing large format
infrared focal plane arrays. Voids were usually observed on the HgCdTe surfaces as previously reported, they were
originated either from the improper substrates preparation or from the growth condition. However, the defects formation
with impurities has not been addressed. This paper presents our recent observation on defects induced by the impurities
involved in the mercury beam fluxes. These defects can be craters or bumps, having a spatially clustering feature. To
identify the origin of these kinds of defects, experiments were performed on HgCdTe as well as CdTe with mercury flux,
and the defects were observed and analyzed by using SEM and EDAX. The result, for the first time, confirmed that
impurities in the mercury beam were responsible to the formation of surface defects.
Dual color detection is a major concept of the third generation infrared focal plane arrays sensors (FPAs) for increasing
the demand of target identification. The performance of these detectors are largely relied on the growth capability of
HgCdTe multilayered structure. This paper presents our preliminary results on growth of MW/LW two-color structure by
using molecular beam epitaxy. The detector had NPpn architecture, with indium doped n-type bottom (window) layer
and Hg-vacancy doped MW and LW p-type layers. The top n-type layer was ion implanted by using B+. The
compositions (mole fraction x) of each layers and its gradient at the interfaces were measured by infrared transmission,
SIMS and SEM. The In doping layer was analyzed by SIMS. The electrical properties of In doping layer were measured
by Hall effects measurements. It was found that the structure obtained agreed well with the growth design. MW/LW two
color detectors of a 64×64 format were fabricated by mesa delineation, and the optimum structure was also discussed.
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