A New Method for InGaAs/InP Composite Channel HEMTs Simulation

A new method is used to simulate InGaAs/InP composite channel high electron mobility transistors （HEMTs）. By coupling the hydrodynamic model and the density gradient model, the electron density distribution in the channel in different electric fields is obtained. This method is faster and more robust than traditional meth- ods and should be applicable to other types of HEMTs simulations. A detailed study of the InGaAs/InP composite channel HEMTs is presented with the help of simulations.

A comparative study on radiation reliability of composite channel InP high electron mobility transistors

This paper proposes a reasonable radiation-resistant composite channel structure for In P HEMTs.The simulation results show that the composite channel structure has excellent electrical properties due to increased modulation doping efficiency and carrier confinement.Moreover,the direct current(DC)and radio frequency(RF)characteristics and their reliability between the single channel structure and the composite channel structure after 75-ke V proton irradiation are compared in detail.The results show that the composite channel structure has excellent radiation tolerance.Mechanism analysis demonstrates that the composite channel structure weakens the carrier removal effect.This phenomenon can account for the increase of native carrier and the decrease of defect capture rate.

Diffusion of a chemically active colloidal particle in composite channels

Diffusion of colloidal particles in microchannels has been extensively investigated,where the channel wall is either a no-slip or a slip-passive boundary.However,in the context of active fluids,driving boundary walls are ubiquitous and are expected to have a substantial effect on the particle dynamics.By mesoscale simulations,we study the diffusion of a chemically active colloidal particle in composite channels,which are constructed by alternately arranging the no-slip and diffusio-osmotic boundary walls.In this case,the chemical reaction catalyzed by the active colloidal particle creates a local chemical gradient along the channel wall,which drives a diffusio-osmotic flow parallel to the wall.We show that the diffusio-osmotic flow can significantly change the spatial distribution and diffusion dynamics of the colloidal particle in the composite channels.By modulating the surface properties of the channel wall,we can achieve different patterns of colloidal position distribution.The findings thus propose a novel possibility to manipulate colloidal diffusion in microfluidics,and highlight the importance of driving boundary walls in dynamics of colloidal particles in microchannels.

Trap analysis of composite 2D-3D channel in AlGaN/GaN/graded-AlGaN:Si/GaN:C multi-heterostructure at different temperatures

The graded AlGaN:Si back barrier can form the majority of three-dimensional electron gases(3DEGs)at the GaN/graded AlGaN:Si heterostructure and create a composite two-dimensional(2D)-three-dimensional(3D)channel in AlGaN/GaN/graded-AlGaN:Si/GaN:C heterostructure(DH:Si/C).Frequency-dependent capacitances and conductance are measured to investigate the characteristics of the multi-temperature trap states of in DH:Si/C and AlGaN/GaN/GaN:C heterostructure(SH:C).There are fast,medium,and slow trap states in DH:Si/C,while only medium trap states exist in SH:C.The time constant/trap density for medium trap state in SH:C heterostructure are(11μs-17.7μs)/(1.1×10^13 cm^-2·eV^-1-3.9×10^13 cm^-2·eV^-1)and(8.7μs-14.1μs)/(0.7×10^13 cm^-2·eV^-1-1.9×10^13 cm^-2·eV^-1)at 300 K and 500 K respectively.The time constant/trap density for fast,medium,and slow trap states in DH:Si/C heterostructure are(4.2μs-7.7μs)/(1.5×10^13 cm^-2·eV^-1-3.2×10^13 cm^-2·eV^-1),(6.8μs-11.8μs)/(0.8×10^13 cm^-2·eV^-1-2.8×10^13 cm^-2·eV^-1),(30.1μs-151μs)/(7.5×10^12 cm^-2·eV^-1-7.8×10^12 cm^-2·eV^-1)at 300 K and(3.5μs-6.5μs)/(0.9×10^13 cm^-2·eV^-1-1.8×10^13 cm^-2·eV^-1),(4.9μs-9.4μs)/(0.6×10^13 cm^-2·eV^-1-1.7×10^13 cm^-2·eV^-1),(20.6μs-61.9μs)/(3.2×10^12 cm^-2·eV^-1-3.5×10^12 cm^-2·eV^-1)at 500 K,respectively.The DH:Si/C structure can effectively reduce the density of medium trap states compared with SH:C structure.

