  To reveal the infrared absorption causes in the wavelength region between
electronic and lattice absorptions, we measured the temperature dependence of
the absorption coefficient of $p$-type low-resistivity ($\sim 10^2~{\rm \Omega
cm}$) CdZnTe crystals. We measured the absorption coefficients of CdZnTe
crystals in four-wavelength bands ($\lambda=6.45$, 10.6, 11.6, 15.1$~\mu$m)
over the temperature range of $T=8.6-300$ K with an originally developed
system. The CdZnTe absorption coefficient was measured to be $\alpha=0.3-0.5$
${\rm cm^{-1}}$ at $T=300$ K and $\alpha=0.4-0.9$ ${\rm cm^{-1}}$ at $T=8.6$ K
in the investigated wavelength range. With an absorption model based on
transitions of free holes and holes trapped at an acceptor level, we conclude
that the absorption due to free holes at $T=150-300$ K and that due to
trapped-holes at $T<50$ K are dominant absorption causes in CdZnTe. We also
discuss a method to predict the CdZnTe absorption coefficient at cryogenic
temperature based on the room-temperature resistivity.
