Thermal generation current

Although the reverse current of an ideal Schottky barrier is J, in practice there are other current soitfces. Imperfect contacts have a leakage current which generally increases exponentially with bias. Even with an ideal contact, there is a thermal generation current caused by the excitation of electrons and holes from bulk gap states to the band edges. This mechanism determines the Fermi energy position under deep depletion conditions. The current density is the product of the density of states and the excitation rate and is approximately. 

There is a larger thermal generation current when the voltage is first applied, because the equilibrium E. is above Ef Y>... 

The depletion charge in low defect density a-Si H is 7 x 10 C cm , AE is about 0.1 eV and the leakage current has a decay time constant of about 100 s. Thus the thermal generation current is estimated to be... 

The low voltage data in Fig. 10.5 are explained by the thermal generation current. As formulated above, has no voltage dependence. However, the generation current is reduced when the bias voltage is too small to deplete the sensor, because not all the electron-hole pairs are collected. This is indicated by region A in Fig. 

When the temperature of a solar cell rises, cell conversion efficiency decreases because the additional thermal energy increases the thermally generated minority (dark-drift) current. This increase in dark-drift current is balanced in the cell by lowering the built-in barrier potential, lU, to boost the majority diffusion current. The drop in F causes a decrease in and F. Therefore, a cell s output, ie, the product of F and decreases with increasing cell temperature. is less sensitive to temperature changes than F and actually increases with temperature. 

Gases, vapors, and fumes usually do not exhibit significant inertial effects. In addition, some fine dusts, 5 to 10 micrometers or less in diameter, will not exhibit significant inertial effects. These contaminants will be transported with the surrounding air motion such as thermal air current, motion of machinery, movement of operators, and/or other room air currents. In such cases, the exterior hood needs to generate an airflow pattern and capture velocity sufficient to control the motion of the contaminants. However, as the airflow pattern created around a suction opening is not effective over a large distance, it is very difficult to control contaminants emitted from a source located at a di,stance from the exhaust outlet. In such a case, a low-momentum airflow is supplied across the contaminant source and toward the exhaust hood. The... 

Dark current comes from the thermal excitation of electrons in the detector material - thermally generated electrons can not be distinguished from photoelectrons. 

Figure 4. Principle of the measurement of thermally stimulated current (a) when the sample is irradiated at —150°C photocarriers are generated and the traps are filled with the carriers (b) measurement of the thermally stimulated current...

This paper touches on the chemistry of coal gasification and liquefaction comments on the current status of conversion processes and the influence of coal properties on coal performance in such processes and examines the contributions which coal conversion could make towards attainment of Canadian energy self-sufficiency. Particular attention is directed to a possible role for the medium-btu gas in long-term supply of fuel gas to residential and industrial consumers to linkages between partial conversion and thermal generation of electric energy and to coproduction of certain petrochemicals, fuel gas and liquid hydrocarbons by carbon monoxide hydrogenation. 

The method of field-induced thermally stimulated current (FITSC) consists of measuring— according to a definite (usually linear) heating scheme—the currents generated by the buildup and release of a polarized state in a high-resistivity solid... 

In the previous section, we considered electron transfer processes involving only the majority carrier band. For semiconductors with lower band-gaps, either doped or intrinsic, both bands may be involved and we consider two current contributions arising from the two bands as shown in Fig. 41. In practice, it is found that the dominant contribution usually arises from only one of the two bands if the majority carrier band is involved, the treatment will reduce to that given above, but if the minority carrier band is the more significant, then the current may be limited by the rate of thermal generation and transport of the majority carriers to the surface. 

Thermally stimulated currents (TSC) have been used to probe the carrier generation mechanism in a dual-layer photoreceptor with an azo-pigment-based CGL and hydrazone-based CTL. It appears that this technique may be a useful tool in understanding the carrier generation process in organic photoreceptors [21]. 

---