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ULTRARAM™ is a non-volatile memory with the potential to achieve fast, ultra-low-energy electron storage in a floating gate accessed through a triple-barrier resonant tunnelling heterostructure. Here we report the implementation of ULTRARAM™ on a Si substrate; a vital step towards cost-effective mass production. Sample growth was carried out using molecular beam epitaxy, by first depositing an AlSb nucleation layer to seed the growth of a GaSb buffer layer, followed by the III-V memory epilayers. Fabricated single-cell memories show clear 0/1 logic-state contrast after ≤10-ms duration program/erase pulses of ~2.5 V, a remarkably fast switching speed for 10- and 20-µm devices. Furthermore, the combination of low voltage and small device capacitance per unit area results in a switching energy that is orders of magnitude lower than dynamic random access memory and flash, for a given cell size. Extended testing of the devices revealed retention in excess of 1000 years and degradation-free endurance of over 107 program/erase cycles, exceeding very recent results for similar devices on GaAs substrates.

Thermophotovoltaic (TPV) devices based on GaInAsSb lattice matched to GaSb (100) substrates have demonstrated high external quantum efficiencies (EQEs) in the mid-infrared spectral range, making them promising candidates for waste heat recovery from high temperature “blackbody” sources. In this work, the GaInAsSb alloy has been integrated onto more cost-effective GaAs (100) substrates by using advanced metamorphic buffer layer techniques in molecular beam epitaxy (MBE), which included an interfacial misfit (IMF) array at the GaSb/GaAs interface followed by GaInSb/GaSb dislocation filtering layers. The threading dislocations in the GaInAsSb region can be efficiently supressed, resulting in high quality materials for TPV applications. To determine the performance of the GaInAsSb TPV on GaAs it was compared with a cell grown lattice matched onto GaSb substrate having the same structure. The resulting TPV on GaAs exhibited similar dark current-voltage characteristics with that on GaSb. Under illumination from an 800 °C silicon nitride emitter, the short circuit current density (Jsc) from the GaInAsSb TPVs on GaAs reached more than 90% of the control cell on GaSb, and the open circuit voltage (Voc) exceeded 80% of the cell on GaSb. The EQE from the TPV on GaAs reached around 62%, the highest value reported from this type of TPV on GaAs. With improved TPV structure design, large area GaInAsSb TPV panels on GaAs substrates can be realized in the future for waste heat energy recovery applications.

GaSb-based materials can be used to produce high performance photonic devices operating in the technologically important mid-infrared spectral range. Direct epitaxial growth of GaSb on silicon (Si) is an attractive method to reduce manufacturing costs and opens the possibility of new applications, such as lab-on-a-chip MIR photonic integrated circuits and monolithic integration of focal plane arrays (FPAs) with Si readout integrated circuits (ROICs). However, fundamental material dissimilarities, such as the large lattice mismatch, polar-nonpolar character of the III-V/Si interface and differences in thermal expansion coefficients lead to the formation of threading dislocations and antiphase domains, which effect the device performance. This work reports on the molecular beam epitaxial growth of high quality GaSb-based materials and devices onto Si. This was achieved using a novel growth procedure consisting of an efficient AlSb interfacial misfit array, a two-step GaSb growth temperature procedure and a series of dislocation filter superlattices, resulting in a low defect density, anti-phase domain free GaSb buffer layer on Si. A nBn barrier photodetector based on a type-II InAs/InAsSb superlattice was grown on top of the buffer layer. The device exhibited an extended 50 % cut-off wavelength at 5.40 μm at 200 K which moved to 5.9 μm at 300 K. A specific detectivity of 1.5 x1010 Jones was measured, corresponding in an external quantum efficiency of 25.6 % at 200 K.

