Development of Large-Area CdTe/n+-Si Epitaxial Layer-Based Heterojunction Diode-Type Gamma-Ray Detector Arrays

• Published in: IEEE transactions on nuclear science 2018-04, Vol.65 (4), p.1066-1069
• Main Authors: Niraula, M., Yasuda, K., Kojima, M., Kitagawa, S., Tsubota, S., Yamaguchi, T., Ozawa, J., Agata, Y.
• Format: Article
• Language: English
• Subjects: Arrays; Cadmium compounds; CdTe; Crystals; Dark current; Detectors; Epitaxial growth; gamma detectors; Gamma ray detectors; Heterojunctions; II-VI semiconductor materials; Isotopes; large-area crystal; Metalorganic chemical vapor deposition; Pixels; response uniformity; Sensors; Silicon; Silicon substrates; Single crystals; Substrates
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2018.2812154

Growth of large area single crystal CdTe layers was studied on 25 \times 25 mm 2 (211) Si substrates using metalorganic vapor phase epitaxy. High crystalline quality thick crystals with very good material uniformity were obtained. A 2-D monolithic detector array comprising ( 20 \times 20 ) pixels was developed and evaluated. Each pixel is 1.12 \times 1.12 mm 2 size in a 1.17-mm pitch and consists of a p-CdTe/n-CdTe/n + -Si heterojunction diode structure, which is isolated from the surrounding pixels by making deep vertical cuts. The detector array exhibited highly uniform and low dark current, typically less than 0.5- \mu \text{A} /cm 2 per pixel at an applied reverse bias of 50 V. The spectroscopic performance was separately confirmed by dicing out a small portion from the array which clearly resolved energy peaks from 241 Am gamma isotopes at room temperature. On the other hand, a significant improvement in the detection property was observed by cooling it to −30 °C.