Electron hole mobility

Recently, the effects of static and dynamic structural fluctuations on the electron hole mobility in DNA were studied using a time-dependent self-consistent field method [33]. The motion of holes was coupled to fluctuations of two step parameters of a duplex, rise and twist (Fig. 1), namely the distances and the dihedral angles between base pairs, respectively. The hole mobility in an ideally ordered poly(G)-poly(C) duplex was found to be decreased by two orders of magnitude due to twisting of base pairs and static energy disorder. A hole mobility of 0.1 cm V s was predicted for a homogeneous system the mobility of natural duplexes is expected to be much lower [33]. In this context, one can mention several theoretical studies, based on band structure approaches, to estimate the electrical conductivity of DNA [85-87]. 

Similar investigations have been carried out for the system LaCr xMnx03 [106]. A significant improvement in sinterability appears when Mn is substituted for Cr. For example, densities above 95% of theoretical were achieved at 1475 °C in air for La0.9Sr0 ]Cr03Mn07O3. Electrical conductivity and Seebeck coefficient results are interpreted by a small polaron mechanism for all compositions. This is illustrated for conductivity in Fig. 33. It was also demonstrated that the carrier (electron hole) mobility rather than carrier concentration governs the electronic transport. 

Figure 13-12. The recombination profiles for an OLED with an ohmic anode and an injection-limited cathode for various ratios of the electron/hole mobilities. Reproduced with permission from [145],...

Thus, one will use some materials referred to as electron/hole transport layer (ETL/ HTL), which will be designed to exhibit a high electron/hole mobility, and accordingly electroluminescent material (EML), and electron/hole injection layer (EIL/HIL). 

Since in the system investigated only the linear velocity changes, all other variables and constants are lumped together in K. Assuming now that the electronic conductivity of the scale is the limiting factor rather than the ionic one, the cathodic current can be set to be proportional to the electron hole concentration times the electron hole mobility ... 

Indium phosphide has an electron/hole mobility ratio of 40 1 which is considerably greater than that of either GaAs or Si. It is more suitable than the last two for higher-frequency operation. Indium... 

Electron, hole mobility fi// Hall mobility of charge carriers... 

Electron hole (p-type) conductivity has been observed in ceria at p02 1-400 atm in the temperature range 600-1100 °C. Electron holes were envisaged to arise according to reaction (12.16), where the vacancies are induced by lower valent impurities or by formation of cation vacancies having an effective negative charge V. A pOs exponent of 1/4 was observed at 700°C and pO2 400 atm. An electron hole mobility of approximately 10 cm V s was estimated at 800 °C, significantly lower than the electron mobility of about 6.1 X 10 cm V s at the same temperature. ... 

Electrical conductivity for an intrinsic semiconductor-dependence on electron/hole concentrations and electron/hole mobilities... 

Cryoelectronics. Operation of CMOS devices at lower temperatures offers several advantages and some disadvantages (53). Operation at Hquid nitrogen temperatures (77 K) has been shown to double the performance of CMOS logic circuits (54). In part, this is the result of the increase in electron and hole mobilities with lower temperatures. The mobiHty decreases at high fields as carrier speeds approach saturation. Velocity saturation is more important for cryoelectronics because saturation velocities increase by only 25% at 77 K but saturation occurs at much lower fields. Although speedup can... 

The relatively high mobilities of conducting electrons and electron holes contribute appreciably to electrical conductivity. In some cases, metallic levels of conductivity result ia others, the electronic contribution is extremely small. In all cases the electrical conductivity can be iaterpreted ia terms of carrier concentration and carrier mobiUties. Including all modes of conduction, the electronic and ionic conductivity is given by the general equation ... 

Studies of double carrier injection and transport in insulators and semiconductors (the so called bipolar current problem) date all the way back to the 1950s. A solution that relates to the operation of OLEDs was provided recently by Scott et al. [142], who extended the work of Parmenter and Ruppel [143] to include Lange-vin recombination. In order to obtain an analytic solution, diffusion was ignored and the electron and hole mobilities were taken to be electric field-independent. The current-voltage relation was derived and expressed in terms of two independent boundary conditions, the relative electron contributions to the current at the anode, jJfVj, and at the cathode, JKplJ. 

Figure 13-14. Spatial profiles of the carrier densities and the recombination for devices of width 100 nrn (dotted lilies) and 10 pm (solid lilies), for equal electron and hole mobilities. Reproduced with permission from I05J. Copyright I99K by the American Physical Society.

The high electrical conductivity of metals as well as the high electron (and hole) mobility of inorganic covalently bound semiconductors have both been clarified by the band theory [I9, which slates that the discrele energy levels of individual atoms widen in the solid stale into alternatively allowed and forbidden bands. The... 

Using this model they have tried to look at important chemical processes at metal surfaces to deduce the role of electronic nonadiabaticity. In particular, they have tried to evaluate the importance of electron-hole-pair excitation in scattering, sticking and surface mobility of CO on a Cu(100) surface.36,37 Those studies indicated that the magnitude of energy transferred by coupling to the electron bath was significantly less than that coupled to phonons. Thus the role of electron-hole-pair excitation in... 

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