Silicon photonics has emerged as the most promising technology for next-generation compact optoelectronic systems, but further development is still required to achieve efficient and reliable on-chip light sources. Direct epitaxial growth of antimonide-based compound semiconductor materials on silicon provides a pathway toward the monolithic integration of new, mid-infrared solid-state light sources and comprehensive photonic circuits on silicon platforms. Such devices have wide-ranging applications in environmental monitoring and medical diagnostics. This paper reports on the realization of a mid-infrared InAsSb light emitting diode directly integrated onto silicon using molecular beam epitaxy. The heteroepitaxial integration of the InAsSb p-i-n device onto silicon was achieved with the use of a novel, antiphase domain-free, GaSb-on-silicon buffer layer. The device exhibited efficient light emission at room temperature, peaking at around 4.5 μm, which corresponds well to the CO2 atmospheric absorption band. An output power of 6 μW and an external quantum efficiency of 0.011% was measured at 300 K. These results demonstrate mid-infrared III-V light emitting diodes can be directly grown on silicon, which is an essential step towards the realization of the next generation, on-chip integrated light sources.

InAs thermophotovoltaic (TPV) cells with external quantum efficiency at the peak wavelengths reaching 71% at low temperature and 55% at room temperature are reported, which are the highest values to date for InAs. The TPV exhibited 10% power conversion efficiency at 100 K cell temperature. The dark and light current-voltage characteristics were measured at different cell temperatures (100–340 K) in response to heat sources in the range 500–800 °C. The resulting dependences of the output voltage and current as well as the spectral response of the InAs TPV have been extensively characterized for waste heat recovery applications. The performance of these cells is strongly determined by the dark current which increases rapidly with increasing cell temperature originating from bandgap narrowing, which resulted in a reduction of open circuit voltage and output power.

We report on the first single-junction GaSb solar cell epitaxially grown on a Si substrate. A control stand-alone GaSb solar cell was primarily fabricated, which demonstrated a 5.90% efficiency (AM1.5G). The preparation, growth and manufacturing procedures were then adapted to create the GaSb-on-Si solar cell. The hybrid device resulted in a degraded efficiency for which comparison between experimental and simulated data revealed dominant non-radiative recombination processes. Material and electrical characterization also highlighted the impact of anti-phase domains and boundaries and threading dislocation density on the shunt resistance of the cell. Nevertheless, the GaSb-on-Si cell performance is close to recent results on the integration of GaSb solar cells on GaAs, despite a much larger lattice mismatch (12% vs 8%). Routes for improvement, concerning the material quality and cell structure, are proposed. This work lays the foundations of a GaSb-based multi-junction solar cell monolithically integrated on Si.

Direct integration of III–V semiconductor light sources on silicon is an essential step toward the development of portable, on-chip infrared sensor systems. Driven by the presence of characteristic molecular fingerprints in the mid-infrared (MIR) spectral region, such systems may have a wide range of applications in infrared imaging, gas sensing, and medical diagnostics. This paper reports on the integration of an InAs virtual substrate and high crystalline quality InAs/InAsSb multi-quantum wells on Si using a three-stage InAs/GaSb/Si buffer layer. It is shown that the InAs/GaSb interface demonstrates a strong dislocation filtering effect. A series of strained AlSb/InAs dislocation filter superlattices was also used, resulting in a low surface dislocation density of approximately 4 × 107 cm−2. The InAs/InAsSb wells exhibited a strong photoluminescence signal at elevated temperatures. Analysis of these results indicates that radiative recombination is the dominant recombination mechanism, making this structure promising for fabricating MIR Si-based sensor systems.

We report on a mid-infrared resonant cavity light emitting diode (RCLED) operating at the wavelength of 4.5 µm with a narrow spectral linewidth at room temperature. Compared to a reference LED without a resonant cavity, our RCLED exhibits (85x) higher peak intensity, (13x) higher integrated output power, (16x) narrower spectral linewidth and (7x) superior temperature stability. The device consists of a one-wavelength thick micro-cavity containing an Al0.12In0.88As/InAs0.85Sb0.15 quantum well active region sandwiched between two high contrast AlAs0.08Sb0.92/GaSb distributed Bragg reflector mirrors, grown lattice–matched on GaSb by molecular beam epitaxy. The high spectral brightness, narrow linewidth and superior temperature stability are attractive features, enabling these devices to be used for detection of N2O at 4.5 µm. We show that with only minor adjustments the gases CO2 (4.2 µm) and CO (4.6 µm) are also readily accessible.

