Passivation and surface effects in long-wavelength infrared HgCdTe photoconductors

Charles A. Musca; John F. Siliquini; Brett D. Nener; Lorenzo Faraone

doi:10.1117/12.218214

8 September 1995 Passivation and surface effects in long-wavelength infrared HgCdTe photoconductors

Charles A. Musca, John F. Siliquini, Brett D. Nener, Lorenzo Faraone

Proceedings Volume 2552, Infrared Technology XXI; (1995) https://doi.org/10.1117/12.218214
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

The performance enhancement that can be achieved by using wider bandgap Hg_1-xCd_xTe as a capping layer for long wavelength infrared Hg_1-xCd_xTe photoconductors has been studied using both theoretical and experimental results. In the theoretical section it is shown that in the presence of a suitable energy barrier between the Hg_1-xCd_xTe infrared absorbing layer and the overlaying passivation layer, the high surface recombination rate which is usually present at the semiconductor/passivant interface does not have a significant effect on device performance. The energy barrier, which repels photogenerated minority carries from the semiconductor surface, is introduced by employing a Hg_1-xCd_xTe wafer which consists of a wider bandgap layer grown on a long wavelength infrared absorbing layer. A device model is presented which allows the responsivity to be calculated by taking into account surface recombination at both the front and back interfaces, thickness of capping and absorbing layers, recombination at the heterointerface, and variations in equilibrium carrier concentration. Experimental results are presented for x equals 0.22 n-type Hg_1-xCd_xTe conventional single layer photoconductors, and for heterostructure photoconductors consisting of an absorbing layer of x equals 0.22 capped by an n-type layer of x equals 0.31. Using the derived model, a heterointerface recombination velocity of 250 cm/s is extracted for the two layer photoconductor. Experimental results indicate that photoconductors which include a wider bandgap capping layer give a responsivity improvement of more than five times that of a conventional single layer device. Furthermore, heterostructure photoconductors are shown to be insensitive to the condition of the semiconductor/passivant interface.

Citation Download Citation

Charles A. Musca, John F. Siliquini, Brett D. Nener, and Lorenzo Faraone "Passivation and surface effects in long-wavelength infrared HgCdTe photoconductors", Proc. SPIE 2552, Infrared Technology XXI, (8 September 1995); https://doi.org/10.1117/12.218214

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