Preliminary results of large volume multi-pair coplanar grid CdZnTe detector fabrication

We present electrode fabrication techniques and preliminary test results of a multi-pair coplanar grid CdZnTe detector with a volume of 11 cm³, the largest single CdZnTe device ever fabricated. The crystal of initial dimensions 30.5×32.9×17.3 mm³ was grown by modified vertical Bridgman technique. The peculiarities of the growing process are analyzed. Crystal has high bulk resistivity of ρ = 1 × 10¹¹ ohm-cm, a value of (μτ)_e = 5.6×10^-3 cm²/V and a value of electron mobility μ_e = 675 cm²/Vs. Non-uniformity of material was found as result of crystal input test. Intergrid resistivity on all four segments of electrode structure was about 0.4 Gohm and 0.2 Gohm on Cd and Te side respectively. These values are significantly lower than that in our previous development. Dependences of resistivity on technological modes of passivation and on applied voltage are presented. Leakage current in all segments of detector did not exceed 10 nA at bias 1200 V. Spectra Cs-137 for all four segments of detector structure are presented.