Carrier profiles

Another technique consists of MC measurements during potential modulation. In this case the MC change is measured synchronously with the potential change at an electrode/electrolyte interface and recorded. To a first approximation this information is equivalent to a first derivative of the just-explained MC-potential curve. However, the signals obtained will depend on the frequency of modulation, since it will influence the charge carrier profiles in the space charge layer of the semiconductor. 

Figure 27. Minority charge carrier profiles near the semiconductor/electrolyte junction. calculated for a silicon interface at two different electrode potentials. Uf- -0.25 V and Uf= 5.0 V10 ((//= forward bias = t/ - Ufl>).

Since under normal depletion conditions, conductivity changes are dominated by majority carriers, and interfacial electron transfer can be neglected in the dark, the carrier profile can be found by solving Poisson s equation ... 

Cross-flow FFF (F1FFF) utilizes a second fluid flow to transport sample components across the channel thickness to the accumulation wall, and the position of individual species in the laminar carrier profile corresponds to their ordinary (Fick s) diffusion coefficient. As the particle size increases, the diffusion coefficient (decreases until it becomes a relatively insignificant transport process. For micron-size particles, the extent of protrusion into the channel becomes the decisive factor in determining the order of elution. 

As mentioned earlier the condition — x very large and can be taken to be infinity. With this condition the mathematics is greatly simplified [37]. Now the electric field and carrier profiles are given by,... 

Currents, Excess Carrier Profiles, and Quasi-Fermi Levels... 

In the expression for the excess carrier concentration at the boundary to the space charge layer, Ap(W), the recombination velocity at the back contact, S,b, is contained (see equations A8, A9 in [45].). The terms C, C, D, D and the prefactor A contain expressions that are independent of the variable x. They are given in Appendix 2.A. Figure 2.4 shows examples of excess minority carrier profiles for a back contact recombination velocity Srb of 10 cm s which is in the range of the thermal velocity [46] for a set of minority carrier diffusion lengths that range from poor bulk mate-... 

Figure 2.4 Light-induced excess minority carrier profiles for different diffusion lengths of n-Si ...

The efficiency of photoelectrochemical devices is based on effective charge transfer while suppressing surface recombination and corrosion. While the photocurrent is a direct measure of the irreversibly transferred electrons, it is not trivial to obtain a measure for the losses at surfaces due to recombination. As will be shown in Section 2.3.1, stationary microwave reflectivity is a method that measures the integral of the excess minority carrier profile. Such profiles are shown in Figures 2.3-2.6. The simultaneous recording of photocurrent and excess microwave reflectivity in an electrochemical cell allows the assessment of the relative contributions of kr and Sr for well-defined systems. These parameters are defined as follows ... 

For further analysis, in particular regarding the signal from the majority carriers in n-Si where the electron mobility is about three times larger than that of the holes, the excess carrier profiles are considered separately in the space charge region 0 < x < W) and in the neutral region x> W). 

The charge distribution for the semiconductor-electrolyte system is given by the excess minority carrier profile Ap(x) (2.40a) and the corresponding neutralizing majority carrier profile. The microwave signal due to the minority carriers, AR, is given by the excess carrier distribution throughout the sample ... 

Thus, the recorded signal corresponds to the integral of the excess minority carrier profile throughout the sample modulated by the relative carrier mobilities. This finding was the basis for the analysis of the charge transfer and surface recombination velocity profiles above (cf Figures 2.16 and 2.17). 

The impact of space charge regions on combined electronic and ionic transport was presented by Maier [17]. The space charge potential, A( ) = [( )(0) — ([)( )], where c )(0) is the potential at the interface and c )(°o) is the reference value in the bulk, determines the charge carrier profiles in the space charge layer. The equilibrium condition for species j is given by the constancy of the electrochemical potential ... 

Before the auction, THD asked for carrier profile information from the 192 applicants. Of these, 111 were invited to participate in the auction. They were selected on the basis of acceptable quality, promise of a favorable business relationship, and sufficient size. 

The eo-diffusion of As and B which had been implanted to doses of about lOl /cm, using energies which gave the same projected range, was investigated at 900 and lOOOC by measuring dopant and carrier profiles. A comparison of co-diffusion data, with the results which were obtained by the separate diffusion of each element, revealed anomalous effeets which could be explained by positing the formation of neutral donor-acceptor pairs. These complexes were mobile, with diffusivities that could be described by ... 

Maintaining an accurate and up-to-date carrier profile has always been important for a motor carrier. However, under the Comprehensive Safety Analysis (CSA) enforcement model it will be even more crucial to make sure the data the Federal Motor Carrier Safety Administration (FMCSA) has on your carrier is correct. If you have the incorrect number of trucks, the FMCSA will not normalize the data on your carrier accurately and you may be placed in a peer group that is not apples to apples to compare you against. 

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