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Two important classes of electro-optical devices, midwave-infrared interband cascade lasers (ICLs) and long-wave infrared photodiodes, employ type-II antimonide active regions grown by molecular beam epitaxy (MBE). The authors have studied how growth temperature and As flux affect the integrated intensity and linewidth of low-temperature photoluminescence spectra emitted from ICL active regions. Possible ramifications for defect-assisted Auger processes are discussed, and experimental Auger coefficients are extracted from the measured ICL thresholds and slope efficiencies. They also demonstrate that the effective dynamic impedance of a type-II photodiode with graded-gap depletion region is quite sensitive to the doping level in the absorber. Majority acceptor concentration is a key design parameter that must be carefully controlled in the MBE growth. [ABSTRACT FROM AUTHOR]

Negative luminescence (NL) refers to the suppression of infrared blackbody emission, and hence an apparent temperature reduction, due to free carrier extraction from a reverse-biased p-n junction. A number of applications are envisioned for NL devices, including cold shielding of background-limited uncooled and cryogenic focal-plane arrays, dynamic nonuniformity correction for ir imaging, and ir scene simulation. High-performance NL devices have recently been demonstrated. For example, a HgCdTe/CdZnTe photodiode with 4.8-µm cutoff wavelength achieved an internal NL efficiency of 95% at room temperature. This means that the blackbody emission was suppressed by a factor of 20 and that the apparent temperature of the device surface decreased by 60 K. The corresponding reverse-bias saturation current density was 0.11 A/cm². Even HgCdTe devices (λco = 5.3 µm) grown on large-area silicon substrates with substantial lattice mismatch displayed 88% internal NL efficiency and saturation current densities no larger than 1.3 A/cm². These results indicate a clear path toward a negative-luminescence device technology that is efficient, operates at low power, and is inexpensive. [ABSTRACT FROM AUTHOR]

Variable magnetic field Hall and transient photoconductance lifetime measurements were performed on a series of undoped, In-doped, and As-doped HgCdTe samples grown by molecular beam epitaxy and metalorganic chemical vapor deposition. Temperature variation and, in the case of Hall, magnetic-field variation are needed to give a more complete picture of the mechanisms that control lifetimes in HgCdTe samples. Recent predictions of recombination lifetimes from full band structure calculations were compared to experimental lifetimes at various doping levels at long-wave infrared (LWIR) and mid-wave infrared (MWIR) compositions. For n-type material, lifetimes from low doping levels fall well below the predictions, implying that Shockley-Read-Hall (SRH) recombination is still dominant. MWIR samples have a lifetime that increases somewhat with carrier concentration, suggesting that In doping passivates the SRH defects for that composition. Lifetimes in p-type MWIR material appear to be well-explained by recent theoretical calculations. In p-type material, trapping states may be introduced during the incorporation and activation of As, since some samples with unusually long lifetimes had a distinctly different type of temperature dependence. [ABSTRACT FROM AUTHOR]