Mid-infrared (MIR) silicon photonics holds the potential for realizing next generation ultracompact spectroscopic systems for applications in gas sensing, defense, and medical diagnostics. The direct epitaxial growth of antimonide-based compound semiconductors on silicon provides a promising approach for extending the wavelength of silicon photonics to the longer infrared range. This paper reports on the fabrication of a high performance MIR photodetector directly grown onto silicon by molecular beam epitaxy. The device exhibited an extended cutoff wavelength at ∼5.5 μm and a dark current density of 1.4 × 10–2 A/cm2 under 100 mV reverse bias at 200 K. A responsivity of 0.88 A/W and a specific detectivity in the order of 1.5 × 1010 Jones was measured at 200 K under 100 mV reverse bias operation. These results were achieved through the development of an innovative structure which incorporates a type-II InAs/InAsSb superlattice-based barrier nBn photodetector grown on a GaSb-on-silicon buffer layer. The difficulties in growing GaSb directly on silicon were overcome using a novel growth procedure consisting of an efficient AlSb interfacial misfit array, a two-step growth temperature procedure and dislocation filters resulting in a low defect density, antiphase domain free GaSb epitaxial layer on silicon. This work demonstrates that complex superlattice-based MIR photodetectors can be directly integrated onto a Si platform, which provides a pathway toward the realization of new, high performance, large area focal plane arrays and mid-infrared integrated photonic circuits.

The capture cross-section, intersubband optical cross-section and non-radiative emission rates related to localized hole states are obtained for p-i-n solar cells containing GaSb/GaAs quantum rings embedded within the i-region of the device. The technique developed uses the intraband photoemission current to probe the charge state of the nanostructures during two-color excitation. Analysis of the excitation power dependence revealed a non-radiative hole capture lifetime of 12 ns under low excitation conditions, with high injection leading to the saturation of the hole occupancy within the quantum-rings. The decay characteristics of the optical hole emission current has also been exploited to determine the spectral and temperature dependence of the radiative and non-radiative hole escape mechanisms from the quantum-rings.

The qHAADF method allows the quantification of the composition at atomic column resolution in semiconductor materials by comparing the HAADF-STEM intensities between a region of interest to a region of the material of known composition. However, the application of this qHAADF approach requires both regions to be differentiable and included in the same micrograph at close proximity. This limits the application of this approach to certain materials and magnifications where this requirement is fulfilled. In this work, we extend the qHAADF method to analyses where the reference region is imaged in a separate micrograph. The validity of this modified method is proved by comparison to the original qHAADF approach using HAADF-STEM simulated images of the semiconductor heterostructure InSb/InAs. Additionally, the methods are applied successfully to experimental images both of a simple InSb/InAs interface and of a complex InSb/GaSb heterostructure, justifying the significance of the modified method over the original method.

Hydrostatic pressure can be used as a powerful diagnostic tool to enable the study of lattice dynamics, defects, impurities and recombination processes in a variety of semiconductor materials and devices. Here we report on intermediate band GaAs solar cells containing GaSb quantum rings which exhibit a 15% increase in open-circuit voltage under application of 8 kbar hydrostatic pressure at room temperature. The pressure coefficients of the respective optical transitions for the GaSb quantum rings, the wetting layer and the GaAs bulk, were each measured to be ~ 10.5 ± 0.5 meV/kbar. A comparison of the pressure induced and temperature induced bandgap changes highlights the significance of the thermal energy of carriers in intermediate band solar cells.

We report on the open-circuit voltage recovery in GaSb quantum ring (QR) solar cells under high solar concentration up to 2500 suns. The detailed behaviour of type II GaSb/GaAs QR solar cells under solar concentration, using different temperatures and light illumination conditions, is analysed through optical and electrical measurements. Although enhancement of the short-circuit current was observed because of sub-bandgap photon absorption in the QR, the thermionic emission rate of holes was found to be insufficient for ideal operation. The direct excitation of electron–hole pairs into QRs has revealed that the accumulation of holes is one of the causes of the open-circuit voltage (VOC) degradation. However, using concentrated light up to 2500 suns, the GaSb QR cell showed much quicker VOC recovery rate than a GaAs control cell.

