Dark Current Characteristics of a Radiation Detector Array Developed Using MOVPE-Grown Thick CdTe Layers on Si Substrate

• Published in: Journal of electronic materials 2012-10, Vol.41 (10), p.2754-2758
• Main Authors: Yasuda, K., Niraula, M., Fujimura, N., Tachi, T., Inuzuka, H., Namba, S., Muramatsu, S., Kondo, T., Agata, Y.
• Format: Article
• Language: English
• Subjects: Applied sciences; Arrays; Cadmium; Cadmium telluride; Cadmium tellurides; Characterization and Evaluation of Materials; Chemistry and Materials Science; Cross-disciplinary physics: materials science; rheology; Dark current; Detectors; Electronics; Electronics and Microelectronics; Exact sciences and technology; Gamma rays; Instrumentation; Materials; Materials Science; Methods of deposition of films and coatings; film growth and epitaxy; Molecular beam epitaxy; Nuclear radiation; Optical and Electronic Materials; Physics; Pixels; Silicon substrates; Solid State Physics; Substrates; Vapor phase epitaxy; growth from vapor phase
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-012-2121-7

We present reverse bias current (dark current) characteristics of a two-dimensional monolithic pixel-type nuclear radiation detector array fabricated using metalorganic vapor-phase epitaxy (MOVPE)-grown thick CdTe epitaxial layers on Si substrate. The (14 × 8) pixel array was formed by cutting deep vertical trenches using a dicing saw, where each pixel possesses a p -CdTe/ n -CdTe/ n + -Si heterojunction diode structure. The dark currents showed pixel-to-pixel variations when measured at higher applied biases exceeding 100 V. The dark current had a dependence on the pixel thickness, where pixels with lower CdTe thickness exhibited higher currents. Moreover, the temperature dependence of the dark current revealed that a deep level with activation energy of around 0.6 eV is responsible for the observed dark currents and their pixel-to-pixel variation. We discuss that the effective ratio of Te to Cd at the growth surface is a major factor that controls the thickness variation, and is also responsible for the formation of 0.6 eV deep levels.