Effect of Defect Bands on the Electrical Characteristics of Irradiated GaAs and
Proton bombarded p-Si and neutron irradiated n-GaAs have been studied by DLTS, current±voltage, and capacitance±voltage measurements in metal±semiconductor junctions. The junctions were prepared by evaporation of Al onto silicon and of gold onto GaAs. Both junctions exhibited defect bands after bombardment. The bombardment has shifted the Fermi-level pinning position, increased the ideality factor in both junctions, and also affected the temperature dependence of the ideality factor and that of the capacitance. The results show that the main effect of the radiation is the generation of laterally inhomogeneous defects near the semiconductor surface.
Effect of Defect Bands on the Electrical Characteristics of Irradiated GaAs and Si
Proton bombarded p-Si and neutron irradiated n-GaAs have been studied by DLTS, current–voltage, and capacitance–voltage measurements in metal–semiconductor junctions. The junctions were prepared by evaporation of Al onto silicon and of gold onto GaAs. Both junctions exhibited defect bands after bombardment. The bombardment has shifted the Fermi-level pinning position, increased the ideality factor in both junctions, and also affected the temperature dependence of the ideality factor and that of the capacitance. The results show that the main effect of the radiation is the generation of laterally inhomogeneous defects near the semiconductor surface.
Influence of pressure and fluidization velocity on the hydrodynamics of a fluidized bed containing horizontal tubes
Abstract An experimental investigation of the influence of horizontal tubes on the bubble behaviour and through-flow velocity of gas inside bubbles was carried out and the influence of pressure and fluidization velocity was studied. The visible bubble flow rate and the gas velocity through the bubbles were measured simultaneously in a pressurized fluidized bed, using capacitance and Pitot-static pressures probes respectively. Silica sand with a mean particle diameter of 0.7 mm was fluidized at pressures between 01. and 1.6 MPa, in a bed of 0.2 × 0.3 m cross-section. Six different horizontal tube configurations were used and comparisons were made with results obtained in the same bed operated without tubes. The results from the bed with tubes show that the influence of pressure and fluidization velocity is basically the same as in the bed without tubes; an increase in pressure and fluidization velocity increases the bubble activity. At low excess gas velocities, the influence of immersed tubes on the bubble behaviour is less pronounced than at high excess gas velocities. Measurements and visual observations show that a small tube pitch gives a more uniform distribution of the visible bubble flow over the bed cross-section. At a combination of high pressure, high excess gas velocity and a large tube pitch, a preferred bubble path was observed in the centre of the bed cross-section. The pressure probe measurements show that the through-flow velocity of gas inside the bubbles is in most cases higher when tubes are present in the bed. The through-flow velocity consistently decreases with increasing pressure in the bed without tubes. The tendency is largely the same at a low excess gas velocity when tubes are present, but at a high excess gas velocity the through-flow velocity first decreases and then increases as the pressure is increased.