Search

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]