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La3Ga5SiO14 (LGS) has been designed and used successfully not only as an electro-optical (EO) Q-switch but also as the optically active crystal in an Nd:YAG (yttrium aluminum garnet) pulse-off laser cavity with two-rod birefringence compensation in this paper. A maximum average output power of 15.8 W with a pulse width of 21 ns was obtained at the maximum repetition rate of 1 kHz, and the dynamic–static ratio was 75%. Experimental results revealed that the spatial distribution of the laser intensity with the two LGS crystals inserted between two identical Nd:YAG rods was significantly better than the spatial distribution with no birefringence compensation or a KD ∗ P EO Q-switcher. [ABSTRACT FROM AUTHOR]

The spin-Hamiltonian parameters (g factors, [image omitted], [image omitted], and hyperfine structure constants, [image omitted], [image omitted]) for Yb3+ at the 12-fold coordinated Sr2+ site of tetragonal SrTiO3 crystal at T ≈ 2 and 50 K were calculated using the completed diagonalization (of the energy matrix) method (CDM). Differing from the conventional CDM, the Hamiltonian concerning the energy matrix in this CDM contains the Zeeman and hyperfine interaction terms and so the spin-Hamiltonian parameters can be calculated directly from CDM. The crystal parameters used in the energy matrix are calculated from the superposition model, in which the tetragonal distortions and hence the order parameters φ at both temperatures are applied. From the calculations, the spin-Hamiltonian parameters at both temperatures are explained reasonably and the signs of hyperfine structure constants for the 171Yb3+ and 173Yb3+ isotopes in SrTiO3 are suggested. The results are discussed. [ABSTRACT FROM AUTHOR]

The spin-Hamiltonian (SH) parameters (g factors, g¶ and g⊥, and hyperfine structure constants, 171A¶, 171A⊥, 173A¶ and 173A⊥) for Yb3+ ions in trigonally-distorted octahedral sites of Na3Sc2V3O12 garnet were calculated from a complete diagonalization (of energy matrix) method (CDM) concerning 4f13 ions in trigonal symmetry. In the method, the Zeeman and hyperfine interaction terms are added to the Hamiltonian in the conventional CDM and the crystal-field parameters are estimated from the empirical superposition model. From the calculations, these SH parameters are explained reasonably. The defect structure of Yb3+ impurity centres in Na3Sc2V3O12 garnet and the signs of 171Ai (i = ¶ or ⊥) and 173Ai are also suggested. The intrinsic parameters in the superposition model obtained in the studied system show that [image omitted] > [image omitted] > [image omitted]. This point is consistent with the intrinsic parameters obtained for many rare earth ion systems and can be regarded as suitable. [ABSTRACT FROM AUTHOR]

Good-quality metamorphic InP buffer layers have been successfully grown on GaAs substrates by metal-organic chemical vapor deposition. Characterization by atomic force microscope, transmission electron microscopy, high-resolution X-ray diffraction, and Hall measurements indicated that the layers are of high crystalline quality, good mobility, and excellent surface morphology. On this buffer, we demonstrated the first metamorphic InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with good material quality and device performance. Metamorphic DHBTs showed direct-current and radio-frequency characteristics that are comparable to those grown on lattice-matched InP substrates. [ABSTRACT FROM AUTHOR]

Hepatic sequestration of systemically administered adenoviral vectors reduces the number of viral particles available for delivery to other tissues. The biological basis of this phenomenon was investigated using a new in vivo technique which permitted imaging in real time. Recombinant adenovirus serotype 5 knob (Ad5K) was radiolabeled with the gamma-emitter 99mTc (half-life = 6 h). Scatchard analysis of the 99mTc-Ad5K showed specific, high-affinity binding to U293 cells (Kd = 1.4 ± 0.5 nM), demonstrating that the radiolabeling process had no effect on receptor binding. In vivo dynamic imaging with an Anger gamma camera revealed that the liver binding followed an exponential rise to maximum, with a measured 100% extraction efficiency. Initially, the liver binding capacity was 3.1 ± 0.4 μg Ad5K, equivalent to approximately 17000 Ad5K molecules per liver cell. Liver binding was blocked by preincubation of Ad5K with neutralizing anti-Ad5K antibody; a 50% reduction in liver uptake was demonstrated by imaging. Unlabeled Ad5K was more effective in blocking liver uptake of 99mTc-Ad5K, whereas irrelevant unlabeled Ad3K had no effect. Imaging data for the liver uptake studies were in agreement with biodistribution determined by removing and measuring tissues. These data demonstrated that in vivo imaging is a sensitive tool for measuring changes to liver tropism. Similar imaging techniques can be applied to adenovirus vectors to measure specific targeting for gene therapy. [ABSTRACT FROM AUTHOR]

