Defects exhibiting trapping behaviors in semi-insulating (SI) materials were investigated by thermally stimulated current (TSC) spectroscopy. The variation of measurement conditions during the initial photoexcitation and thermal emission, such as the heating rate, bias voltage, illumination time and delay time, may bring some significant effects on TSC spectra, leading to incomplete characterization of trap levels. In this work, defects with deep levels in the band gap of SI-Cd0.9Zn0.1Te crystal, grown by the modified vertical Bridgman (MVB) method, were studied via TSC measurements. TSC measurement of the SI-CZT sample was performed with the optimized measurement conditions. Ten different traps and a deep donor (E-DD) level were characterized from the as-obtained spectrum in the temperature range from 25 to 310 K with the aid of simultaneous multiple peak analysis (SIMPA). The origins of these traps were identified in detail as well. (C) 2012 Elsevier B.V. All rights reserved.