Compound semiconductors electron mobility

Bipolarons are mobile electron pairs. They have been identified in a small temperature interval above the semiconductor-metal transition in Ti407 In this case, they represent mobile electron-pair bonds in a mixed-valence compound, the electrons condensing into metal-metal homopolar bonds that are ordered at low temperatures, but become disordered and mobile at somewhat higher temperatures. 

The specific application of a material generally determines the particular structure desired. For example, hydrogenated amorphous silicon is used for solar cells and some specialized electronic devices (10). Because of their higher carrier mobility (see Carrier Transport, Generation, and Recombination), single-crystalline elemental or compound semiconductors are used in the majority of electronic devices. Polycrystalline metal films and highly doped polycrystalline films of silicon are used for conductors and resistors in device applications. 

The most dramatic example of the use of functionalization to tune the properties of an organic semiconductor is found in perfluoropentacene 41 (Scheme 3.9) [53]. Perfluoropentacene has a strongly shifted LUMO, evidenced by lowering of the reduction potential by more than 700 mV. The fluorinated compound adopts a herringbone packing in the crystal that is very similar to that of the parent acene. Top-contact FET devices made from evaporated 41 had an electron mobility of 0.11 cm2 V-1 s 1, demonstrating the change from p-type to n-type behavior. 

While a lot of work has been very recently devoted to oUgothiophene-based n-type organic semiconductors [355,378-381], the number of n-type PT-based organic semiconductors remains very limited [ 103382,383]. Polymer 209 and its model compound 210 [384] are sohition-processable organic semiconductors that enable the realization of OTFTs by solution-casting. While compound 210 exhibits a high-electron mobility (p. ) of 0.25 cm s the mobility of polymer 209 remains weak (p = 10 cm s ). 

Table tr.1-20 Electron mobilities /Xn and hole mobilities /Xp of Group IV semiconductors and IV-IV compounds... 

The early work of Erode on compound semiconductor TFTs led to the eurrent active matrices based on silicon TFTs. A low-temperature process utilizes amorphous sihcon films (a-Si H) as the semiconduetor, while higher-temperature versions are based on better performing polycrystaUine siheon films (poly-Si). Table 7.5 compares the various approaches and gives an example of glass needed for use with each. Electronic mobility may be taken as a figure of merit for TFT performance, the higher the better. 

Since the benzothiadiazole units are often found in p-type/ambipolar semiconductors as described above, additional electron-accepting units are required to achieve n-type-dominated behavior. Introduction of the benzothiadiazole units in n-type semiconductors is advantageous to acquire low-lying LUMO levels and enhance intermolecular interactions through heteroatom contacts. The perfluo-roalkylated compound 81c showed an electron mobility of 4.7 x 10 cm s ... 

Indium antimonide inorg chem InSb Crystals that melt at 535°C an intermetallic compound having semiconductor properties and the highest room-temperature electron mobility of any known material used in Hall-effect and magnetoresistive devices and as an infrared detector, j in-ds-cm, an tim-3,nTd ... 

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