Integration of semiconductor epitaxical nanostructures and nanocrystals into two classes of quantum structures, uncovered adsorbed nanocrystals or buried via epitaxical overgrowth, is successfully demonstrated through structural and optical studies. The combination InGaAs/GaAs epitaxical structures and InAs nanocrystals is employed as a vehicle with the functional aim of exploiting the well developed optoelectronic communication technology based on the former with the biochemical and biomedical applications for which the latter are well suited.
We report on the tailoring of detection bands of InAs quantum-dot infrared photodetectors ͑QDIPs͒ using In x Ga 1Ϫx As capping layers and on the realization of voltage-tunable two-color QDIPs for mid-wavelength infrared ͑MWIR͒ and long-wavelength infrared ͑LWIR͒ detection. QDIPs having 2.0 ML InAs QDs capped by 20 ML In 0.15 Ga 0.85 As layer show bias-dependent photocurrent peak positions in the LWIR regime (ϳ8 -9 m) which are redshifted with respect to those (ϳ5 -7 m) in the counterpart QDIPs without In x Ga 1Ϫx As capping layers. QDIPs having 2.5 ML InAs QDs capped by a 30 ML In 0.15 Ga 0.85 As layer have a bimodal QD size distribution and show voltage-tunable MWIR (ϳ5.5-6 m) and LWIR (ϳ9 -11 m) photoresponse. At low bias, MWIR photoresponse is dominant whereas with increasing bias, the LWIR photoresponse becomes dominant.
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