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Electrical characterization of the gate-drain diode of an AlGaN/GaN HFET structure is performed by measuring the capacitance and conductance as a function of frequency for gate voltages near the threshold voltage. The results show consistency between the other studies of the frequency dispersion of electrical characteristics in AlGaN/GaN HFET.

Reports on the observation of rotational slip as a mechanism for relieving strain in III-V heterostructures grown by molecular beam epitaxy. Impact of rotational slip on the epitaxial layer; Relationship between the strain and the critical layer thickness; Description of rotational slip on planes.

Presents a study which determined the relationship between the aluminum mole fraction and the angular separation of film and substrate maxima in double axis x-ray diffraction rocking curves for strained epitaxial Al[subx]Ga[sub1-x]As films on (110)- and (111)-oriented gallium arsenide substrates. Details of how the films were grown; Values of the strained lattice parameter of the aluminum arsenide films normal to the wafer; Discussion of results.

Reports a study regarding the well-width dependence of photoinduced intersubband absorption in gallium arsenic (GaAs)/aluminum GaAs multi quantum wells. Distinction of multi quantum wells from bulk semiconductors; Growth of the GaAs/AlGaAs samples.

We report a submicrometer, self-aligned recess gate technology for millimeter-wave InAs-channel heterostructure field effect transistors. The recess gate structure is obtained in an n+ -InAs-InAlAs double cap layer structure with a citric-acid-based etchant. From molecular-beam epitaxy-grown material functional devices with 1000-, 500-, and 200-nm gate length were fabricated. From all three device geometries we obtain drive currents of at least 500 mA/mm, gate leakage currents below 2 mA/mm, and RF-transconductance of 1 S/mm. For the 200-nm gate length device fT and fmax are 162 and 137 GHz, respectively. For the 500-nm gate length device fT and fmax are 89 and 140 GHz, respectively. We observe scaling limitations at 200-nm gate length, in particular a negative threshold voltage shift from -550 to -810 mV, increased kink-effect, and a high gate-to-drain capacitance of 0.5 pF/mm. The present limitations to device scaling are discussed. [ABSTRACT FROM AUTHOR]

Transactive response DNA-binding (TDP-43) protein is the dominant disease protein in amyotrophic lateral sclerosis (ALS) and a sub-group of frontotemporal lobar degeneration (FTLD-TDP). Identification of TARDBP mutations in familial ALS confirms a mechanistic link between misaccumulation of TDP-43 and neurodegeneration and provides an opportunity to study TDP-43 proteinopathies in human neurons generated from patient fibroblasts using induced pluripotent stem cells (iPSC). Here, we report the generation of iPSCs that carry the TDP-43 M337V mutation, and their differentiation into neurons and functional motor neurons. Mutant neurons had elevated levels of soluble and detergent- resistant TDP-43 protein, decreased survival in longitudinal studies, and increased vulnerability to antagonism of the phosphoinositide 3-kinase pathway. We conclude that expression of physiological levels of TDP-43 in human neurons is sufficient to reveal a mutation-specific cell autonomous phenotype and strongly supports this approach for the study of disease mechanisms and for drug screening., Molecular and Cellular Biology

Extraordinary magnetoresistance (EMR) devices have been fabricated and characterized at various magnetic fields, operating temperatures, and current excitations. These devices are comprised of nonmagnetic high mobility semiconductors and low resistance metallic contacts and shunts. The resistance of the device is modulated by magnetic fields due to the Lorentz force steering an electron current between the high resistance semiconductor and the low resistance metallic shunt. The EMR devices were tested between 300 K and 5 K in magnetic fields up to 2 T perpendicular to the 2DEG plane and excitation currents up to 100 μA. Magnetoresistance increases as temperature decreases, potentially indicating that EMR persists even as dimensions approach the electron mean free path. [ABSTRACT FROM AUTHOR]