Search Results - (Author, Cooperation:C. H. Yang)

2018-07-04

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-06-05

American Physical Society (APS)

1098-0121

1095-3795

Physics

Surface physics, nanoscale physics, low-dimensional systems

2015-10-06

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2018-03-07

The American Association of Immunologists (AAI)

0022-1767

1550-6606

Medicine

2018-10-31

Nature Publishing Group (NPG)

2041-1723

Biology

Chemistry and Pharmacology

Natural Sciences in General

Physics

2018-03-06

American Physical Society (APS)

0031-9007

1079-7114

Physics

Condensed Matter: Electronic Properties, etc.

1089-7550

AIP Digital Archive

Physics

To improve beam quality, an injection-seeded unstable resonator was applied to a discharge-pumped F2 laser, which is normally dominated by amplified spontaneous emission with a large beam divergence when using a normal stable cavity, due to the laser's extremely high gain (a small-signal gain-length product ∼29). The time-dependent injection-seeding efficiency was obtained for various injection timings by measuring a ratio of the output laser intensity with the same polarization as the seed laser. Correlation of the injection-seeding efficiency with the temporal evolution of the laser-beam divergence was also studied. Both the time-dependent beam divergence and the injection-seeding efficiency showed degradation at a later part of the laser pulse.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We report a calculation on the current-voltage characteristics of double-barrier resonant tunneling diodes. The results can well-explain experimental observations, in particular, the temperature dependence of both the absolute current amplitude and the resonant voltage positions. Our calculation takes into account the self-consistent Poisson equation, quantum mechanical tunneling, and band-gap offset at the heterojunctions. In addition, the calculation includes a realistic scattering-induced broadening effect, with which a quantitative fit throughout the entire negative differential resistance (NDR) region is demonstrated. Finally, we show that the differential resistance in the NDR region can be tuned, when asymmetrical tunneling barriers are used.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We have investigated magneto-transport and cyclotron resonance (CR) of two-dimensional electron gas in silicon δ-doped p-InSb under a magnetic field of up to 12 T at 4.2 K. Because there are multiple subbands occupied, Shubnikov–de Haas oscillations show a beating behavior. The CR spectra also display several peaks originating from different subbands. Effective masses of electrons associated with the lowest three subbands can therefore be directly determined, and they are in excellent agreement with a self-consistent calculation, which takes into account the electrostatic Poisson equation, the Schrödinger equation, and realistic sample parameters. Furthermore, we observed an absorption peak, whose resonance position has anomalous angle dependence. It is attributed to impurity CR where donors are in the vicinity of the δ-doped sheet.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We present quantum mechanical self-consistent calculations on the transfer characteristics of a new resonant tunneling transistor. The model structure consists of a source, a tunneling barrier, a quantum-well drain, a thick insulator, and a backgate. The tunneling barrier consists of a double-barrier structure. We demonstrate that based on energy and momentum conservations, the transistors display oscillatory negative transconductance, as the gate can control the resonant tunneling probability between source and drain. With the inclusion of a realistic energy relaxation time of ∼0.1 ps, the double-barrier resonant tunneling transistor shows an enhancement of the tunneling current density and the negative transconductance feature is only slightly changed. We also find that the quantum-well drain is not able to completely screen the electric field imposed by the backgate bias as a result of limited density of states of two-dimensional systems.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We investigated the current-voltage characteristics of double-barrier resonant tunneling diodes with areas ranged from ∼400 μm2 to ∼10 μm2 at a temperature of 300 and 4.2 K. For diodes of large areas, the characteristic negative differential resistance is always accompanied by a hysteresis and oscillation at several tens of MHz. However, for smaller diodes, the hysteresis and oscillation disappear, and the tunneling current shows a smooth transition between peak and valley. Our observation shows that the hysteresis can result from a load line effect. Were the hysteresis an intrinsic behavior, it should persist as the device area is reduced. We therefore conclude that the intrinsic bistability is yet to be experimentally confirmed.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We show that for narrow band-gap semiconductors, the doping concentration deduced from capacitance-voltage measurements can be substantially underestimated due to surface quantization effect. While our derivation can be applied to all materials, detailed accounts on p-type Hg0.788Cd0.212Te are given as an example. We found that for a practical doping range, 1×1015 cm−3 to 1×1017 cm−3, the doping level can be underestimated by 53% to 173%, respectively.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We report experimental observation on the area and temperature dependence of the hysteresis in the current-voltage characteristics of double-barrier resonant tunneling diodes. Our observation shows that the hysteresis can simply result from a load line effect, since (1) the hysteresis will disappear when the the device area is reduced, and (2) the hysteresis becomes wider at lower temperatures. We compare the data with theoretical predictions from the intrinsic bistability picture, and obtain the criterion for observing current bistability.

