CdTe and CZT materials are technologies for gamma and x-ray imaging for applications in industry, homeland security,
defense, space, medical, and astrophysics. There remain challenges in uniformity over large detector areas (50~75 mm)
due to a combination of material purity, handling, growth process, grown in defects, doping/compensation, and metal
contacts/surface states. The influence of these various factors has yet to be explored at the large substrate level required
for devices with higher resolution both spatially and spectroscopically. In this study, we looked at how the crystal
growth processes affect the size and density distributions of microscopic Te inclusion defects. We were able to grow
single crystals as large as 75 mm in diameter and spatially characterize three-dimensional defects and map the
uniformity using IR microscopy. We report on the pattern of observed defects within wafers and its relation to
instabilities at the crystal growth interface.
InSb focal plane array (FPA) detectors are key components in IR imaging systems that significantly impact both cost and
performance. Detector performance is affected by the electronic and crystallographic quality and uniformity of the
semiconductor substrate. High-volume, high-yield production of InSb wafers to the standards required for FPA device
manufacture requires growth of on-axis {111} crystals. An inherent source of variation hindering on-axis Czochralski
crystal growth is anisotropic dopant incorporation. We report on newly developed growth methods that eliminate the
negative effects of anisotropic dopant incorporation enabling high volume manufacturing of {111}-oriented substrates
and discuss the consequential manufacturing benefits. We also report on a characterization technique to characterize
microscale dopant variation across the wafer.
We present a new method to produce low-cost, high quality gallium antimonide (GaSb) substrates for IR imaging
applications. These methods apply high-volume wafer manufacturing standards from the silicon industry to increase
performance and value of our wafers. Encapsulant-free GaSb single crystals were grown using the modified Czochralski
method, yielding more than seventy 150mm wafers per crystal or several hundred 75mm or 100mm wafers per crystal.
These were processed into epi-ready substrates on which superlattice structures were grown. Wafer and epitaxy structure
characterization is also presented, including transmission X-ray topography, dopant level and uniformity.
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