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The internal quantum efficiency of a series of InAs/GaSb superlattices was investigated as a function of carrier generation rate through variable excitation, quasicontinuous-wave photoluminescence measurements. GaSb thicknesses were varied to maximize the internal quantum efficiency for midwave infrared emission. Internal quantum efficiencies were determined from measurements of the photoluminescence radiance and extraction efficiencies computed within a two-slab model. The peak internal quantum efficiencies varied from 15% to 29% at 77 K, which is in good agreement with expectations from InAs/GaSb superlattice light-emitting diode performance. [ABSTRACT FROM AUTHOR]

The paper presents a theoretical study of the modulation instability of a continuous or quasicontinuous optical probe in a three level quantum well system under electromagnetically induced transparency. The modulation instability is affected by the control field detuning, as well as even-order dispersion and by the strength of Kerr (third-order) and quintic (fifth-order) nonlinearities. The fourth-order dispersion reduces the bandwidth over which modulation instability occurs, whereas the quintic nonlinearity saturates the growth of the modulation instability. Detuning the control field from resonance can significantly reduce the growth of the modulation instability at both low and high power levels. At low powers, the system becomes stable against modulation instability for small detuning of the control field and at high powers modulation instability disappears for larger detuning. [ABSTRACT FROM AUTHOR]

We report on the growth, processing, and characterization of uncoated, unpassivated GaInAsSb detector mesa photodiodes with a cutoff wavelength of 2.4 μm. We find peak room temperature specific detectivity value of 6×1010 cm Hz1/2/W and maximum zero-bias resistivity of 25 Ω cm2. The zero-bias resistivities of mesas with areas ranging from 502 μm2 to 1 mm2 were found to be limited by generation-recombination currents at mesa sidewalls. At low temperatures, devices were limited by Ohmic leakage, which is likely due to the formation of oxides on the sidewalls. After 6 months of aging, Ohmic leakage becomes the limiting factor at room temperature as well. Based on experimentally obtained material parameters in this and other studies, an upper limit D* and R0A were estimated for GaInAsSb materials and compared to those HgCdTe and InGaAs. [ABSTRACT FROM AUTHOR]

A comparison is performed between measured and calculated Auger recombination rates for four different narrow-gap superlattices based on the InAs/GaSb/AlSb material system. The structures are designed for optical or electrical injection for mid-infrared laser applications, with wavelengths ranging from 3.4 to 4.1 µm. The electronic band structures are computed employing an accurate 14-band restricted basis set (superlattice K·p) methodology that utilizes experimental information about the low-energy electronic structure of the bulk constituents. The superlattice band structures and their associated matrix elements are directly employed to compute Auger recombination rates. Varying amounts of Auger recombination suppression are displayed by the various superlattices as compared to bulk mid-infrared systems. The greatest disagreement between theory and experiment is shown for the structure predicted to have the most Auger suppression, suggesting the suppression is sensitive either to theoretical or growth uncertainties. [ABSTRACT FROM AUTHOR]

Despite recent progress in electronic structure engineering of type-II materials for mid-infrared lasers, suppression of Auger recombination at room temperature has been limited. We present an active region design, consisting of AlAsSb/InAs/GaInSb/InAs/AlAsSb wells separated by an InAs/AlGaSb superlattice, that overcomes this limitation. The 300 K calculated Auger recombination rate in this structure at the optimal lasing density is five times smaller than typical Shockley-Read-Hall (defect-assisted) recombination rates. An integrated separate confinement heterostructure design suitable for this active region is also described. The separate confinement region, which is a lightly doped InAs/AlGaSb superlattice, provides efficient hole transport and injection into the active region. For an estimated nonactive region modal cavity loss of 20 cm-1 and an optical mode width of 1.3 μm, the calculated internal threshold current density is 100 A/cm2 at 300 K for a single quantum well device. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which calculated the linewidth enhancement factor for midinfrared active region quantum well materials. Optical properties of the materials; Strategies used for reducing the linewidth enhancement factor in near-infrared lasers; Conclusions.

Presents information on a study which described the differential gain, differential refractive index and linewidth enhancement factor in a type-II InAs/GaInSb-based superlattice intended for use in midwave-infrared semiconductor lasers. Details on the superlattice grown by molecular beam epitaxy; Experimental details; Results and discussion; Conclusions.

A temperature-insensitive method for measuring protein concentration in aqueous solutions using near-infrared spectroscopy is described. The method, which is based on identification of the net analyte signal of single-beam spectra, can be calibrated using a single protein absorbance measurement and is thus well suited for crystallization monitoring where the quantity of protein is limited. The method is applied to measurements of glucose-isomerase concentration in a sodium phosphate buffer that is actively varied over the temperature range of 4-24 [degrees] C. The standard error of prediction using the optimized spectral range of 4670-4595 [cm.sup.-1] is 0.12 mg/mL with no systematic trend in the residuals with solution temperature. The method is also applied to previously collected spectra of hen egg-white lysozyme and yields a standard error of prediction of 0.14 mg/mL. Spectra sampled at discrete wavelengths can also be used for calibration and prediction with performance comparable to that obtained with spectral bands. A set of four wavelengths are identified that can be used to predict concentrations of both proteins with a standard error less than 0.14 mg/mL.

By cascading multiple GaInAsSb active regions, the authors have fabricated 2.4 μm light-emitting diodes that, for a given light output, operate at reduced current and higher voltage, which can be advantageous for battery-powered sensor applications. Tunnel heterojunctions separating emission regions add no measurable series resistance. Devices are demonstrated at room temperature with continuous wave output. [ABSTRACT FROM AUTHOR]

Discusses the ideal performance of cascade and noncascade intersubband and interband long-wavelength semiconductor lasers. Challenges associated with the design of semiconductor laser diodes; Net material gain per unit volumetric power dissipation in the active region.