Study of surface passivation and contact deposition techniques in CdZnTe X-Ray and gamma-ray detectors

Abstract

Passivation and improved contact deposition techniques are known to reduce the surface leakage current and decrease noise levels of CdZnTe X-Ray and gamrna-ray detectors by improving their spectral energy resolutions. This paper presents a comparative study of surface passivation process in CdZnTe X-Ray and gamma-ray detectors. The experimental study compares three surface passivation processes: mechanically polished with a O.9μm Alumina Powder (AI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) finishing; mechanically polished with a O.9μm Alumina Powder (AI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) and etched with HBr + H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> solution for 2 minutes; mechanically polished with a O.9,.m Alumina Powder (AI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) and chemomechanically polished with bromine-methanol-ethylene glycol solution. The results show that chemo-mechanical polishing with bromine-methanol-ethylene glycol solution proved to be the best method out of the three for reducing surface leakage current. The preliminary results of aging studies on H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (Hydrogen Peroxide), NH4F (Ammonium Fluoride) + H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> + H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O and (NH4hS (Ammonium Sulfide) passivation agents are also presented.