Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

High-speed InGaP/GaAs HBTs using a simple collector undercuttechnique to reduce base-collector capacitance

High-speed InGaP/GaAs HBTs were fabricated using a simple collector undercut (CU) technique to physically remove the collector material underneath the extrinsic base region by selective etching for reducing base-collector capacitance (C_BC). The best HBTs achieved a f_T of 80 GHz and a f_max (MSG/MAG) of 171 GHz. To our knowledge, this is the highest f_max (MSG/MAG) ever reported for the InGaP/GaAs HBTs. Compared to the HBTs without CUs, the CU HBTs showed a factor of 1.38 times improvement in the highest achievable f_max (MSG/MAG) due to the significant reduction of the C_BC     

Low-frequency noise characteristics of lattice-matched(x=0.53) and strained (x>0.53) In0.52Al0.48As/InxGa1-xAs HEMT's

Extensive bias-dependent and temperature-dependent low-frequency (LF) noise measurements were performed on lattice-matched and strained In_0.52Al_0.48As/In_xGa_1-x As(0.53<x<0.70) HEMTs. The input-noise voltage spectra density is insensitive to V_DS bias and shows a minimum at V_GS corresponding to the peak g_m condition. The corresponding output-noise voltage spectral density, which depends strongly on the gain of the devices, increases with V_DS. The input noise was rather insensitive to indium (In) content. Temperature-dependent low-frequency noise measurements on these devices reveal shallow traps with energies of 0.11, 0.15, and 0.18 eV for 60%, 65%, and 70% In HEMTs. Noise transition frequencies for these devices were on the order of 200-300 MHz and remain almost the same for different channel In content and V_DS bias     

Serum sialic acid and its relationship to various haematological parameters, including erythrocyte sedimentation rate

Policies regarding ambulance diversion are critical to ensuring that EMS providers are aware of appropriate patient destinations, even before patients enter the system. Field EMS personnel should never be requested to prolong transport time intervals to search for an available hospital at the potential expense of patients' conditions and the immediate availability of out-of-hospital emergency care for the community. The responsibility for providing efficient emergency care to the community rests with all those who contribute to EMS structures and processes. All EMS system participants, including hospitals, EMS providers, local and regional lead agencies, and medical oversight authorities, must work together to create comprehensive ambulance diversion policies that satisfactorily meet each other's needs, while maintaining the highest regard for the needs of EMS patients and the entire community.     

Tradeoff between 1/f noise and microwave performance in AlGaAs/GaAsheterojunction bipolar transistors

The 1/f noise characteristics and microwave gain of AlGaAs/GaAs heterojunction bipolar transistors (HBT's) have been investigated as a function of surface passivation ledge length. These measurements clearly demonstrate that the ledge length imposes a tradeoff between the 1/f noise and microwave power gain performance. Compared to a conventional unpassivated self-aligned HBT, HBT's with 0.4 and 1.1 μm ledge lengths improve the equivalent input base noise current spectral density at 100 Hz by as much as 2 dB and 6.5 dB, respectively; while degrading the maximum available gain at 18 GHz by 0.3 dB and 2.4 dB, respectively     

Passivation of ZnO TFTs

Abstract— The impact of passivation processes on ZnO thin‐film transistors is reported. In general, passivation processes result in back‐channel doping, which corresponds to shifts in threshold voltage and changes in subthreshold slope. It was determined that ALD‐based passivation results in considerably smaller undesirable shifts than those observed with plasma‐based processes. Two approaches, one a bulk doping with ammonia and the other a surface treatment with hydrogen peroxide, to further mitigate the detrimental effects of the passivation process are described. After proper passivation, ZnO devices show negligible hysteresis, have excellent stability to bias stress, and maintain or improve the good transport properties of as‐deposited devices. Although the existence of grain boundaries has been assumed to be a point of concern for device stability in polycrystalline metal oxides, no evidence was found to suggest that the grain boundaries present in these ZnO thin‐film transistors have affected the device stability.     

Enteropathy associated T cell lymphoma presenting as an isolated CNS lymphoma three years after diagnosis of coeliac disease: T cell receptor polymerase chain reaction studies failed to show the original enteropathy to be a clonal disorder

We have studied the effects of methohexitone and propofol with and without alfentanil on seizure duration and recovery in this observer-blinded, prospective, randomized, crossover study involving 24 patients undergoing electroconvulsive therapy (ECT). Each patient had four treatment sessions, and received the following four i.v. regimens in random order: methohexitone 0.75 mg kg-1, methohexitone 0.50 mg kg-1 and alfentanil 10 micrograms kg-1, propofol 0.75 mg kg-1, propofol 0.50 mg kg-1 and alfentanil 10 micrograms kg-1. Additional methohexitone or propofol was given as needed in 10-20-mg increments until loss of consciousness. Suxamethonium 1.0 mg kg-1 i.v. was given for muscular paralysis. Mean motor and EEG seizure durations were longer with methohexitone-alfentanil (44.7 (SD 15.0) and 70.5 (29.7) s) than with methohexitone (37.6 (12.6) and 52.6 (15.3) s) and similarly, seizures were longer with propofol-alfentanil (36.8 (15.2) and 54.5 (20.9) s) than with propofol alone (27.2 (11.9) and 39.2 (3.9) s). Seizures were longest with methohexitone-alfentanil and shortest with propofol. Recovery time was statistically shorter in patients receiving propofol compared with methohexitone-alfentanil and methohexitone alone. Alfentanil with a reduced dose of methohexitone or propofol provided unconsciousness and increased seizure duration in patients undergoing ECT. We conclude that the combination of methohexitone with alfentanil is a good regimen for ECT, especially for patients with short seizure duration.     

W-band monolithic oscillator using InAlAs/InGaAs HEMT

A W-band monolithic integrated oscillator circuit was designed and fabricated using submicron HEMT technology. The oscillation frequency was around 81 GHz and the power was -7 dBm at the chip level. This is the first report of an InAlAs/InGaAs monolithic oscillator operating at the W-band.<>     

Modelling and numerical analysis for wavy edge in printed source and drain electrodes of thin-film transistors

The wavy edge in printed narrow line electrodes is modelled by using a sequence of semi-ellipses and its effect on the electrical performance of a hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) when the wavy patterns exist in its printed source and drain (S/D) electrodes is analysed. Based on ATLAS 3D simulation, it is found that peak-to-peak magnitude of the S/D wavy edge had large, period had small, and phase shift between S/D wavy patterns had negligible effects on the TFT performance change. A transmission line method was used to explain the S/D wavy edge effect in terms of an increase of the effective channel length.     

A review of optical limiting mechanisms and devices using organics, fullerenes, semiconductors and other materials

We review nonlinear optical processes in various materials which can be utilized in passive optical limiting devices. Specifically, the mechanisms of reverse saturable absorption, two-photon and free-carrier absorption, nonlinear refraction and induced scattering are examined, and the implementation of these processes in optical limiting devices is discussed. The effectiveness of each approach depends on the specific application for the optical limiting device, and the advantages and limitations of each are addressed. Different materials, such as fullerenes, organometallics, carbon black suspensions, semiconductors and liquid crystals, all of which have been used in optical limiting devices, are discussed. In spite of the variety of nonlinearities, materials, and device configurations that have been used to implement passive optical limiters, no single device or combination of devices has yet been identified that will protect any given sensor from all potential optical threats.