There is considerable interest in the development of InAsSb-based nanowires for infrared photonics due to their high tunability across the infrared spectral range, high mobility, and integration with silicon electronics. However, optical emission is currently limited to low temperatures due to strong nonradiative Auger and surface recombination. Here, we present a new structure based on conical type II InAsSb/InAs multiquantum wells within InAs nanowires which exhibit bright mid-infrared photoluminescence up to room temperature. The nanowires are grown by catalyst-free selective area epitaxy on silicon. This unique geometry confines the electron-hole recombination to within the quantum wells which alleviates the problems associated with recombination via surface states, while the quantum confinement of carriers increases the radiative recombination rate and suppresses Auger recombination. This demonstration will pave the way for the development of new integrated quantum light sources operating in the technologically important mid-infrared spectral range.

We analyse the optical properties of InAs1−x Sb x /Al y In1−y As quantum wells (QWs) grown by molecular beam epitaxy on relaxed Al y In1−y As metamorphic buffer layers (MBLs) using GaAs substrates. The use of Al y In1−y As MBLs allows for the growth of QWs having large type-I band offsets, and emission wavelengths >3 m. Photoluminescence (PL) measurements for QWs having Sb compositions up to x = 10% demonstrate strong room temperature PL up to 3.4 m, as well as enhancement of the PL intensity with increasing wavelength. To quantify the trends in the measured PL we calculate the QW spontaneous emission (SE), using a theoretical model based on an eight-band Hamiltonian. The theoretical calculations, which are in good agreement with experiment, identify that the observed enhancement in PL intensity with increasing wavelength is associated with the impact of compressive strain on the QW valence band structure, which reduces the band edge density of states making more carriers available to undergo radiative recombination at fixed carrier density. Our results highlight the potential of type-I InAs1−x Sb x /Al y In1−y As metamorphic QWs to address several limitations associated with existing heterostructures operating in the mid-infrared, establishing these novel heterostructures as a suitable platform for the development of light-emitting diodes and diode lasers.

The authors report on the structural, the optical and the electrical properties of solar cells containing 20 layers of doped InAs/GaAs quantum dots (QDs). The structures were grown by molecular beam epitaxy and contain n dopant sheet densities of 8 and 16 × 1010cm−2, respectively, in between the QD layers. Under a 1 sun illumination, the open-circuit voltage (V oc) and the efficiency of the 8 × 1010cm−2 n-doped sample were increased to values of 0.73 V and 9.7%, respectively, compared with a reference undoped sample (a V oc of 0.70 V and an efficiency of 9.0%). However, the short-circuit current density (J sc) decreased from 20.1 to 17.4 mA/cm2 indicating bandfilling within the QD array.

The authors report on the analysis of the hole escape mechanisms from type-II GaSb quantum rings (QRs) embedded within the active region of a GaAs single junction solar cell. When the solar cell is excited by using a 1064 nm infrared laser with excitation energy lower than the bandgap of the GaAs matrix, photogenerated electron-hole pairs are created directly within the GaSb QRs. The QR photocurrent exhibits a linear dependence on the excitation intensity over several decades. The thermal activation energy was found to be weakly dependent on the incident light level and increased by only a few meV over several orders of excitation intensity. The magnitude of the relative absorption in the author's QRs when directly probed by using a 1064 nm laser with an incident power density of approximate to 2.6 W cm(-2) is found to be approximate to 1.4 x 10(-4) per layer. The thermal escape rate of the holes was calculated and found to be approximate to 10(11) to 10(12) s(-1), which is much faster than the radiative recombination rate 10(9) s(-1). This behaviour is promising for concentrator solar cell development and has the potential to increase solar cell efficiency under a strong solar concentration.

