Ideal CdTe/HgTe superlattices

In this paper we consider a new superlattice system consisting of alternating layers of CdTe and HgTe constructed parallel to the (001) zincblende plane. The tight‐binding method is used to calculate the electronic properties of this system, in particular, band edge and interface properties. The energy gap as a function of layer thickness is determined. It is found to decrease monotonically with increasing HgTe layer thickness for a fixed ratio of CdTe to HgTe layer thicknesses. The symmetry of the valence band maximum state is found to change at certain HgTe layer thicknesses. This is explained by relating the superlattice states to bulk CdTe and HgTe states. The existence of interface states is investigated for the superlattice with 12 layers of CdTe alternating with 12 of HgTe. Interface states are found near the boundaries of the Brillouin zone, but none are found in the band gap

Localization of superlattice electronic states and complex bulk band structures

The relative lineup of the band structures of the two constituents of a semiconductor superlattice can cause charge carriers to be confined. This occurs when the energy of a superlattice state is located in an allowed energy region of one of the constituents (the "well" semiconductor), but in the band gap of the other (the "barrier" semiconductor). A charge carrier will tend to be confined in the layers made from the semiconductor with the allowed region at that energy. It will have an exponentially decaying amplitude to be found in the semiconductor with a band gap at that energy

Tight‐binding calculation for the AlAs–GaAs (100) interface

We report the results of a study of the electronic properties of the AlAs–GaAs interface using the tight‐binding method. The tight‐binding matrix for the superlattice system is used in the limit in which the thickness of the repeated superlattice slab becomes large. This system is studied in detail with special emphasis placed on the determination of interface states. No interface states with energies within the GaAs forbidden gap are found. The densities of states per layer are calculated and compared with bulk densities of states. They resemble the bulk densities of states except for layers adjacent to the interface

Carrier lifetimes in ion-damaged GaAs

Photoluminescence excitation correlation spectroscopy has been used to measure the dependence of carrier lifetime on the H+ ion implantation dose in GaAs. For doses greater than 1×10^12 cm^−2 the carrier lifetime is inversely proportional to the ion dose. The minimum lifetime measured was 0.6±0.2 ps for a dose of 1×10^14 cm^−2. Most important, there is no sign of saturation of carrier lifetime with ion dose down to this lifetime, thus still shorter lifetimes should be achievable with increased ion dose

Climate Change Crisis: Prescribing Alternative Economic Policy Using An Austrian Framework

This paper reviews the literature surrounding climate change adaptation and mitigation to assess the possible contributions and limitations of heterodox economics to climate change policy. Through interdisciplinary research between economics and environmental issues, this paper aims to stress the importance of utilizing heterodox schools of economics to create more pragmatic and dynamic policy. The secondary aim is to use Austrian frameworks to contribute to the construction of feasible, efficient, and equitable climate change policy. This paper used qualitative and textual analysis of the Austrian schools of economics conceptualize possible policy responses to climate change. Research found that the Austrian prescription of privatized climate change policy, though robust in internal validity, fallaciously believes in the power of property rights and tort litigation to feasibly, efficiently, and equitably resolve competing interests regarding the use of natural resources. Further research is needed to implicitly analyze the values hidden within adaptation and mitigation strategies. The limits and values of the social system dictate the limits and values that are carried over into economics and thus, climate change policy. It is necessary to understand and predict how economic systems, social systems, and institutions will evolve as economic stability, social cohesion, and institutional cooperation will affect the limits of climate change policy. Findings suggest that policy should abandon ‘either/or’ solutions in favor of ‘both/and’ solutions to climate change. This paper is useful in understanding environmental economics and institutional structures and evolution. The research provides further insight into heterodox perspectives of environmental economics

Pulsed laser deposition growth of Fe3O4 on III–V semiconductors for spin injection

We report on the growth of thin layers of Fe3O4 on GaAs and InAs by pulsed laser deposition. It is found that Fe3O4 grows epitaxially on InAs at a temperature of 350 °C. X-ray photoelecton spectroscopy (XPS) studies of the interface show little if any interface reaction resulting in a clean epitaxial interface. In contrast, Fe3O4 grows in columnar fashion on GaAs, oriented with respect to the growth direction but with random orientation in the plane of the substrate. In this case XPS analysis showed much more evidence of interface reactions, which may contribute to the random-in-plane growth

Who does what now? How physics lab instruction impacts student behaviors

While laboratory instruction is a cornerstone of physics education, the impact of student behaviours in labs on retention, persistence in the field, and the formation of students' physics identity remains an open question. In this study, we performed in-lab observations of student actions over two semesters in two pedagogically different sections of the same introductory physics course. We used a cluster analysis to identify different categories of student behaviour and analyzed how they correlate with lab structure and gender. We find that, in lab structures which fostered collaborative group work and promoted decision making, there was a task division along gender lines with respect to laptop and equipment usage (and found no such divide among students in guided verification labs).Comment: 4 pages, 3 figures, 3 table

Incremental submission of programming code using object-oriented classes

Given increasing adoption of agile software development methodologies it is essential that information technology students are exposed to them. This paper describes and evaluates an attempt to introduce agile programming into a core second year programming course. The initiative appeared to be associated with improvements in both drop out and pass rate, and student perceptions of the innovation were largely positive