Hall scattering factor

Hall effect is the most widely used technique to measure the transport properties and assess the quality of epitaxial layers. For semiconductor materials, it yields the carrier concentration, its type, and carrier mobility. More specifically, experimental data on Hall measurements over a wide temperature range (4.2-300 K) provide quantitative information on impurities, imperfections, uniformity, scattering mechanisms, and so on. The Hall coefficient and resistivity (p) are experimentally determined and then related to the electrical parameters through (for n-type conduction) ffn = fulne and M-h = f n/P. where n is the free electron concentration, e is the unit electronic charge, Ph is the Hall mobility, and Th is the Hall scattering factor that depends on the particular scattering mechanism. The drift mobility is the average velocity per unit electric field in the limit of zero electric field and is related to the Hall mobility... 

It is evident from Table 1 that the Hall coefficient R and the electrical conductivity or, measured at 1.7 K, were the highest for samples 1-3. These samples were characterized also by the largest values of the characteristic temperatures. An analysis of the atomic scattering factors fiig of samples 5 and 6 indicated that they were 0.44% smaller than the factors / g for samples 1-3. This indicated that samples 5 and 6 were not stoichiometric but deficient in mercury. The lattice period was the same for all the samples and equal to 6.4590 0.0005 A. The constancy of the lattice period could be explained by the superposition of two effects. The formation of vacancies at the expense of the component with the larger atomic radius reduced the lattice period but the weakening of the atomic binding forces compensated this reduction. This was confirmed by a decrease in the characteristic temperatures of samples 5 and 6. 

Hall and drift mobilities have been measured in mixtures of n-pentane and NP by Itoh et al., (1991) between 20 and 150°C. They found both mobilities to decrease with the addition of n-pentane to the extent that the Hall mobility in a 30% solution was reduced by a factor of about 5 relative to pure NR However the Hall ratio remained in the range 0.9 to 1.5. This indicates that, up to 30% n-pentane solution in NP, the incipient traps are not strong enough to bind an electron permanently. However, they are effective in providing additional scattering mechanism for electrons in the conducting state. 

Equations 1-4 can easily be set up on a PC and used to simulate or fit temperature-dependent mobility data. In an n-type sample, the only undetermined parameter is the acceptor concentration Na, so usually Na is varied to give the best fit to the data. (For this fit, the approximate carrier concentration, nn = 1/Re, can be used when n is required in the various scattering formulas.) Then, the Hall factor r = can be calculated at... 

Because of the scattering in the visible portion of the spectrum, any extinction due to colloidal Pb would be masked and consequently it has not been possible to date to observe the tpyical colloidal extinction due to irradiation as observed in single crystals [7, 8, 59]. However, Garrett [85] has found that the quantum efficiency for N2 evolution from single crystals is within a factor of approximately two of that reported by Hall and Williams [96] for films for 330 nm irradiation. While the wavelength dependence of the quantum efficiencies for... 

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