Dilute nitrogen alloys of InSb exhibit strong band gap bowing with increasing nitrogen composition, shifting the absorption edge to longer wavelengths. The conduction band dispersion also has an enhanced nonparabolicity, which suppresses Auger recombination. We have measured Auger lifetimes in alloys with 11 and 15 m absorption edges using a time-resolved pump-probe technique. We find the lifetimes to be longer at room temperature than equivalent band gap Hg 1Ϫy Cd y Te alloys at the same quasi-Fermi level separation. The results are explained using a modified k"p Hamiltonian which explicitly includes interactions between the conduction band and a higher lying nitrogen-related resonant band. © 2001 American Institute of Physics. ͓DOI: 10.1063/1.1355301͔When a small fraction of anion atoms are replaced by nitrogen in GaInAlAs the band gap initially decreases rapidly, by between 0.05 and 0.2 eV at 1% N. [1][2][3][4] This opens the possibility of long wavelength applications in dilute nitride alloys. Despite the decrease in band gap, the conduction band ͑cb͒ edge effective mass has been observed to rise with increasing N content, 5,6 contrary to the prediction of usual k"p theory. The strong band gap bowing and increase in effective mass arise because of a repulsive interaction between the conduction band edge and a higher lying band of nitrogen resonant states. [7][8][9] The band structure of InN x Sb 1Ϫx can be predicted using a modified k"p Hamiltonian previously developed for GaN x As 1Ϫx . 7,8 In this model, the Hamiltonian describing the interaction between the cb edge and nitrogen resonant level is given by ͑1͒The parameters ␣, ␤, ␥, and the energy of the nitrogen resonant level, E N , can be found by analyzing the results of a tight binding model we have developed. 9 In the case of InN x Sb 1Ϫx , the cb energy E C ϭ0.177 eV (ϵ7 m), and we calculate E N ϭ0.647 eV, ␣ϭ␥ϭ0.77 eV, and ␤ϭ2.2 eV. The band gap is therefore predicted to decrease to 110 meV at 1% N, a fractional change of almost 40%. This clearly offers significant potential for long wavelength emission. III-V materials may be made with band gaps smaller than hitherto possible, opening up a longer wavelength region for direct interband transitions.Auger recombination ͑see Fig. 1͒ is the main recombination scattering process in intrinsic and n-type Kane band structure materials with band gap less than about 1 eV and, hence, is the primary factor limiting the maximum operating temperature of emitter and detector devices in this energy range. The Auger lifetime varies as

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A novel mid‐infrared transmission imaging (MIR‐TI) technique for the nondestructive, optical inspection of yttria‐stabilized tetragonal zirconia polycrystal (Y–TZP) components is described. This technique was designed specifically for the detection of flaws and cracks within the bulk of the ceramic component. The MIR‐TI technique exploits a transparency window in Y–TZP from 3 to 7 μm; at shorter wavelengths the material is highly scattering, while at longer wavelengths it is absorbing. We demonstrate that using this technique it is possible to detect micrometer‐scale flaws at depths of up to 6 mm.

We report the application of optically immersed, room-temperature InSb/InAlSb LED and photodiode devices to the ppm-level detection of nitrogen dioxide (NO2) at a wavelength of 6 µm. The LED emission and the photodiode detectivity are both increased by the optical immersion, resulting in a power dissipation of only 0.25 mW in the LED. A White cell is used for high gas sensitivity and its relatively small numerical aperture can be conveniently matched to the field of view of the hyperspherically immersed devices.