Midinfrared broadband high-reflectivity Pb[sub 1-x]Sr[sub x]Se/BaF[sub 2] distributed Bragg reflectors and vertical-cavity surface-emitting lasers (VCSELs) with PbSe as the active material were grown by molecular-beam epitaxy. Because of an extremely high index contrast, mirrors with only three quarter-wave layer pairs had reflectivities exceeding 99%. For pulsed optical pumping, a lead salt VCSEL emitting at the cavity wavelength of 4.5-4.6 μm operated nearly to room temperature (289 K). © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report near-diffraction-limited output from an angled-grating distributed feedback type-II W laser emitting near 3.4 μm. For pulsed optical pumping of a 50-μm-wide stripe at 78 K, the far-field beam divergence angle was only 1.4°. The slope efficiency was 64% of that for a conventional Fabry-Pérot laser on the same bar. However, the spectral linewidth decreased by only a factor of 2. The beam quality was substantially better than that for the Fabry-Pérot laser out to stripe widths of at least 800 μm. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Mid-infrared (λ=3.25 μm) broadened-waveguide diode lasers with active regions consisting of 5 type-II "W" quantum wells operated in continuous-wave (cw) mode up to 195 K. At 78 K, the threshold current density was 63 A/cm[sup 2], and up to 140 mW of cw output power was generated. A second structure with ten quantum wells operated up to 310 K in pulsed mode. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Two different approaches, a photoconductive response technique and a correlation of lasing thresholds with theoretical threshold carrier concentrations have been used to determine Auger lifetimes in InAs/GaInSb quantum wells. For energy gaps corresponding to 3.1–4.8 μm, the room-temperature Auger coefficients for seven different samples are found to be nearly an order-of-magnitude lower than typical type-I results for the same wavelength. The data imply that at this temperature, the Auger rate is relatively insensitive to details of the band structure. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A 25-stage interband cascade laser with a W active region and a third hole quantum well for the suppression of leakage current has exhibited lasing in pulsed mode up to 286 K. A peak output power of 160 mW/facet and a slope efficiency of 197 mW/A per facet (1.1 photons per injected electron) were measured at 196 K. Above 200 K, the characteristic temperature was higher (T[sub 0]=53 K) and the threshold current densities lower than for a previously reported W interband cascade laser without the third hole quantum well. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Efficient (∼1%) second harmonic generation, resonantly enhanced near λ=8.6 μm, has been observed in asymmetric double multi-quantum well structures. We used (i) edge-emitting waveguide geometry where the phase matching was achieved by incorporating a separate multiple quantum well region which modifies (via the Kramers–Kronig relation) the dispersion of light and (ii) 45° wedge multi-bounce geometry where the phases of second harmonic waves generated at sequential bounces were synchronized by changing the angle of incidence. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Interband cascade (IC) laser structures offer attractive potential for operation at room temperature as both broadband coherent sources of mid-infrared light and fast photodetectors. This makes the realization of extremely compact spectrometers on a monolithic platform possible, and even dual-comb spectroscopy (DCS) configurations. IC comb devices are perfect candidates for this configuration, since they develop near-THz-wide optical frequency comb spectra from a millimeter-sized cavity, using a multi-stage structure that can also function as a very fast photodetector. In this work, we leverage IC photodetectors with a gigahertz bandwidth to demonstrate a self-contained, free-running, room-temperature DCS system in the mid-infrared. The DCS system used detection by the same bi-functional IC device structure to measure 1,1-difluoroethane over ∼600 GHz of optical coverage around 3.6 µm. These results show that the IC platform is suitable for full integration as a broadband, high-resolution on-chip spectrometer in a future chemical sensing system. [ABSTRACT FROM AUTHOR]

Due to growth temperature differences during deposition of GaN heterostructures utilizing InAlN barriers, an inadvertent parasitic GaN layer can form in the InAlN barrier layer. In structures utilizing AlN spacer layers, this parasitic layer acts as a second conduction channel with a carrier density dependent upon polarization charges and lattice strain as well as the surface potential. The effect of an additional GaN spacer layer in InAlN/AlN/GaN structures is assessed using simulations, electron-microscopy observations, magnetoconductivity measurements with gated Hall bar samples, and with quantitative mobility spectrum analysis. We propose a possible formation mechanism for the parasitic layer, and note that although the additional unintended layer may have beneficial aspects, we discuss a strategy to prevent its occurrence. [ABSTRACT FROM AUTHOR]

Magnetotransport measurements in pulsed fields up to 15 T have been performed on mercury cadmium telluride (Hg1-xCdxTe, x∼0.2) bulk as well as liquid phase epitaxially grown samples to obtain the resistivity and conductivity tensors in the temperature range 220–300 K. Mobilities and densities of various carriers participating in conduction have been extracted using both conventional multicarrier fitting (MCF) and mobility spectrum analysis. The fits to experimental data, particularly at the highest magnetic fields, were substantially improved when MCF is applied to minimize errors simultaneously on both resistivity and conductivity tensors. The semiclassical Boltzmann transport equation has been solved without using adjustable parameters by incorporating the following scattering mechanisms to fit the mobility: ionized impurity, polar and nonpolar optical phonons, acoustic deformation potential, and alloy disorder. Compared to previous estimates based on the relaxation time approximation with outscattering only, polar optical scattering and ionized impurity scattering limited mobilities are shown to be larger due to the correct incorporation of the inscattering term taking into account the overlap integrals in the valence band. [ABSTRACT FROM AUTHOR]

The light extraction efficiency of an organic light-emitting diode (OLED) was significantly enhanced upon incorporating a photonic-crystal (PC) pattern consisting of ZnS pillars residing on top of the transparent anode-glass substrate. The luminance efficiency of the PC-OLED is enhanced by a factor of 2.1 to 2.4 depending on the periodicity of the PC structure, when compared to that of a control OLED operating under the same conditions. [ABSTRACT FROM AUTHOR]