Electronic Resource

1365-2230

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

A 34-year-old woman presented with 2-year history of a dome-shaped papule on a well-circumscribed, thickened, port-wine stain on the left side of the chin. Squeezing on the port-wine-stain plaque revealed many comedos within dilated follicular orifices. The papule was excised and submitted for histological examination. Histopathological study showed a lobular neoplasm, comprising dilated, cystic pilosebaceous structures surrounded by fibrous stroma, bearing the characteristics of folliculosebaceous cystic hamartoma. The reported case shows that, in addition to the vascular nature, both ectodermal and mesenchymal abnormalities may be involved in port-wine stains.

Electronic Resource

1365-2133

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Docetaxel (Taxotere®), a semisynthetic taxoid, acts as an antimicrotubule agent and is considered to have great potential in the treatment of non-small cell lung cancer, advanced breast cancer, ovarian cancer and some other tumours. Well-recognized side-effects include dose-limiting neutropenia, fluid retention, myalgia, neuropathy, hypersensitivity reaction, alopecia, mucositis, nail changes and cutaneous reactions such as acral erythema. We describe a unique docetaxel-induced cutaneous reaction presenting as fixed erythematous plaque(s) unrelated to extravasation or previous skin injury; histopathological studies were performed in three of the four cases.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Theoretical analysis of the output performance of a transverse discharge pumped neon Penning laser (585.3 nm) using a mixture of Ne/H2 is described. The validity of the kinetic model is confirmed by comparing the results to the experimental discharge and laser performance. It is theoretically shown that the optimum mixing ratio of the Ne/H2 mixture is 1:2.5, and the optimum operating pressure is about 56 Torr. The model also predicts that the intrinsic efficiency reaches a peak of 8.5×10−6 at an excitation rate of 0.5 MW/cm3 under the optimum mixing ratio and operating pressure conditions. At excitation rates in excess of 0.5 MW/cm3 the laser output power is slowly increasing and then saturates due to electron collisional quenching of the upper laser level. The laser power extraction is increased by laser injection seeding in order to rapidly build up the lasing. The improved intrinsic efficiency is about two times higher than without the injection seeding. The improved specific laser output is 8 W/cm3, therefore, a discharge volume of 125 cm3 will be able to generate the peak laser power reaching 1 kW. This power value is sufficient to obtain the same treatment effect as the gold vapor laser used in photodynamic therapy. Moreover, by fitting this model to the experimental results of the laser output energy with a Ne/D2 mixture, it is shown that the Penning ionization rate constant of H2 is larger than that of D2. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We have investigated the transport properties of a field-effect transistor (FET) with a composite quantum well, which consists of two adjacent semiconductor quantum wells, GaSb and InAs, sandwiched by AlSb barriers. This FET shows a novel V-shaped transfer characteristic, which is a direct result of the switching between electron and hole channels.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We have studied photoluminescence from GaAs/Al0.3Ga0.7 As modulation-doped single heterojunctions, using excitation sources from infrared to ultraviolet near-liquid-helium temperature. The spectra have a strong interface component, accompanied by bulk GaAs and AlGaAs band-gap luminescence. Using ultraviolet instead of infrared as the excitation, the interface signal is greatly enhanced relative to the bulk GaAs luminescence. The interface signal can be shifted to the higher energies when a semitransparent front gate is positively biased. Our observations indicate that the interface luminescence comes from the recombination of the two-dimensional electrons with holes trapped at or near the interface. The peaks and the shoulders in the interface spectra appear to correspond to subbands of the two-dimensional electron gas at the interface. Our results demonstrate the feasibility of doing spectroscopic studies on high-mobility electrons at single heterojunctions.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We present device characteristics of a field-effect, unipolar, resonant tunneling transistor. An oscillatory tunneling current in the transfer characteristics is observed for the first time. Our observation confirms a recent hypothesis that a mere three-to-two dimensional resonant tunneling can occur when scattering rate is less than the attempt frequency of tunneling electrons in the quantum well.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We demonstrate for the first time that ion implantation and implant activation annealing, combined with a heavily doped InGaAs surface layer, can be used to make nonalloying shallow ohmic contact to an n-type InGaAs (or GaAs) quantum well. Quantum Hall effect and Shubnikov–de Haas oscillations are clearly observed, which indicates that electrons in the quantum well remain two dimensional despite the post-implantation high-temperature annealing. This technique can be applied to devices that would need to make shallow ohmic contact to a thin (∼100 A(ring) or less) quantum well, where existing selective etching approaches fail to work.

Electronic Resource