Fabrication and Characterization of MOVPE-Grown CdTe-on-Si Heterojunction Diode-Type Gamma-Ray Detectors

• Published in: Journal of electronic materials 2008-09, Vol.37 (9), p.1391-1395
• Main Authors: Yokota, M., Yasuda, K., Niraula, M., Nakamura, K., Ohashi, H., Tanaka, R., Omura, M., Minoura, S., Shingu, I., Agata, Y.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cadmium telluride; Characterization and Evaluation of Materials; Chemistry and Materials Science; Cross-disciplinary physics: materials science; rheology; Diodes; Electronics; Electronics and Microelectronics; Exact sciences and technology; Gamma rays; Instrumentation; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Materials; Materials Science; Methods of deposition of films and coatings; film growth and epitaxy; Microelectronic fabrication (materials and surfaces technology); Optical and Electronic Materials; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon; Solid State Physics; Substrates; Vapor phase epitaxy; growth from vapor phase; X- and γ-ray instruments and techniques; X- and γ-ray sources, mirrors, gratings and detectors
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-008-0430-7

We report on the growth of very thick (>260  μ m) high-crystalline-quality single-crystal CdTe epitaxial films on (211) Si substrates in a metalorganic vapor-phase epitaxy reactor, and the development of gamma ray detectors and their radiation detection properties. Films were grown with a high growth rate varying from 40  μ m/h to 70  μ m/h. A heterojunction diode was fabricated by growing a 90- μ m-thick CdTe layer on an n + -Si substrate, which exhibited good rectifying behavior and had a low reverse bias leakage current of 0.18  μ A/cm 2 at 100 V bias. The diode clearly demonstrated its gamma radiation detection capability by resolving energy peaks from the 241 Am radioisotope during room-temperature measurements. By cooling the diode detector to −30°C, the leakage current could be reduced by three orders of magnitude from the room-temperature value. At this operating condition dramatic improvements in the pulse height spectrum were observed.