Transport and noise properties of CdTe(Cl) crystals

Experimental studies of transport and noise characteristics of CdTe (Cl doped) crystals, prepared by travelling heater method, have been carried out. The basic material is of p-type with p=1.8×10¹⁴ m⁻³, μ_h=0.0065 m² V⁻¹ s⁻¹, μ_e=0.13 m² V⁻¹ s⁻¹. The current and noise spectral density was measured as a function of the sample illumination, voltages across the sample and incident light wavelengths. Two types of effective charge carrier mobility are assumed: namely, the effective transport mobility, which is 0.065 m² V⁻¹ s⁻¹ and the effective noise mobility, which reaches a value of 0.125 m² V⁻¹ s⁻¹, both for high illumination. Under the same conditions, the density of light generated charge carrier pairs is 1.7×10¹⁵ m⁻³. Experimental results are in a good agreement with the four-level recombination model. The values of 1/f noise parameter α range from 4×10⁻⁴ to 2.5×10⁻³. The α parameter grows with almost the photocurrent square root. The signal-to-noise ratio improves if the electric field strength in the CdTe detector is set to a higher value.