Density of trapped charges

As stated earlier, we have made use of the fact that the Fermi level Ep is shifted towards the band edge E from the value at zero gate bias by an amount qV (see Figure 2.2.9). is the density of trapped charge at zero gate... 

Support for the applicability of this model to an explanation of the Meyer-Neldel rule comes from measurements of space-charge limited currents in anthracene where a correlation (see Fig. 20) has been found between the total density of traps H and the distribution parameter Tc (Owen et al, 1974). It has been shown that this effect is not fortuitous as suggested by some workers... 

Fig. 9.21. Density of slow charge trapping states at an interface of a-Si H with a-SijN., H when there is a thin graded-composition layer at the interface (Street and Tsai 1986).

DIFFERENCES IN THE distribution of charges between a metal and a semiconductor electrode surface are considered. Using a simplified model the densities of the charge carriers in a semiconductor electrode can be calculated. Calculated results are in agreement with differential capacity measurements in germanium electrodes. The influence of current through the electrode surface and of the formation of surface traps is considered. 

Such an observation of strong VG and T dependent EA can be explained using the multi trap and release model which assumes a semiconductor with Fermi level closer to the band edge and upon applying VG the Fermi level moves through the distribution of band tail states. As a result EA is reduced as the density of injected charge carriers are increased above the mobility edge [4, 6-11],... 

In the context of the multiple trapping and release (MTR) model, the decrease in transistor current upon introduction of vapor results from an increase in the density of traps due to the electrostatic properties of the analyte molecules, which introduce additional trap states in the material. As a result, the ratio of mobile charges to total charges decreases, causing a decrease in the measured mobility. Physically, the analyte molecule acts as an electrostatic... 

Fig. 17. Diagram in

In the presence of traps, the injected charge separates into a distribution with a density Uj of trapped charges and n of free charges. The two distributions together determine the internal field F(x), according to the Poisson equation... 

In these equations, n is the density of the free charge carriers, ( the density of the charge carriers captured in shallow traps, s the static dielectric constant, the density of states at the transport level Eg, Vext the applied voltage, and G(( ) gives the density of the trapping states per energy interval dE. Ne in disordered fUms or in crystals with narrow conduction bands is equal to the number of molecules per unit volume. 

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