Mobile charge carrier density

In order to calculate diffusion coefficient, mobility and mobile charge carrier density of an electrolyte values of i2 and 8 should thus be obtained. There are actually many ways to estimate i2 and 5 using electrical and dielectric measurements. 

Finally, it can be concluded that the mobile charge carrier density of electrolytes can be... 

The excellent agreement between the TSC and P1A results has two implications. First, since the TSC method probes the product of mobility and carrier density, while the P1A probes only the carrier density, there seems to be no dominant influence of temperature on the carrier mobility. This was also found in other conjugated polymers like /ra/ry-polyacetylene [19, 36]. Second, photoconductivity (observed via the thermal release of photoexcited and trapped earners) and photo-induced absorption probe the same charged entity [36, 37J. 

On lowering the temperature through Ty, a bandgap Eg = 0.1 eV appears in the FeB-ai(l) conduction band of Fig. 3 at Ep. The Hall coefficient increases as Rh exp(Ty/T), indicating that the charge-carrier density increases exponentially with T" , as in a normal semiconductor, and the Hall mobility increases from about 0.1 to 0.4 cm /Vs on lowering the temperature from Ty = 120 K to 77 K ... 

The mobilities of holes are always less than those of electrons that is fXh < Me- In silicon and germanium, the ratio [ie/[ih is approximately three and two, respectively (see Table 6.2). Since the mobilities change only slightly as compared to the change of the charge carrier densities with temperature, the temperature variation of conductivity for an intrinsic semiconductor is similar to that of charge carrier density. 

Neglecting the variation of the term, which is negligible compared to the variation with temperature in the exponential term, and recalling that the mobilities are less sensitive to temperature than are the charge carrier densities, Eq. (6.30) can be rewritten as... 

Unlike intrinsic semiconductors, in which the conductivity is dominated by the exponential temperature aud band-gap expression of Eq. (6.31), the conductivity of extrinsic semiconductors is governed by competing forces charge carrier density and charge carrier mobility. At low temperatures, the number of charge carriers initially... 

In metals, the concentration of mobile electrons is enormously high so that the excess charge is confined to a region very close to the surface, within atomic distances [14, 15]. In semiconductors with substantially less charge carrier density, on the other hand, a region of spatial charge distribution can be found [16, 17]. 

If an electric field is applied to the surface of the semiconductor from whatever source, the density of the mobile charge carriers (holes) is either enhanced or depleted, depending on the polarity of the field. If the field enhances the concentration of holes, the surface is said to be accumulated and the semiconductor surface behaves much as a metal, in that the excess charge appears at the surface and the electric field does not penetrate it further. 

The surface field effect can be realized in a number of ways. The semiconductor can be built into a capacitor and an external potential applied (IGFET), or the field can arise from the chemical effects on the gate materials (CHEMFET). In both cases, change in the surface electric field intensity changes the density of mobile charge carriers in the surface inversion layer. The physical effect that is measured is the change in the electric current carried by the surface inversion layer, called the drain current. 

If a material containing a density, n, of mobile charge carriers, each carrying a charge Q, is situated in an electric field E, the charge carriers experience a force... 

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