Emitter-size effects (ESEs) are experimentally investigated in GaAsSb-based double heterojunction bipolar transis- tors (DHBTs) with a new InP:GaInP composite emitter. This letter reveals that both the extrinsic base surface recombination and the intrinsic space charge recombination directly under the emitter are effectively suppressed over a wide range of collector current densities by eliminating the type-H conduction band at the emitter-base heterojunction. The reduction of ESEs enables aggressive scaling and suggests that the GaInP/GaAsSb heterojunction could become a key enabling element for sub-100-nm terahertz bandwidth InP/GaAsSb DHBTs. [ABSTRACT FROM AUTHOR]

Type-II InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with a 15-nm base were fabricated by contact lithography: 0.73 × 11 μm² emitter devices feature fT = 384 GHz (fMAX = 262 GHz) and BVCEO = 6 V. This is the highest fT ever reported for InP/GaAsSb DHBTs, and an "all-technology" record fT × BVCEO product of 2304 GHz·V. This result is credited to the favorable scaling of InP/GaAsSb/InP DHBT breakdown voltages (BVCEO) in thin collector structures. [ABSTRACT FROM AUTHOR]

Type-II InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with a 15-nm base were fabricated by contact lithography: 0.73 × 11 μm² emitter devices feature fT = 384 GHz (fMAX = 262 GHz) and BVCEO = 6 V. This is the highest fT ever reported for InP/GaAsSb DHBTs, and an "all-technology" record fT × BVCEO product of 2304 GHz·V. This result is credited to the favorable scaling of InP/GaAsSb/InP DHBT breakdown voltages (BVCEO) in thin collector structures. [ABSTRACT FROM AUTHOR]

We report on the tradeoff between current gain β and the base sheet resistance RSH in metalorganic chemical vapor deposition-grown NpN InP/GaAs1-xSbx/InP double-heterojunction bipolar transistors (DHBTs) with heavy base carbon-doping levels resulting in hole concentrations NB ranging from 4×1019 to 12×1019 /cm3. In contrast to Ga0.47In0.53As and GaAs–based transistors, which both display gain variations proportional to 1/(NB×WB)2 due to Auger recombination at high doping levels, neutral base recombination in InP/GaAsSb/InP DHBTs is not limited by Auger processes, and the measured current gain is proportional to 1/(NB×WB). We show that GaAs1-xSbx base layers offer a growing lifetime advantage over Ga0.47In0.53As with increasing doping levels. Potential explanations for the observed suppression of Auger recombination in the InP–GaAsSb system are proposed. [ABSTRACT FROM AUTHOR]

In "type-II' NpN InP-GaAsSb--InP double heterostructure bipolar transistors (DHBTs), the p+ GaAsSb base conduction band edge lies ΔEc, above the InP collector conduction band: a small ballistic injection energy ΔEc is thus imparted to electrons as they are launched into the collector. The resulting high initial velocity should in principle reduce the collector signal delay time in comparison to the case where thermal electrons are accelerated by the collector electric field alone. In this letter, we extract the bias dependence of the average collector electron velocity in high-speed InP-GaAs0.62Sb0.38-InP DHBTs, and find a maximum average velocity reaching 4 × 107 cm/s across a 2000 A InP collector. This finding provides evidence of the performance advantage afforded by abrupt type-Il base/collector (B/C) junctions for collector transport when compared to other B/C junctions. [ABSTRACT FROM AUTHOR]