Hole mobility and Poole-Frenkel effect in CdTe

Abstract

We have performed, with the time‐of‐flight technique, an extensive investigation of the transport properties of holes in high‐resistivity CdTe as a function of temperature between 130 and 430 °K and for electric fields between 5 kV/cm and 50 kV/cm. In all investigated samples, at temperatures below 300 °K, the experimental hole mobility decreases on lowering either the temperature or the electric field. These features have been interpreted on the basis of the electric field effect on trapping and detrapping phenomena (Poole‐Frenkel effect) which cause a reduction of the mobility. A critical review of the existing theories of the Poole‐Frenkel effect is presented. The Poole‐Frenkel constant obtained by comparing the experimental data with the most reliable theories of the Poole‐Frenkel effect is in excellent agreement with its theoretical value. By analysis of the experimental data it was also possible to estimate the activation energy (E_t=0.14 eV) and the concentration (N_T=5×10¹⁶ cm⁻³) of the traps which caused the reduction of the mobility. These traps may be due to cadmium vacancies and the value of their concentration found here is in good agreement with previous estimates made in the same material.