Dilute-nitride GaNSb bulk materials with up to 1.4% nitrogen were grown by molecular beam epitaxy on GaSb substrates. Hall measurements indicate residual hole concentrations of nearly 1019 cm-3 at room temperature, but a decrease to below 1016 cm-3 and a hole mobility of 1300 cm2/V s at 4.5 K for a sample with 0.6% nitrogen. Photoluminescence (PL) and optical absorption measurements demonstrate a bandgap reduction by up to 300 meV with increasing nitrogen incorporation. The experimental absorption spectra are well fit by a functional dependence corresponding to direct allowed optical transitions, and the PL spectra are also consistent with that interpretation. Room temperature carrier relaxation times in the picosecond range are measured using an ultrafast PL upconversion technique. [ABSTRACT FROM AUTHOR]

We employ a cavity-length study to determine the temperature variation of the internal loss and gain per unit current density in a ten-stage interband cascade laser that operated cw up to 269 K with an emission wavelength of 4.05 μm. The characteristic temperature for the gain per unit current density is 39 K, which is slightly lower than T0 of the threshold current and is consistent with dominance by Auger recombination. The internal loss for the 150-μm-wide mesa devices increased from 11 cm-1 at 78 K to 28 cm-1 at 275 K. [ABSTRACT FROM AUTHOR]

Pseudomorphic four-period GaAs0.978N0.022/GaAs0.78Sb0.22 type-II multiquantum well structures were grown on (100) GaAs substrates by metalorganic vapor phase epitaxy at 530 °C. The GaAs0.978N0.022 layers were grown at a V/III ratio of 685 and N/V ratio of 0.96, whereas the GaAs0.78Sb0.22 was grown at a V/III ratio of 3.8 and Sb/V ratio of 0.8. The superlattice peaks in the x-ray diffraction θ-2θ scans around the (400) GaAs peak were fitted using a dynamical simulation model to determine layer thickness and alloy compositions. The GaAsN and GaAsSb thicknesses were ∼8 nm and ∼5 nm, respectively. The photoluminescence (PL) spectra were obtained at 30 K and the PL peak energy was found to match the type-II transition energy obtained from a 10-band k·p model. Postgrowth annealing under arsine-H2 with a N2 cooldown was found to increase the low temperature PL intensity and result in the appearance of luminescence at room temperature. [ABSTRACT FROM AUTHOR]

We measured and modeled the performance characteristics of a distributed-feedback quantum-cascade laser exhibiting high-power continuous-wave (CW) operation in a single spectral mode at λ≈4.8 μm and temperatures up to 333 K. The sidemode suppression ratio exceeds 25 dB, and the emission remains robustly single mode at all currents and temperatures tested. CW output powers of 99 mW at 298 K and 357 mW at 200 K are obtained at currents well below the thermal rollover point. The slope efficiency and subthreshold amplified spontaneous emission spectra are shown to be consistent with a coupling coefficient of no more than κL≈4–5, which is substantially lower than the estimate of 9 based on the nominal grating fabrication parameters. [ABSTRACT FROM AUTHOR]

An optical parametric oscillator is tuned to the resonance wavelength of the etalon in an optical pumping injection cavity (OPIC) laser with a type-II “W” active region, thereby minimizing the threshold pump intensity and maximizing the output slope efficiency. Previous OPIC experiments employed fixed-wavelength sources with only limited tuning available by adjusting the incident angle. Low threshold pump intensities of 330 W/cm2 at 100 K and 14 kW/cm2 at 300 K (where the output wavelength is 3200 nm) were achieved. The energy conversion efficiency is found to decrease by over a factor of 100 when the pump wavelength is tuned from the resonance condition (1822 nm at 300 K) to only slightly off resonance (e.g., 1808 nm). [ABSTRACT FROM AUTHOR]

We have studied how the photoluminescence (PL) and lasing characteristics of mid-IR type II "W" [InAs/Ga[sub 1-x]In[sub x]Sb/InAs/AlAs[sub y]Sb[sub 1-y]] structures depend on the molecular beam epitaxy growth conditions. The growth temperature that yields the highest PL intensities and narrowest PL lines is found to be in the ≈480-510 °C range, which is considerably higher than the temperatures used in previous type II antimonide laser growths. Also contrary to earlier reports is our observation that using migration-enhanced epitaxy to force an InSb-like interface bond type is detrimental to the laser performance. The PL intensity at 78 K is found to correlate closely with the PL intensities and linewidths at all temperatures, as well as the lasing linewidths, thresholds, and efficiencies. Even though the tested laser structures were grown at a nonoptimal lower substrate temperature of 425 °C, they nonetheless yielded much better morphology, better-resolved x-ray features, stronger PL intensities, narrower PL linewidths, lower lasing thresholds (<200 W/cm² at 78 K), lower internal losses (<5 cm[sup -1] at 78 K), and longer Shockley-Read lifetimes (>20 ns at 78 K) than any previous antimonide lasers grown on the present Riber 32P molecular beam epitaxy system. [ABSTRACT FROM AUTHOR]

