功能材料雙語-電功能材料-wenkub
2023-01-27 15:39:43 本頁面
【正文】 es in the filled band， This process is known as electron–hole pair generation. The movement of electrons in the conduction band and holes in the filled band create current. types of semiconductor materials classified according to the position pure elements pounds solid solution 1. Elements conductor Elements conductor Intrinsic semiconductor 本征半導(dǎo)體 Extrinsic semiconductor 非本征半導(dǎo)體 pure semiconductor, no defect, the concentration of impurity is less than109 adding controlled impurities to a semiconductor to modify the conductivity ? the most mercially important of these elements are silicon （ 硅 ） and germanium （ 鍺 ） . Silicon and germanium are used here effectively because they have 4 valence electrons in their outermost shell which gives them the ability to gain or lose electrons equally at the same time. ? A pure semiconductor, however, is not very useful, as it is neither a very good insulator nor a very good conductor. ?Intrinsic semiconductor ?Extrinsic semiconductor(非本征半導(dǎo)體 /雜質(zhì)半導(dǎo)體 ) ? Adding impurity atoms （雜質(zhì)原子） to a semiconducting material, known as ―doping‖,（摻雜） greatly increases the number of charge carriers within it. Extrinsic semiconductor ntype ptype larger electron concentration than hole concentration， electrons are the majority carriers larger hole concentration than electron concentration, holes are the majority carriers ? Ntype semiconductor（ electron doners ） 電子施主 group VA（ N、 P、 As、 Sb、 Bi） introduced into group Ⅳ A of the periodic table （ C、 Si、 Ge、 Sn） , creates an extra free electron ? ptype semiconductor（ holes, acceptors ） 電子受主 group Ⅲ A（ B、 Al、 Ga、 In、 Ta） all contain three valence electrons, when used to dope group Ⅳ A （ C、 Si、 Ge、 Sn） ，a vacant state ( an electron hole) is created, which can move around the lattice and functions as a charge carrier ?Extrinsic semiconductor（非本征半導(dǎo)體） energy band of semiconductor ? ntype semiconductor: electron is in doner level 施 主 能 級(jí) , the energy difference between doner level and bottom of conduction band （ Ed） is much less than Eg（ about three orders of magnitude） , so electron can be more easily excited to the conduction band than intrinsic excitation本征激發(fā) ? for example: ? one over a billion of As doped Si， Eg is 1019 J， Ed is 1021 J. ? one over a billion of Sb doped Ge， Eg is 1019 J， Ed 1021 J. ? ptype semiconductor: hole is in accepted level受主能級(jí) , the energy difference between accepted level and top of conduction band （ Ea）is much less than Eg, so electron in valence band can be more easily excited to the accepted band and leave an hole in valence band. ?binary pound二元化合物
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