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The type III band alignment of HgTe/CdTe superlattices leads to the interesting possibility of achieving very long wavelength infrared (VLWIR) (15 µm and longer) cutoff wavelengths with either normal (HgTe layer thickness less than about 70 Å for CdTe layer thickness of 50 Å) or inverted (HgTe thickness greater than about 70 Å) band structures. The inverted band structure superlattices promise even greater cutoff wavelength control than the normal band structure ones. However, the electronic band gaps of inverted band structure superlattices are substantially less than their optical band gaps, leading to large thermal carrier concentrations even at temperature as low as 40 K. These high carrier concentrations in turn give rise to more rapid Auger recombination than normal band structure superlattices with the same cutoff wavelengths. We conclude that the highest performance is expected from VLWIR HgTe/CdTe superlattice-based detectors with normal band structure absorber layers.

Photovoltaic p-n junctions are the most significant active components of both current infrared photodetectors and advanced ones being developed. It is of the utmost importance to control both p- and n-type extrinsic doping. This letter addresses the issue of activating arsenic as a p-type dopant of Hg1−xCdxTe at temperatures sufficiently low that the integrity of p-n junctions and the intrinsic advantages of molecular beam epitaxy as a growth technique will not be compromised. The p-type activation of arsenic in (211)B Hg1−xCdxTe is reported after a two-stage anneal at temperatures below 300 °C for Cd compositions suitable for the sensing of long wavelength infrared radiation.

Lead selenide (PbSe) nanowires were grown by magnetron sputtering on silicon with silicon dioxide (SiO2/Si) substrates, and characterized by scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, photoluminescence, and x-ray photoelectron spectroscopy. Closely packed PbSe nanowires of approximately 100 nm diameter grew in the ⟨111⟩ rock-salt cubic structure orientation. These large wires showed a large blueshift in the luminescence and absorption compared to the bulk crystal, demonstrating quantum confinement. This is attributed to a strong built-in field due to surface states, band bending, and a depletion layer which confines the carrier states.

In the natural photosynthesis process, light harvesting complexes (LHCs) absorb light and pass excitation energy to photosystem I (PSI) and photosystem II (PSII). In this study, we have used nanocrystalline quantum dots (NQDs) as an artificial LHC by integrating them with PSI to extend their spectral range. We have performed photoluminescence (PL) and ultrafast time-resolved absorption measurements to investigate this process. Our PL experiments showed that emission from the NQDs is quenched, and the fluorescence from PSI is enhanced. Transient absorption and bleaching results can be explained by fluorescence resonance energy transfer (FRET) from the NQDs to the PSI. This nonradiative energy transfer occurs in ∼6 ps. Current-voltage (I-V) measurements on the composite NQD-PSI samples demonstrate a clear photoresponse.