Engineering the Bandgap of Unipolar HgCdTe-Based nBn Infrared Photodetectors

• Published in: Journal of electronic materials 2015-01, Vol.44 (1), p.158-166
• Main Authors: Kopytko, M., Wróbel, J., Jóźwikowski, K., Rogalski, A., Antoszewski, J., Akhavan, N. D., Umana-Membreno, G. A., Faraone, L., Becker, C. R.
• Format: Article
• Language: English
• Subjects: Band gap; Characterization and Evaluation of Materials; Chemistry and Materials Science; Electronics and Microelectronics; Engineering; Infrared imaging systems; Instrumentation; Materials Science; Numerical analysis; Optical and Electronic Materials; Optimization techniques; Solid State Physics
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-014-3511-9

Design of practically realizable unipolar HgCdTe nBn photodetectors has been studied in detail by numerical analysis. The simulations reported herein reveal that, by optimization of barrier doping, dark current levels can be reduced and collection efficiency substantially improved. It is shown that p -type doping of the barrier layer can significantly reduce the effective potential barrier arising from the valence band offset between the absorber and barrier regions, thus enabling HgCdTe nBn detector operation under near zero-bias conditions. However, relatively high electric fields in the space charge regions near the barrier/absorber interface result in enhanced trap-assisted Shockley–Read–Hall thermal generation. Our calculations indicate that nBn HgCdTe detectors with barriers engineered by use of HgTe/Hg 0.05 Cd 0.95 Te superlattices have, potentially, substantially better valence band alignment without the need for p -type doping.