Electron and 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... 

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... 

H.C.F. Martens, J.N. Huiberts, and H.B. Brom, Simultaneous measurement of electron and hole mobilities in polymer light-emitting diodes, Appl. Phys. Lett., 77 1852-1853, 2000. 

A representative example for the information extracted from a TRMC experiment is the work of Prins et al. [141] on the electron and hole dynamics on isolated chains of solution-processable poly(thienylenevinylene) (PTV) derivatives in dilute solution. The mobility of both electrons and holes as well as the kinetics of their bimolecular recombination have been monitored by a 34-GHz microwave field. It was found that at room temperature both electrons and holes have high intrachain mobilities of fi = 0.23 0.04 cm A s and = 0.38 0.02 cm / V s V The electrons become trapped at defects or impurities within 4 ps while no trapping was observed for holes. The essential results are (1) that the trap-free mobilities of electrons and holes are comparable and (2) that the intra-chain hole mobility in PTV is about three orders of magnitude larger than the macroscopic hole mobility measured in PTV devices [142]. This proves that the mobilities inferred from ToF and FET experiments are limited by inter-chain hopping, in addition to possible trapping events. It also confirms the notion that there is no reason why electron and hole mobilities should be principally different. The fact... 

Fig. 23 (a) Dependence of the hole mobility in a film of poly-spiro-bifluorene-co-benzothiazole (PSF-BT) as function of the time elapsed after charge carrier generation by a 130 fs laser pulse at different applied voltages. The horizontal lines represent the electron and hole mobilities inferred from ToF experiments, (b) Momentary mobility as a function of the averaged distance that a carrier travelled after a given time. The inset depicts the chemical structure of PSF-BT. From [154] with permission. Copyright (2009) by the American Institute of Physics... 

Person 1 Use the data to write a relationship for the intrinsic conductivity of this substance as a function of the electron and hole mobilities. 

Assuming that the mobilities are the same in both the intrinsic and extrinsic states, combine your information to solve for the electron and hole mobilities of this substance. Can you tell whether the substance is an n-type of p-type extrinsic semiconductor by looking at the data ... 

At room temperature, the temperature dependence of electron and hole mobilities for intrinsic germanium is found to be proportional to for temperature in degrees Kelvin. Thus, a more appropriate form of Eq. (6.31) is... 

As alloying results in decreasing both the electron and hole mobility and... 

Room-Temperature Energy Gap and Electron and Hole Mobilities for Some... 

Fig. 4 Temperature dependence of electron and hole mobilities for durene single crystals (after Burshtein and Williams, 1977)...

Figure 96 Temperature dependence of the charge carrier mobility in organic single crystals, (a) The electron mobility in a crystal grown from moderately purified perylene (see Ref. 28), and (b) the electron (/ ) and hole (// ) mobilities in synthetic ultrapurified anthracene crystals at an electric field E 2.3x10 V/cm directed along the crystallographic axes b (adapted from Ref. 436a).

Figure 97 Arrhenius plot of electron and hole mobilities in the crystallographic c direction of a well-purified anthracene crystal (a) and for a 4x 10 7mol tetracane-doped anthracene crystal (b). After Ref. 442. Copyright 1975 Wiley-VCH, with permission.

Ab initio and Monte-Carlo calculations. Attempts have appeared in pulse radiolysis to describe the dynamics of free electron production, recombination and solvation on a microscopic scale [31-34]. This requires the knowledge of a number of physical parameters solvated electron and free ion yields, electron and hole mobilities, slowing-down cross-sections, localization and solvation times, etc. The movement and fate of each reactant is examined step by step in a probabilistic way and final results are obtained by averaging a number of calculated individual scenarios. 

The drift mobility in this dispersive regime has an unusual electric field and thickness dependence. Fig. 3.13 shows the field dependence of the electron and hole mobility at different temperatures (Marshall et al. 1986, Nebel, Bauer, Gom and Lechner 1989). The electron drift... 

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