Effects Of Channel Thickness Research Articles

A simulation study on the effect of channel thickness on the characteristics of Ga0.52In0.48P/In0.2Ga0.8As/Ga0.52In0.48P DH-pHEMT

The dc performance of a Ga0.52In0.48P/In0.2Ga0.8As/Ga0.52In0.48P double heterojunction pseudomorphic high electron mobility transistor (DH-pHEMT) grown on GaAs substrate has been simulated using a two-dimensional device simulator, to investigate the dependence of the intrinsic and extrinsic transconductance on the device channel thickness. The electron sheet concentration values for different channel thicknesses have been calculated using an analytical model, and correspond very well to Hall effect measurements of the electron mobility. Simulation results reveal that the optimum channel thickness for maximum intrinsic transconductance is between 80 and 100Å, while there is no significant difference in the maximum extrinsic transconductance for channel thicknesses between 80 and 140Å. This is due to a trade-off between electron sheet concentration and gate-to-channel separation. In addition, narrow channels give larger effective band gap due to energy quantization, which could contribute to an optimum design for Ga0.52In0.48P/In0.2Ga0.8As/Ga0.52In0.48P DH-pHEMTs.

Effect of channel thickness on linearity of doublepulse doped AlInAs/GaInAs/InP HEMTs

The effect of channel thickness on device characteristics was explored using double pulse doped AlInAs/GaInAs/InP HEMTs. On-wafer RF characterisation results revealed that the transconductance variation with gate voltage can be significantly minimised by increasing the channel thickness. However, a tradeoff between linearity and peak unity current gain cutoff frequency exists as a result of increased average separation between the gate and the 2D electron gas.

Effect of Channelling in a Porous Medium on Radionuclide Migration

ABSTRACTA mathematical model has been developed to study the effect of channelling in a porous medium surrounding a repository on the migration of radionuclides. The porous medium is treated as an infinite medium containing parallel, unconnected channels; each channel is surrounded by a rock matrix. The migration in the channel is controlled by convection and diffusion processes in the direction of the flow, whereas in the rock matrix it is dominated by anisotropic diffusion in the longitudinal and transverse directions. Unsteady state convective-diffusion equations for this system have been solved. At the channel-rock matrix interface the concentration and flux were watched to obtain concentration profiles and discharge rates at downstream locations. By means of a parametric study the effects of channel thickness, diffusion coefficients, and flow velocity on the migration rate are elucidated.