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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]

InAs/GaSb mid-wave, cascaded superlattice light emitting diodes are found to give higher radiance when epitaxially grown on mismatched GaAs substrates compared to lattice-matched GaSb substrates. Peak radiances of 0.69 W/cm2-sr and 1.06 W/cm2-sr for the 100×100 µm2 GaSb and GaAs-based devices, respectively, were measured at 77 K. Measurement of the recombination coefficients shows the shorter Shockley-Read-Hall recombination lifetime as misfit dislocations for growth on GaAs degrade the quantum efficiency only at low current injection. The improved performance on GaAs was found to be due to the higher transparency and improved thermal properties of the GaAs substrate. [ABSTRACT FROM AUTHOR]

Temperature-dependent measurements of carrier recombination rates using a time-resolved optical pump-probe technique are reported for mid-wave infrared InAs/InAs1–xSbx type-2 superlattices (T2SLs). By engineering the layer widths and alloy compositions, a 16K band-gap of ~235±10 meV was achieved for five unintentionally and four intentionally doped T2SLs. Carrier lifetimes were determined by fitting lifetime models based on Shockley-Read-Hall (SRH), radiative, and Auger recombination processes to the temperature and excess carrier density dependent data. The minority carrier (MC), radiative, and Auger lifetimes were observed to generally increase with increasing antimony content and decreasing layer thickness for the unintentionally doped T2SLs. The MC lifetime is limited by SRH processes at temperatures below 200K in the unintentionally doped T2SLs. The extracted SRH defect energy levels were found to be near mid-bandgap. Also, it is observed that the MC lifetime is limited by Auger recombination in the intentionally doped T2SLs with doping levels greater than n~1016 cm–3. [ABSTRACT FROM AUTHOR]

The impact of post growth annealing on the electrical properties of a long wavelength infrared type-II superlattice (SL) was explored. Quarters of a single SL wafer were annealed at 440 °C, 480 °C, and 515 °C, respectively for 30 min. Changes in the electrical properties were followed using spectral photoconductivity, temperature dependent Hall effect, and time-resolved pump-probe measurements. The bandgap energy remained at ∼107 meV for each anneal, and the photoresponse spectra showed a 25% improvement. The carrier lifetime increased from 12 to ∼15 ns with annealing. The electron mobility was nearly constant for the 440 °C and 480 °C anneals, and increased from ∼4500 to 6300 cm2/Vs for the 515 °C anneal. [ABSTRACT FROM AUTHOR]

We report studies of the effect of rapid thermal annealing (RTA) on the optical properties of a low-loss 1.3 μm saturable Bragg reflector (SBR), consisting of a GaInNAs/GaAs single quantum well embedded in an AlAs/GaAs Bragg reflector grown monolithically on a GaAs substrate. RTA gives rise to a blueshift of the photoluminescence (PL) peak (and therefore of the excitonic absorption peak) and an enhancement of PL intensity, while the reflectivity properties including peak reflectivity and bandwidth are not degraded. Temperature dependent photoluminescence measurements show that the RTA-induced blueshift of photoluminescence consists of two components: one originating from the increase of optical transition energies and another from the reduction of carrier localization. Time-resolved photoluminescence results at room temperature provide information about the recombination dynamics of carriers directly relevant to the application of the SBR in laser mode locking. [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]

Cascaded superlattice LEDs were designed, grown, fabricated, and tested with an n-type anode structure consisting of a variably doped n-GaSb buffer layer and a variable tunnel junction of n-GaxIn1-xAsySb1-y/p-GaSb in place of a conventional p-doped anode contact layer. The elimination of p-doped contact layers from the structure was found to reduce parasitic optical absorption and ohmic loss. After selecting the ideal design from the 4 stage test structures, a nominally identical 16 stage n-type anode structure was grown, yielding an MWIR radiance of 6.7W/cm2/sr. [ABSTRACT FROM AUTHOR]

Measurements of carrier recombination rates using a time-resolved pump-probe technique are reported for mid-wave infrared InAs/InAs1-xSbx type-2 superlattices (T2SLs). By engineering the layer widths and alloy compositions, a 16K band-gap of ~235¯10meV was achieved for all five unintentionally doped T2SLs. Carrier lifetimes were determined by fitting a rate equation model to the density dependent data. Minority carrier lifetimes as long as 10 µs were measured. On the other hand, the Auger rates for all the InAs/InAsSb T2SLs were significantly larger than those previously measured for InAs/GaSb T2SLs. The minority carrier and Auger lifetimes were observed to generally increase with increasing antimony content and decreasing layer thickness. [ABSTRACT FROM AUTHOR]

