The recent research results on molecular beam epitaxy of HgCdTe on CdZnTe were presented. The CdZnTe substrates mounting process, under protective atmosphere, was essential to avoid substrate oxidation. It was demonstrated by in-situ reflection high-energy electron diffraction (RHEED), during deoxide process. Concerning the poor thermal conductivity of CdZnTe, good uniformity of HgCdTe on CdZnTe is hard to obtained, compared with the epitaxy on GaAs or Si. It was found that the crystal quality of HgCdTe/CdZnTe was strongly temperature dependent. According to good morphology, crystal quality and maintenance efficiency, the proper growth temperature range of HgCdTe/CdZnTe is 191~193°C. By the enhanced thermal contact sticking during substrate mounting, the uniformity of HgCdTe on CdZnTe was improved, including Cd composition, morphology, as well as crystal quality. In addition, proper in-suit high temperature anneal can reduce dislocation density of HgCdTe epilayers about half order of magnitude. High quality uniform HgCdTe epilayers on 30mm×30mm CdZnTe Substrates were obtained under the optimized growth condition. The X-ray double-crystal rocking curve (XDRC) full-width at half-maximum (FWHM) values vary in a range of 20~30 arcsec. EPD values are bellow 2×10<sup>5</sup> cm<sup>-2</sup>, with the best result of 3×10<sup>4</sup> cm<sup>-2</sup>.
The strain and stress distribution in HgCdTe/CdTe/Si heterostructure (Si 500<i>μm</i>, CdTe 10<i>μm</i>, HgCdTe 10<i>μm</i>) were described by theoretical calculation. The results showed that the strain and stress profiles and curvature radius of HgCdTe/CdTe/Si oriented in asymmetry  direction, are asymmetric along in-plane direction along [1-1-1] and [01-1]. The strain of epilayer and substrate are both negative at 77K. The stress at the interface is the largest in this heterostructure. The stress in epilayer is tensile while in substrate it is compressive on the side of interface and tensile on the other side. And a quantitative reference of the Si substrate thickness for a hybrid infrared focal plane arrays was provided.
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<sup>+</sup>. 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.