Mobility extraction

Data for step-mobilities shown in Fig. 6 span an impressively large range a factor of 10 " separates step-mobilities measured by STM from the step-mobilities extracted from the relaxation of micron-sized gratings. Some discrepancies exist, but most of the step-mobilities are consistent with a single activation energy of 1.8 eV and an attempt rate given by the frequency of atomic vibrations. We hope that this initial comparison of step-mobility data will help motivate more detailed theoretical analysis and experiments on the coimections between step-mobility and the evolution of surface morphology. 

Figure 5.11 Effective channel mobility extracted from a 100 m/100lateral 4H-SiC FET with a buried channel structure. (After [29].)...

It was found that 368 exhibits ambipolar activity with appreciable electron (0.12 cm2 V 1 s ) and hole (0.008 cm2 V 1 s-1) mobilities at the substrate growth temperature of 70°C, and 371 shows monopolar n-type activity with a high mobility of 0.32 cm2 V-1 s-1 for semiconducting films deposited at a substrate temperature of 25°C. 373 exhibits stable n-type activity even in the air although the observed electron mobility in the air (0.01 cm2 V-1 s ) is somewhat lower than that under vacuum (0.08 cm2 V-1 s-1). In the case of 368 films grown at 70°C, both n- and p-type mobilities as well as current on-off ratios are enhanced by orders of magnitude compared to films grown at 25°C. 369 exhibits only p-type activity, with no detectable n-type behavior. Hole mobility extracted from the transfer plot is 5 x 10-14 cm2 V-1 s 1 with... 

Fig. 14.4. I mpression of the uniformity of a QVGA active-matrix backplane based on measurements of 380 pixel TFT. (a) Distribution of the mobility, extracted from the...

In practice, a-Si H FETs are nevertheless frequently characterized by means of an effective-field drift mobility, extracted by fitting classical IGFET theory to a a limited range of device performance (this approach is also used in the preceding chapter). The justification for such an approach is that it greatly facilitates a comparison with conventional devices. 

We have focused on the mobility as the main parameter characterizing charge transport. The photocurrent transients, however, typically extend well past the nominal transit time (ft), so that the nominal mobility extracted from ft underestimates the time required for charge to be transported across a photoreceptor film. A proper characterization of a material, therefore, requires some quantity indicating the width of the tail relative to ft [72a], As discussed previously, the tail is believed to arise because individual carriers sample various numbers of slow sites ,... 

FIGURE 2.1.20 Upper panel the temperature dependences of the Hall mobility, (solid circles) and the effective mobility, extracted from the conventional FET equations — that is, from the longitudinal FET conductivity and the density of charges, n, field induced above the threshold (Equation 2.1.2) (open circles). Lower panel the temperature dependence of the ratio of the Hall carrier density, %, to the density n. (From Podzorov, V. et al., Phys. Rev. Lett., 95, 226601, 2005.)... 

For small values of Vds, Q x) is approximately constant because the field across the Vqs and Vqd interfaces are similar. The carrier velocity, Elateral(x), is therefore constant. As the device begins to pinch off, Q becomes a stronger function of x, and the carrier velocity and lateral field are no longer constant across the length of the channel. In this case this method of mobility extraction is not valid. 

Solute permeation from the donor feed to the receiving strip phases across a LM can be mediated by a mobile extractant (carrier), resulting in the so-eaUed facUitated transport, or simply due to a different solubility of the solutes in the above mentioned two phases, resulting in the so-called non-facilitated transport. 

The field effect mobility may also be decreased by interface states. This is supported by the increase of the field effect mobility by using different insulators [250, 350]. Also drift mobilities extracted from electroluminescence measurements show a thickness dependence pointing to an influence of the interface [351],... 

Equations (4) and (5) are the premise for the most popular methods for mobility extraction. The probably most widespread one makes use of the transfer characteristic in the saturation regime. More precisely, the square root of the drain current is plotted as a function of the gate voltage. The principle of the method can be illustrated by rewriting Eq. (5) as... 

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