Presents information pertaining to the theoretical investigation regarding the internal losses in optically pumped type-II lasers. Moderation of losses; What the comparison of detailed numerical simulation showed; Information on the calculations of the temperature-dependent intervalence absorption cross section; Details on theoretical investigations.

Presents a study which determined free-carrier effective masses in mercury telluride-cadmium telluride superlattices using measurements of oscillatory magnetoresistance. Agreement of the study findings with the predictions of band-structure theory; Details of the Shubnikov-de Haas oscillations in both n- and p-type mercury telluride-cadmium telluride superlattices.

Longwave infrared detectors using p-type absorbers composed of InAs-rich type-II superlattices (T2SLs) nearly always suffer from high surface currents due to carrier inversion on the etched sidewalls. Here, we demonstrate reticulated shallow etch mesa isolation (RSEMI): a structural method of reducing surface currents in longwave single-band and midwave/longwave dual-band detectors with p-type T2SL absorbers. By introducing a lateral shoulder to increase the separation between the n+ cathode and the inverted absorber surface, a substantial barrier to surface electron flow is formed. We demonstrate experimentally that the RSEMI process results in lower surface current, lower net dark current, much weaker dependence of the current on bias, and higher uniformity compared to mesas processed with a single deep etch. For the structure used, a shoulder width of 2 μm is sufficient to block surface currents. [ABSTRACT FROM AUTHOR]

We report interband cascade vertical-cavity surface-emitting lasers (ICVCSELs) that operate in pulsed mode at temperatures up to 70 °C. Their emission at λ ≈ 3.4 lm extends considerably the previous longest wavelength of 3.0 lm for an electrically-pumped vertical-cavity surface-emitting laser operating at room temperature. The output from mesas having diameters ranging from 30 to 60 μm (with emission aperture diameters of 20-50 μm) is circularly symmetric, and the threshold current densities at T=25 °C are as low as 390 A/cm2. However, the differential slope efficiencies are low, e.g., ⩽50 mW/A at T=25 °C, due to loss in the top and bottom mirrors and reduced current efficiency. The smallest device operates in a single spectral mode despite having an emission aperture much wider than the wavelength. [ABSTRACT FROM AUTHOR]

Broad-area 10-stage interband cascade lasers (ICLs) emitting at λ = 3.0-3.2 μm are shown to maintain continuous-wave (cw) wallplug efficiencies exceeding 40% at temperatures up to 125 K, despite having a design optimized for operation at ambient and above. The cw threshold current density at 80 K is only 11 A/cm² for a 2 mm cavity with anti-reflection/high-reflection coatings on the two facets. The external differential quantum efficiency for a 1-mm-long cavity with the same coatings is 70% per stage at 80 K, and still above 65% at 150 K. The results demonstrate that at cryogenic temperatures, where free carrier absorption losses are minimized, ICLs can convert electrical to optical energy nearly as efficiently as the best specially designed intersubband-based quantum cascade lasers. [ABSTRACT FROM AUTHOR]

We report on the performance and reliability of laterally-coupled distributed-feedback (DFB) interband cascade lasers designed to operate at 3.6 μm wavelength. A two-step ridge etch process ensures single-transverse-mode operation with minimal lateral current spreading, and a secondorder Bragg grating etched alongside the ridge waveguide imposes single-mode DFB operation. Life tests performed on four randomly selected lasers, continuously operating at 40 °C with output power >10 mW, showed no measurable degradation after each laser was operated continuously for more than 1500 h. [ABSTRACT FROM AUTHOR]

In this paper, we describe functional anomalies induced by the atmospheric radiation environment in flight balloon during polar vortex and equatorial operational campaigns. These anomalies are the consequence of single event effects (SEE) and are characterized by over-current events on electronic boards inducing the inability to enter into communication. Objectives of this paper consist of describing and analyzing data issued from operational in-flight, then to demonstrate that radiations are the origin of anomalies. High-energy neutron operational campaign (Uppsala) and SEE high-energy proton test at device level (KVI) were performed. Modeling approaches were proposed and results are compared with in-flight data. Then, this work demonstrates the operational impact induced by neutron and proton environments on electronic balloon board and proposes modeling and experimental approaches to quantify the SEE risk. [ABSTRACT FROM PUBLISHER]

