8-doping process, doped semiconductor

Electric current is conducted either by these excited electrons in the conduction band or by holes remaining in place of excited electrons in the original valence energy band. These holes have a positive effective charge. If an electron from a neighbouring atom jumps over into a free site (hole), then this process is equivalent to movement of the hole in the opposite direction. In the valence band, the electric current is thus conducted by these positive charge carriers. Semiconductors are divided into intrinsic semiconductors, where electrons are thermally excited to the conduction band, and semiconductors with intentionally introduced impurities, called doped semiconductors, where the traces of impurities account for most of the conductivity. 

Shklovskii, B. L. and Efros, A. L. (1984) Electronic Processes in Doped Semiconductors. Springer-Verlag, Berlin. 

In recent years, the electronics industry has made increasing use of ion imptamaiion as a method of doping semiconductors. Since rhe number of ions implanted is determined hy the charge transferred to the substrate and Iheir depth distribution hy the incident energy, ion implantation has improved the controllability and reproducibility of certain semiconductor device processing operations. Also, ion implantation processes do not... 

Several examples have been reported recently of solution-processed multilayer electroluminescence devices incorporating semiconductor nanocrystals as the active recombination centers (16-18, 164). Recently, attention has also turned to hybrid electroluminescent devices involving transition metal-doped nanocrystals (104, 165-167). Although many challenges remain, including more specific exploitation of the dopants in many cases, the devices demonstrated to date represent a new direction in application of doped semiconductor nanocrystals made possible by the compatibility of these luminescent nanocrystals with solution processing methodologies. 

Cyclopentadienyl compounds have been thoroughly investigated as suitable precursors to rare earth doped semiconductors in MOCVD (metal-organic chemical vapor deposition) or MOVPE (metal-organic vapor phase epitaxy) processes [283]. The use of btsa complexes for the same purpose has appeared in the literature very recently [285]. Typical process conditions are shown in Scheme 14. It was found that the carbon contamination of the deposited metal is less in the btsa case. 

This process describes the scattering of free carriers by the screened Coulomb potential of charged impurities (dopants) or defects theoretically treated already in 1946 by Conwell [74,75], later by Shockley [10] and Brooks and Herring [76,77]. In 1969, Fistul gave an overview on heavily-doped semiconductors [78]. A comprehensive review of the different theories and a comparison to the experimental data of elemental and compound semiconductors was performed by Chattopadhyay and Queisser in 1980 [79]. For nondegenerate semiconductors the ionized impurity mobility is given by [79] ... 

For a doped semiconductor, the Fermi level position will be shifted from mid-gap, because the doping process will vary the tendency of the solid to either gain or lose electrons. For example, if donors are added to an intrinsic semicondnctor, the material will be more likely to lose electrons. The Fermi level of an n-type semiconductor will thus move closer to the vacuum level (i.e. will become more negative on the electrochemical potential scale) (Figure 9(b)). Similarly, if acceptors are added to an intrinsic material, the Fermi level will become more positive, because this phase will now have an increased tendency to accept electrons from another phase (Figure 9(c)). 

Gilman J. M. A., Batchelor R. A. and Hamnett A. (1993), Surface processes at electrolyte highly-doped semiconductor interfaces analysed by electroreflectance modelling , J. Chem. Soc. Earaday Trans. 89, 1717-1722. 

The process of semiconductor doping consists normally of two steps implantation of the dopant and annealing, to eliminate those defects created... 

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