Complex Behavior of Time Response of HgCdTe HOT Photodetectors

• Published in: Journal of electronic materials Vol. 44; no. 9; pp. 3163 - 3173
• Main Authors: Pawluczyk, J., Piotrowski, J., Pusz, W., Koźniewski, A., Orman, Z., Gawron, W., Piotrowski, A.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.09.2015; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Electronics and Microelectronics; High temperature; Instrumentation; Materials Science; Mercury cadmium telluride detectors; Optical and Electronic Materials; Solid State Physics; HgCdTe; photodiode; room temperature; heterostructure; time response; LWIR
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-015-3858-6

We report on the time response of higher-operating-temperature (HOT, T ∼200 K to 300 K) fast long-cutoff-wavelength infrared (LWIR) HgCdTe photodetectors. For a long time, photoconductive and photoelectromagnetic devices operating near room temperature have been used as fast (sub-nanosecond) photodetectors. Unfortunately, such devices suffer from relatively low detectivity. Recent efforts have focused on heterojunction photodiodes that offer both fast response and high performance. This paper presents computer simulations and experimental studies that reveal mechanisms limiting the time response and design rules to achieve short response time of HOT LWIR photodiodes operating at both zero and reverse bias. Complex time response curves with fast and slow components have been observed. The latter has been found to be mainly determined by the ambipolar diffusion of photogenerated charge carriers and by the diffusion capacitance combined with the built-in or external series resistance. The limitations are especially pronounced in zero-biased photodiodes characterized by large diffusion capacitance, where series resistance of only 1 Ω significantly reduces the response speed of devices with 100  μ m × 100  μ m photosensitive area.