We demonstrate incoherent light emission peaked at λ = 3.3 μm from a 15-stage interband cascade active region. The interband cascade light emitting devices with mesa diameters ranging from 50 to 400 μm were mounted epitaxial-side-down, and light was extracted from the substrate side. At an applied bias of 8.7V and injection current of 0.6 A, and without any measures taken to improve the poor out-coupling efficiency caused by total internal reflection, a 400-μm-diameter device produced 1.6 mW of continuous-wave output power at T = 25°C. Mesas with smaller diameters displayed emission intensities as high as 1.7 W/cm². [ABSTRACT FROM AUTHOR]

We report tapered-ridge mid-infrared (λ = 3.75 μm) interband cascade lasers emitting up to 403 mW of continuous wave output power at T = 25 °C, with beam quality characterized by M2 = 2.3. One index-guided tapered structure consisted of a single 4-mm-long section with ridge width varying linearly from 5 μm to 63 μm. Another device that combined a narrow ridge of uniform width with a tapered section produced slightly lower maximum output power and brightness. [ABSTRACT FROM AUTHOR]

We discuss the single-mode performance characteristics of midwave-infrared interband cascade lasers. Broad-area devices with 5 active stages display pulsed threshold current densities as low as 375 A/cm2 and threshold power densities as low as 920 W/cm2 at room temperature, owing in part to the suppression of Auger recombination. Narrow ridges were processed using optical lithography to incorporate a periodically-corrugated pattern into the sidewalls. The corrugations are intended to suppress lasing in higher-order lateral modes, and also provide a 4th-order grating for distributed feedback. A corrugated-sidewall device operating at T = -20° produced more than 46 mW of cw output in a single spectral mode, with a peak wallplug efficiency of 7.6%. The device maintains single-mode operation at current densities up to 10 times the lasing threshold, and the single-mode tuning range is 26 nm if both current and temperature are varied. Another device operating at -23°C produces up to 31 mW of single-mode power in the 3.3142-3.3164 μm range that spans several of the strongest absorption signature lines for methane. [ABSTRACT FROM AUTHOR]

Lateral structure is investigated in two antimonide superlattices using x-ray diffraction. We report periodic lateral modulation in AlSb/AlAs digital superlattices, while no lateral modulation is observed in similar InAs/Al(In)Sb digital superlattices. By fitting the diffraction data with dynamical diffraction theory we are able to determine the strain in each layer and at the interfaces. The findings are consistent with recent predictions of the critical thickness for three-dimensional growth. [ABSTRACT FROM AUTHOR]

We discuss the state-of-the-art performance of interband cascade lasers emitting in the 3-5 μm spectral band. Broad-area devices with five active stages display pulsed threshold current densities as low as 400 A cm-2 at room temperature. Auger decay rates are extracted from the analysis of threshold current densities and differential slope efficiencies of nearly 30 lasers, and found to be significantly lower than was anticipated based on prior information. New designs also produce ICLs with room-temperature internal losses as low as ≈6 cm-1. The combination of these advances with improvements to the processing of narrow ridges has led to the fabrication of a 4.4-μm-wide ridge emitting at 3.7 μm that lased to 335K in continuous mode. This is the highest continuous-wave (cw) operating temperature for any semiconductor laser in the 3.0-4.6 μm spectral range. A 10-μm-wide ridge with high-reflection and antireflection facet coatings produced up to 59 mW of cw power at 298 K, and displayed a maximum wall-plug efficiency of 3.4%. [ABSTRACT FROM AUTHOR]

Heterostructures with a single InAs[sub 1-x]Sb[sub x]/AlSb[sub 1-y]As[sub y] quantum well (QW) on (001) GaSb substrates have been grown by MBE and studied using X-ray diffraction, transmission electron microscopy, and photoluminescence (PL) spectroscopy. High-intensity PL was observed at a temperature of 80 K, with a peak half-width of 30-50 meV and a peak wavelength in the range from 2 to 4.5 µm, depending on the QW width, which varied between 4 and 20 nm, respectively. The fundamental absorption edge of such QWs was calculated for a wide range of alloy compositions, x and y. Good correlation between the experimental and calculated dependences of the band gap on the InAsSb/AlSbAs QW thickness was obtained. [ABSTRACT FROM AUTHOR]