Novel InSb quantum dot (QD) nanostructures grown by molecular beam epitaxy (MBE) are investigated in order to improve the performance of light sources and detectors for the technologically important mid-infrared (2-5 μm) spectral range. Unlike the InAs/GaAs system which has a similar lattice mismatch, the growth of InSb/InAs QDs by MBE is a challenging task due to Sb segregation and surfactant effects. These problems can be overcome by using an Sb-As exchange growth technique to realize uniform, dense arrays (dot density ~1012 cm-2) of extremely small (mean diameter ~2.5 nm) InSb submonolayer QDs in InAs. Light emitting diodes (LEDs) containing ten layers of InSb QDs exhibit bright electroluminescence peaking at 3.8 μm at room temperature. These devices show superior temperature quenching compared with bulk and quantum well (QW) LEDs due to a reduction in Auger recombination. We also report the growth of InSb QDs in InAs/AlAsSb ‘W’ QWs grown on GaSb substrates which are designed to increase the electron-hole (e-h) wavefunction overlap to ~75%. These samples exhibit very good structural quality and photoluminescence peaking near 3.0 μm at low temperatures.

La Loi sur le systeme de justice penale pour les adolescents (2003) a ete promulguee dans le but de diminuer le recours aux tribunaux et a la detention pour les jeunes contrevenants, et a ameliorer l’efficacite des mesures prises dans les cas de violence criminelle grave commise par des jeunes. Dans l’article, on evalue l’impact qu’a eu la Loi au cours des cinq annees suivant son adoption. On y passe en revue les principales dispositions de la Loi touchant la determination de la peine et les mesures extrajudiciaires. On y parle aussi de la jurisprudence de la Cour supreme du Canada quant a l’interpretation de la Loi et on presente des donnees statistiques sur l’impact qu’a eu la Loi sur les mesures extrajudiciaires et la determination de la peine chez les adolescents, ainsi que sur le nombre de cas juges devant les tribunaux et en detention. La Cour supreme a interprete de maniere restrictive les dispositions de la Loi permettant de recourir a la detention, ce qui a contribue a faire diminuer le taux de detention. La Cour a aussi insiste sur le fait qu’il faut traiter les jeunes differemment des adultes. De plus, elle a juge inconstitutionnelles les dispositions de la Loi creant une presomption de peine applicable aux adultes pour les jeunes contrevenants les plus violents, limitant ainsi les effets de certains articles de la Loi visant les crimes graves avec violence. Grâce a la Loi, le taux de recours aux tribunaux et a la detention ont considerablement diminue, sans que la criminalite enregistree chez les jeunes augmente pour autant. Il existe encore des variations importantes d’une region a l’autre du recours aux tribunaux de la jeunesse et de detention chez les jeunes. Meme s’il y a moins de differences regionales liees au recours aux tribunaux depuis l’adoption de la Loi, il n’y a pas vraiment eu de changement quant a la detention apres son entree en vigueur. La criminalite chez les jeunes demeure un sujet de preoccupation politique litigieux au Canada. Abstract: The Youth Criminal Justice Act (2003) was enacted with the intent of decreasing the use of courts and restricting the use of custody for adolescent offenders, while improving the effectiveness of the responses to serious violent youth offenders. This paper assesses the impact of the act in its first five years. It reviews salient provisions of the act dealing with sentencing and diversion, discusses Supreme Court of Canada jurisprudence interpreting the act, and presents statistical data on the impact of the YCJA on diversion and sentencing of youth and on youth court and custodial caseloads. The Supreme Court has narrowly interpreted the provisions of the YCJA that allow for the use of custody, contributing to a reduction in use of custody. The Court has also emphasized that youth are to be treated differently from adults and ruled unconstitutional provisions of the YCJA that created a presumption of adult sentencing for the most serious offences by young offenders, limiting the effect of provisions of the act directed at serious violent offenders. The YCJA has succeeded in significantly reducing the rates of use of court and custody, without increasing recorded youth crime. There continue to be significant regional variations in rates of use of youth courts and custody. Although regional differences in the use of court have declined under the YCJA, variation in the use of custody has not been significantly affected by the new act. Youth crime remains a contentious political concern in Canada.

