Effects of deep-level defects on carrier mobility in CdZnTe crystals

The effects of deep-level defects on the carrier mobility of Cd_0.9Zn_0.1Te:In single crystals were studied. The total density of donor and acceptor defects in two samples, CZT1 and CZT2, was measured by the thermally stimulated current (TSC) to be ~2.0×10¹⁶ cm^-3 and ~3.8×10¹⁷ cm^-3, respectively. The mobility of electrons was measured by time-of-flight (TOF) technique to be 848±42 cm²/Vs in CZT1 and 337±17 cm²/Vs in CZT2. Theoretical estimation of the mobility was made considering the contributions from a variety of scattering mechanisms, including polar-optical phonon scattering, piezoelectric potential scattering, deformation potential scattering and ionized impurity scattering. The total electron mobility was estimated based on Matthiesens rule to be 1004 cm²/Vs in CZT1 and 352 cm²/Vs in CZT2, according to the defect density. Polar-optical phonon scattering was found to be the dominant scattering mechanism limiting the mobility at room temperature when the total defect density is lower than 1.0×10¹⁵ cm^-3, and ionized impurity scattering will be the dominant when the total defect density higher than 1.0×10¹⁷ cm^-3.