Analytical analysis of inclined three-layered composite channel with cobalt ferrite nanoparticles and Hall current in Darcy medium

The present study explores the influence of electromagnetic effects on the flow of a nanofluid in a saturated permeable medium,confined between a clear viscous fluid in an inclined channel.The nanofluid consists of cobalt ferrite nanoparticles dispersed in ethylene glycol.The governing equations are derived considering Darcy's law for the permeable medium and Tiwari's model for fluids containing nano-sized particles.Additionally,radiation and dissipation effects are incorporated into the energy equation.The equations are transformed into dimensionless form and solved analytically using the perturbation technique.The results are analyzed through graphs and tables for different material parameters.The findings reveal that higher electric and magnetic strengths have a significant impact on the fluid velocity at the interface of the two fluids,resulting in reduced shear both at the clear fluid surface and the interface between them.This highlights the crucial role played by electric and magnetic strengths in modifying flow phenomena.Consequently,combining electric and magnetic strengths with nanofluids can be utilized to achieve desired qualities in multi-fluid flow and enhance heat transfer characteristics.

Fabrication of 80-nm T-gate high indium In_(0.7)Ga_(0.3)As/In_(0.6)Ga_(0.4)As composite channels mHEMT on GaAs substrate with simple technological process

An 80-nm gate length metamorphic high electron mobility transistor （mHEMT） on a GaAs substrate with high indium composite compound-channels Ino.7Ga0.aAs/Ino.6Gao.aAs and an optimized grade buffer scheme is presented. High 2-DEG Hall mobility values of 10200 cm2/（V.s） and a sheet density of 3.5 x 10^12 cm-2 at 300 K have been achieved. The device＇s T-shaped gate was made by utilizing a simple three layers electron beam resist, instead of employing a passivation layer for the T-share gate, which is beneficial to decreasing parasitic capacitance and parasitic resistance of the gate and simplifying the device manufacturing process. The ohmic contact resistance Rc is 0.2 n.mm when using the same metal system with the gate （Pt/Ti/Pt/Au）, which reduces the manufacturing cycle of the device. The mHEMT device demonstrates excellent DC and RF characteristics. The peak extrinsic transconductance of 1.1 S/mm and the maximum drain current density of 0.86 A/mm are obtained. The unity current gain cut-off frequency （fT） and the maximum oscillation frequency （fmax） are 246 and 301 GHz, respectively.

Performance analysis of a random ARQ initialized cooperative communication protocol in shadowed Nakagami-m wireless channel

In this paper, we develop and analyze an energy efficient ARQ （automatic repeat request） initialized transmit diversity protocol for cooperative communications.Medium access control （MAC） layer packet retransmission limit （similar to aShortRetryLimit or aLongRetryLimit [802.11-1997]） has been used as an actuator for transmit cooperative diversity initialization.We take the channel state information （CSI） as a function of retransmission tries and the number of retransmission tries is modeled as a random variable.Relays close to the source node are chosen for the transmit cooperation.Closed form expressions are obtained for symbol error rate （SER）, outage capacity and outage probability for the proposed scheme in shadowed fading channels.This cooperative scheme achieves lower signal-to-noise ratio （SNR）, stumpy outage probability, higher bandwidth, and transmit energy efficiencies for desired average symbol error rate （ASER） than the preceding ARQ based cooperative protocols.Finally, the results of computer simulations are included to demonstrate the efficacy of the proposed scheme and to verify the accuracy of the analytical expressions.

Characteristics and Formation Mechanism of Polygonal Faults in Qiongdongnan Basin, Northern South China Sea

Based on high-resolution 3D seismic data, we document the polygonal faults within the Miocene Meishan （梅山） Formation and Huangliu （黄流） Formation of the Qiongdongnan （琼东南） basin, northern South China Sea. Within the seismic section and time coherent slice, densely distributed extensional faults with small throw and polygonal shape were identified in map view. The orientation of the polygonal faults is almost isotropic, indicating a non-tectonic origin. The deformation is clearly layer-bounded, with horizontal extension of 11.2% to 16%, and 13.2% on average. The distribution of polygonal faults shows a negative correlation with that of gas chimneys. The development of polygonal faults may be triggered by over-pressure pore fluid which is restricted in the fine-grained sediments of bathyal facies when the sediments is compacted by the burden above. The polygonal faults developed to balance the volumetric contraction and restricted extension. The product of hydrocarbon in the Meishan Formation may have contributed to the development of the polygonal faults. In the study area, it was thought that the petroleum system of the Neogene post-rift sequence is disadvantageous because of poor migration pathway. However, the discovery of polygonal faults in the Miocene strata, which may play an important role on the fluid migration, may change this view. A new model of the petroleum system for the study area is proposed.