GaSb p–i–n photodiodes were grown on GaAs and Si, using interfacial misfit arrays, and on native GaSb. For the samples grown on GaAs and Si, high-resolution transmission electron microscopy images revealed interface atomic periodicities in agreement with atomistic modeling. Surface defect densities of ~View the MathML source were measured for both samples. Atomic force microscopy scans revealed surface roughnesses of around 1.6 nm, compared with 0.5 nm for the sample grown on native GaSb. Dark current and spectral response measurements were used to study the electrical and optoelectronic properties of all three samples.

The concept of social exclusion is used to explore the relationship between people and groups who are socially and economically disadvantaged and the phenomenon of going missing. Police data about missing persons are compared to census data to determine whether groups who experience family dissolution, labour market exclusion, and other forms of disadvantage and social exclusion are overrepresented among missing persons compared to the general population. The analysis shows that disadvantaged youth, women, Aboriginal people, people who are not in the labour force, unemployed people, and homeless people are all overrepresented among missing persons. People occupying the intersections of multiple high risk categories are at particularly high risk of going missing. Linking missing persons with the concept of social exclusion shows that social and economic disadvantage lead directly and indirectly to peoples’ disappearances. (133 words)

Electroluminescence is reported from dilute nitride InAsSbN/InAs multiquantum well light-emitting diodes grown using nitrogen plasma source molecular beam epitaxy. The diodes exhibited bright emission in the midinfrared peaking at 3.56 μm at room temperature. Emission occurred from a type I transition from electrons in the InAsSbN to confined heavy and light hole states in the QW. Analysis of the temperature- and current-dependent electroluminescence shows that thermally activated hole leakage and Auger recombination are the performance limiting factors in these devices.

We present the results of an investigation into the growth of InGaSb/GaAs quantum dots (QDs) by molecular beam epitaxy using migration-enhanced epitaxy. Surface atomic force microscopy and cross-sectional transmission electron microscopy show that the QDs undergo a significant change in morphology upon capping with GaAs. A GaAs ‘cold capping’ technique was partly successful in preserving QD morphology during this process, but strong group V intermixing was still observed. Energy-dispersive x-ray spectroscopy reveals that the resulting nanostructures are small ‘core’ QDs surrounded by a highly intermixed disc. Temperature varying photoluminescence measurements indicate strong light emission from the QDs, with an emission wavelength of 1230 nm at room temperature. Nextnano 8x8 k.p calculations show good agreement with the PL results and indicate a low level of group-V intermixing in the core QD.

This paper tests hypotheses implicit in the societal-reaction perspective concerning the nature and pattern of the relationship between prior and current youth court dispositions. The dispositional stage is the most critical decision-making level which young offenders encounter in their contact with the youth court system. Previous research has produced inconsistent results in the attempt to determine which model or models of justice underlie dispositional decisions by youth court judges. Log-linear modeling is employed on 16,636 youth court cases in Canada in 1993/1994 to determine the nature and magnitude of the relationship between current and prior dispositions. The results indicate that prior youth court dispositions exert a significant impact on current dispositions, even when relevant variables are controlled. Evidence is found mainly of stabilization—the repetition of the same type of disposition—and also of escalation in dispositions. These findings provide support for the societal-reaction theory and possibly for the desert-based theory of sentencing.

This article demonstrates the innovative use of the log-linear distance model in the assessment of homophily in a set of small groups, such as the co-participants in a set of events. It traces the development of the application of the log-linear distance model to the study of homophily and reviews its recent use to assess the extent and structure of gender and age homophily in groups of criminal accomplices (‘co-offenders’). The transformations of the group membership data that are a prerequisite of the log-linear analysis, and the interpretation of the log-linear parameters, are explained in detail in order to make the approach accessible to potential users. Although the described applications are to gender and age homophily in groups of criminal accomplices, the method can be used to assess homophily on one or more variables in any small groups.