Minority carrier lifetimes in doped and undoped mid-wave infrared InAs/InAsSb type-II superlattices (T2SLs) and InAsSb alloys were measured from 77-300 K. The lifetimes were analyzed using Shockley-Read-Hall (SRH), radiative, and Auger recombination, allowing the contributions of the various recombination mechanisms to be distinguished and the dominant mechanisms identified. For the T2SLs, SRH recombination is the dominant mechanism. Defect levels with energies of 130 meV and 70 meV are determined for the undoped and doped T2SLs, respectively. The alloy lifetimes are limited by radiative and Auger recombination through the entire temperature range, with SRH not making a significant contribution. [ABSTRACT FROM AUTHOR]

Time-resolved differential transmission measurements were used to investigate vertical charge carrier transport in mid-wave infrared InAs/GaSb type-II superlattices (T2SLs). By optically generating excess carriers near one end of the mid-wave T2SL and measuring the transit time to a thin, lower-bandgap T2SL at the other end, the time-of-flight of vertically diffusing carriers was measured. Through investigation of both unintentionally doped and p-type T2SLs, the vertical hole and electron diffusion coefficients were measured to be 0.04 ± 0.03 cm2/s and 4.7 ± 0.5 cm2/s, corresponding to vertical mobilities of 6 ± 5 cm2/Vs and 700 ± 80 cm2/Vs, respectively, at a temperature of 77 K. [ABSTRACT FROM AUTHOR]

Measurements of carrier recombination rates using time-resolved differential transmission are reported for an unintentionally doped mid-wave infrared InAsSb alloy and InAs/InAsSb superlattice. Measurements at 77 K yield minority carrier lifetimes of 3 μs and 9 μs for the InAsSb alloy and InAs/InAsSb superlattice, respectively. The un-optimized InAsSb-based materials also exhibit long lifetimes (>850 ns) at temperatures up to 250 K, indicating the potential use for these materials as mid-wave infrared photodetectors with improved performance over current type-II superlattice photodetectors at both cryogenic and near-ambient operating temperatures. [ABSTRACT FROM AUTHOR]

Tunnel junctions in cascaded structures must provide adequate barriers to prevent carriers from leaking from one emission region to the next without first recombining radiatively, while at the same time remain low in tunneling resistance for current recycling. In this study, a variety of tunnel junction designs are compared in otherwise identical four stage InAs/GaSb superlattice light emitting diodes, which past studies have found hole confinement to be problematic. Here we used GaSb on the p-side of the junction, while varying materials on the n-side. The authors find Al0.20In0.80As0.73Sb0.27 tunnel junctions function best due to the low set of the conduction band; Ga0.75In0.25As0.23Sb0.77 also works well, though is more resistive due to a reduced set of the conduction band; and GaSb, while giving good hole confinement, results in a very resistive junction. Graded superlattice junctions can also work well, though they show sensitivity to doping levels, and present some challenges in growing strain-free. [ABSTRACT FROM AUTHOR]

We report on the growth and characterization of InAs/GaSb superlattice light emitting diodes (LEDs) operating in the midwave infrared at 3.8 μm at 77 K. Devices were grown by solid source molecular beam epitaxy on (100) GaSb substrates and were fabricated into 120×120 μm2 mesa devices using wet etching. By employing an eight-stage cascaded active region design, output powers in excess of 1.5 mW were achieved at 77 K with 100 mA peak drive current and a 50% duty cycle. Operating characteristics of the devices were examined from room temperature to 77 K under quasi-dc excitation conditions. [ABSTRACT FROM AUTHOR]

We report the demonstration of room temperature gate control over the electron spin dynamics using the Rashba effect in a (110) InAs/AlSb two-dimensional electron gas. Our calculations predict that the strong spin–orbit interaction in this system produces pseudomagnetic fields exceeding 1 T when only 140 mV is applied across a single quantum well. Using this large pseudomagnetic field, we demonstrate low-power spin manipulation on a picosecond time scale. Our findings are promising for the prospect of nonmagnetic low-power, high-speed spintronics. [ABSTRACT FROM AUTHOR]

Growth of high-quality Sb-based resonant tunneling diodes in the (110) orientation is demonstrated. The room-temperature current–voltage characteristics of the diodes are studied as a function of GaSb well width. Electronic band structure calculations including spin support the conclusion that the position of the GaSb light hole band with respect to the InAs conduction band is responsible for the strength of the negative differential resistance observed. The spin splitting of the heavy hole band is calculated to be larger than the light hole band suggesting that the observation of negative differential resistance may not be necessary or desirable for spin transport in these structures. [ABSTRACT FROM AUTHOR]