Accurate determination of composition profiles in abrupt MBE-grown HgCdTe heterostructures

Richard H. Sewell; John M. Dell; Charles A. Musca; Lorenzo Faraone

doi:10.1117/12.522840

30 March 2004 Accurate determination of composition profiles in abrupt MBE-grown HgCdTe heterostructures

Richard H. Sewell, John M. Dell, Charles A. Musca, Lorenzo Faraone

Proceedings Volume 5274, Microelectronics: Design, Technology, and Packaging; (2004) https://doi.org/10.1117/12.522840
Event: Microelectronics, MEMS, and Nanotechnology, 2003, Perth, Australia

Abstract

Heterostructured Hg_(1-x)Cd_(x)Te photodetectors are important for the next generation of high performance Infra-Red (IR) sensing applications. The measurement of the composition and thickness of each layer in double layer HgCdTe heterostructures is examined in this paper, in particular, the use of infrared transmission and Secondary Ion Mass Spectroscopy techniques. Several authors have published models of the optical absorption coefficient and refractive index in HgCdTe, and these models have been assessed on their suitability for use in modelling the infrared transmission characteristics of multilayer HgCdTe films. No data is available for the refractive index of HgCdTe for photon energies around the bandgap energy, so a modified Sellmeier equation has been used to approximate the refractive index in this range. A versatile mathematical model of the infrared transmission of multilayer HgCdTe films is presented, based on the characteristic matrix of each layer. The model is then fit to experimental data, where the composition and thickness of each of the HgCdTe layers are fitting parameters. While some film parameters may be determined with high accuracy from infrared transmission, Secondary Ion Mass Spectroscopy (SIMS) is useful as a complimentary technique which enables the measurement of the composition of the wider bandgap HgCdTe layer in double layer HgCdTe films, as well as measurement of the interface abruptness and layer uniformity. A method of calibrating SIMS data is presented, which gives results consistent with those obtained from infrared transmission fitting. Room temperature infrared transmission spectra and SIMS depth profiles of HgCdTe layers grown by Molecular Beam Epitaxy at the University of Western Australia are presented, and are compared with theoretical composition vs. depth profiles which have been determined using elements of each measurement technique.

Citation Download Citation

Richard H. Sewell, John M. Dell, Charles A. Musca, and Lorenzo Faraone "Accurate determination of composition profiles in abrupt MBE-grown HgCdTe heterostructures", Proc. SPIE 5274, Microelectronics: Design, Technology, and Packaging, (30 March 2004); https://doi.org/10.1117/12.522840

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