Mobility, intrinsic charge carrier

Figure 22.12 Intrinsic charge carrier mobilities of DHnT as a dependence on the channel length for sub-micrometer devices.

Semiconductors for practical applications are often doped, mainly with the aim to improve the conductivity. In metal oxide photoelectrodes, shallow donors and acceptors are almost always necessary because of the low intrinsic charge carrier mobilities. The conductivity of the material is given by a = nefif, + so... 

Unlike intrinsic semiconductors, in which the conductivity is dominated by the exponential temperature aud band-gap expression of Eq. (6.31), the conductivity of extrinsic semiconductors is governed by competing forces charge carrier density and charge carrier mobility. At low temperatures, the number of charge carriers initially... 

Stationary dark currents in disordered thin films which contain no intrinsic charge carriers require the injection of charge carriers. If Ohmic contacts have been prepared, then the stationary dark current is not limited by the contact resistance, but instead by the mobility and the injected space charge. Since about 1985, stationary dark currents through disordered thin films have attracted great interest, especially since at that time, suitable contacting methods were developed to permit injection of both electrons from the one electrode as well as holes from the other. This made... 

An intrinsic semiconductor is characterized by a small band gap and a low density of highly mobile intrinsic charge carriers. Electrons as well as holes contribute to the conductivity which increases with temperature. Phthalo-cyanine radicals such as the sandwich type PC2LU or PcLi carry intrinsic charges. Their facile oxidation and reduction suggests that intrinsic conductivity should be possible. The electrical properties of these materials, especially as thin films incorporated in various devices, have been studied [32]. 

In the preceding chapters we have looked at temperature dependencies of concentrations of electronic defects and point defects, and we have looked at the conductivity and mobility of thermally activated diffusing species. In the following we consider the charge carrier mobilities of electrons and holes in some more detail. For instance for an intrinsic electronic semiconductor (where n=p) we can from Eq. 6.29 in combination with Eqs. 6.23 and 6.24 write an expression for... 

To determine the conductivity contribution from intrinsic charge carriers at 300 K the carrier concentration of lO"" cm" has to be multiplied by the elementary charge and the mobility, which is found around 10 cmV(V.s) in conjugated polymers [100]. This leads to a value of 1.6 x 10 - cm This value is in accordance with experiments by Chiu et al. [101], who deduced the conductivity of pure PPP to be less than 10 ... 

Poly(3-hexylthiophene) (P3fTr) and its derivatives are another class of n-conjugated polymeric semiconductors that have received wide interest due to their relatively facile processability and high charge-carrier mobilities. The electrical properties of these materials can be controlled by many factors such as their intrinsic chemistry, processing conditions, and... 

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