The aluminium-gallium-indium-antimonide (Al x Ga y In\({}_{1-x-y}\)Sb) material system offers great promise for efficient laser diode operation across the 3 to 5 μm wavelength range. It offers an excellent compromise between the requirements for good electronic and optical confinement and those for low series resistance. In addition, the use of an active region comprising compressively strained Type-I quantum wells (QWs) is predicted to lead to increased gain, which leads to lower threshold current densities and hence reduced non-radiative Auger recombination. In this paper a review of recent progress in the development of this material system is given, including the demonstration of multi-quantum well samples exhibiting photoluminescence up to room temperature, and laser diodes operating up to 219 K.

The influence of using a Bi surfactant during the growth of InAsSb on the composition was examined, and it was found that increasing Bi flux on the surface during growth inhibits the incorporation of Sb. Analysis of the data via a kinetic model of anion incorporation shows that surface Bi acts as a catalyst for InAs formation, thus inhibiting Sb incorporation.

In this study, the density of states associated with the localization of holes in GaSb/GaAs quantum rings are determined by the energy selective charging of the quantum ring distribution. The authors show, using conventional photocapacitance measurements, that the excess charge accumulated within the type-II nanostructures increases with increasing excitation energies for photon energies above 0.9 eV. Optical excitation between the localized hole states and the conduction band is therefore not limited to the Γ(k = 0) point, with pseudo-monochromatic light charging all states lying within the photon energy selected. The energy distribution of the quantum ring states could consequently be accurately related from the excitation dependence of the integrated photocapacitance. The resulting band of localized hole states is shown to be well described by a narrow distribution centered 407 meV above the GaAs valence band maximum.

The extended photo-response of solar cells containing ten periods of GaSb/GaAs quantum rings imbedded in the p-i-n junction has been described using a single-band representation of the type-II quantum ring structure. By fitting the experimental data, the authors were able to deduce that the quantum rings are well represented by a Gaussian height distribution and a large valence band discontinuity. The simulated band of states is shown to be well matched to the photoluminescence analysis of the structure, with the inhomogeneous size distribution resulting in a band of hole states roughly 390 meV above the valence band.

We have studied the ensemble photoluminescence (PL) of 11 GaSb/GaAs quantum dot/ring (QD/QR) samples over >= 5 orders of magnitude of laser power. All samples exhibit a blueshift of PL energy, Delta E, with increasing excitation power, as expected for type-II structures. It is often assumed that this blueshift is due to band-bending at the type-II interface. However, for a sample where charge-state sub-peaks are observed within the PL emission, it is unequivocally shown that the blueshift due to capacitive charging is an order of magnitude larger than the band bending contribution. Moreover, the size of the blueshift and its linear dependence on occupancy predicted by a simple capacitive model are faithfully replicated in the data. In contrast, when QD/QR emission intensity, I, is used to infer QD/QR occupancy, n, via the bimolecular recombination approximation (I alpha n(2)), exponents, x, in Delta E alpha I-x are consistently lower than expected, and strongly sample dependent. We conclude that the exponent x cannot be used to differentiate between capacitive charging and band bending as the origin of the blueshift in type-II QD/QRs, because the bimolecular recombination is not applicable to type-II QD/QRs. (C) 2013 AIP Publishing LLC.

We report on the epitaxial growth and photoluminescence (PL) of InAs0.926Sb0.063N0.011/InAs multi-quantum wells (QWs) grown using plasma-assisted molecular beam epitaxy. These dilute nitride QWs exhibit bright PL in the mid-infrared spectral range up to a temperature of 250 K without any post-growth annealing. Consideration of the power dependent PL behaviour is consistent with a type I band line-up in these QWs, arising from a strong lowering of the conduction band edge due to N-induced band anti-crossing effects.

