Fabrication of Small-Pixel CdZnTe Sensors and Characterization with X-rays

• Main Authors: Stergios Tsigaridas, Silvia Zanettini, Manuele Bettelli, Nicola Sarzi Amadè, Davide Calestani, Cyril Ponchut, Andrea Zappettini
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Sensors
• Subjects: cadmium zinc telluride (CdZnTe); vertical Bridgman; high-Z sensors; pixel detectors; X-ray detectors; Timepix
• Online Access: https://www.mdpi.com/1424-8220/21/9/2932

Over the past few years, sensors made from high-Z compound semiconductors have attracted quite some attention for use in applications which require the direct detection of X-rays in the energy range 30–100 keV. One of the candidate materials with promising properties is cadmium zinc telluride (CdZnTe). In the context of this article, we have developed pixelated sensors from CdZnTe crystals grown by Boron oxide encapsulated vertical Bridgman technique. We demonstrate the successful fabrication of CdZnTe pixel sensors with a fine pitch of 55 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="normal">m</mi></semantics></math></inline-formula> and thickness of 1 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">m</mi></mrow></semantics></math></inline-formula> and 2 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="normal">m</mi><mi mathvariant="normal">m</mi></mrow></semantics></math></inline-formula>. The sensors were bonded on Timepix readout chips to evaluate their response to X-rays provided by conventional sources. Despite the issues related to single-chip fabrication procedure, reasonable uniformity was achieved along with low leakage current values at room temperature. In addition, the sensors show stable performance over time at moderate incoming fluxes, below <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>10</mn><mn>6</mn></msup></semantics></math></inline-formula> photons<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>.</mo><mi mathvariant="normal">m</mi><msup><mi mathvariant="normal">m</mi><mrow><mo>−</mo><mn>2</mn></mrow></msup><mo>.</mo><msup><mi mathvariant="normal">s</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula>.