Charge collection properties of a CdTe Schottky diode for x- and γ-rays detectors

The electrical characteristics of x-ray and γ-ray detectors with Schottky diodes on the basis of CdTe crystals of n-type conductivity with a resistivity of 10²-10³ Ω cm (300 K) are investigated. The necessary parameters of the diode structures are determined to interpret the detection characteristics of the detectors. The dependences of the charge-collection efficiency in the detectors on the carrier lifetime and concentration of uncompensated donors are obtained and the conditions for the total collection of charges generated by the photon absorption are established. Taking into account drift and diffusion photocurrent components, the spectral distribution of the quantum detection efficiency is calculated. The comparative analysis of the detection efficiency of Schottky diodes based on low-resistivity p-CdTe and n-CdTe shows the advantages of the latter, especially in a low x-ray energy region.