Photoluminescence (PL) from GaInSb/AlInSb type I multi-quantum-wells, grown on GaAs, has been investigated as a function of strain in the quantum wells. Luminescence, between 3 and 4 mu m, was observed for all samples, with good agreement between the measured and calculated peak emission energies. Analysis of the temperature dependence of the luminescence suggests that population of excited quantum well hole subbands occurs at high temperature, leading to a reduction in the PL signal. Room temperature luminescence was obtained from a sample with similar to 0.8% strain in the quantum wells. Preliminary results from laser diodes fabricated from companion wafers indicate lasing up to 220 K

An improved InAsSb/InAsSbP double heterojunction ridge laser was designed and grown by liquid phase epitaxy. The cladding layer absorption loss was minimized by the introduction of two undoped quaternary layers on either side of the active region to form a five layer epitaxial structure. The inserted layers also helped alleviate interdiffusion of unwanted dopants into the active region and reduced current leakage in the device. The resulting diode lasers operate readily in pulsed mode near 3.5 µm at elevated temperatures and with a threshold current density as low as 118 A cm−2 at 85 K. Compared to the conventional three-layer double heterostructure laser, the modified structure with reduced optical loss increased the maximum lasing temperature by 95–210 K.

In his paper on transcendental intersubjectivity in Husserl, which refers mainly to the Fifth Cartesian Meditation, Schutz (1966a) marks out four stages in Husserl's argument and finds what are for him insurmountable problems in each stage. These stages are: (1) isolation of the primordial world of one's peculiar ownness by means of a further epoch?; (2) apperception of the other via pairing; (3) constitution of objective, intersubjective Nature; (4) constitution of higher forms of community. Because of the problems Schutz encounters in each of these stages, he concludes that Husserl's theory is unacceptable (Schutz, 1966a, p. 82). Having already proved that it is unacceptable, he now explains why these problems arise in Husserl's theory. Intersubjectivity, says Schutz, is "a datum of the life-world," (1966a, p. 82) not a transcendental problem. In other words, intersubjectivity must be dealt with as a problem of the life-world of the natural attitude, not a "problem of constitution which can be solved within the transcendental sphere." (Schutz, 1966a, p. 82). There is no such thing as transcendental intersubjectivity, if by that is meant intersubjectivity of a plurality of transcendental egos. The role of transcendental phenomen? ology in the problem of intersubjectivity is to explicate within the transcendental reduction the sense: "intersubjectivity in the life-world." Husserl was diverted from this proper role of phenomenology?in his words, to "explicate the sense which this world has for us prior to all philosophy" (trans, and quoted by Schutz from "Cartesianische Meditationen, para. 62, in fine, "in Schutz, 1966a, p. 82)?because of the unobtrusive transformation of sense of his concept of constitution from that of explication and clarification to "creation," in the sense of providing an ontology of the life world. The fact that phenomenology is in principle incapable of doing this lies behind the failure of Husserl's theory of intersubjectivity (Schutz, 1966a, pp. 83-84). Unlike Schutz, I will deal with this general issue explicitly in the context of the stages in Husserl's argument and Schutz's objections. It seems to me that

Sub-monolayer (SML) deposition of InSb within InAs matrix by migration enhanced epitaxy (MEE) tends to form type II SML nanostructures offering efficient light emission within the mid-infrared (MIR) range between 3-5 µm. In this work, we report on the Sb distribution in InSb/InAs SML nanostructures with InAs cap layers grown at temperatures lower than that associated with the under-grown InSb active layer. Analysis by transmission electron microscopy (TEM) in 002 dark field (DF) conditions shows that the reduction in the growth temperature of the InAs cap layer increases the amount of Sb deposited in the layers, in good agreement with the X-ray diffraction (XRD) results. TEM micrographs also show that the layers are formed by random InSbAs agglomerates, where the lower cap temperature leads to a more continuous InSb layer. Quantitative atomic column resolved high angle annular dark field (HAADF)-scanning (S)TEM analyses also reveal atomic columns with larger composition of Sb for the structure with the lowest InAs cap layer temperature. The dependence of the Sb distribution on InAs cap growth temperature allows tuning the corresponding emission wavelength in the MIR range, as shown by the photoluminescence (PL) emission spectra.

Kinship, like language, is a structure, not a substance. The distinctive features of kinship networks reside less in how their constitutive ties - be they biological, jural, ritual, symbolic, or whatever - are defined and established than in the way these ties are organized. Kinship network theory is thus not just another "application" of general network theoretic methods to a particular social domain but a specific branch of social network theory in itself, defined by its own axioms and described by its own theorems. This article sets out to present these axioms and theorems.