8 半导体简介.pptVIP

Technical English * Introduction to Semiconductors New words conductor导体 insulator绝缘体 crystalline晶体的 valency化合价 bond结合 covalent共价的 DNA 脱氧核糖核酸 deoxyribonucleic acid * molecule 分子 solder焊料, 焊接 polymorphic form 多晶型物 atom 原子 intrinsic固有的, 本质的 doping (半导体)掺杂(质) dopant 掺杂物, 掺杂剂 minuscule极小的 hole 空穴 * 本节中用到的几种化学元素（物质）名称： germanium 锗 silicon硅 tin 锡 boron 硼 selenium 硒 arsenic 砷 tellurium 碲 antimony 锑 arsenide 砷化物 gallium镓 * Text part 1 Semiconductors are materials that exhibit properties that are between a metal and a non-metal. Their electrical properties are part way between a conductor and an insulator―thus they are called “semi-conductors”. (Actually they are much closer to insulators than conductors.) A number of materials have these properties: ? The crystalline forms of most elements of Group IV (valency 4) (silicon[1], germanium, tin). * ? Some forms of specific elements—boron (Group III), arsenic and antimony (Group V), selenium and tellurium (Group VI). ? Crystalline alloys of elements in Group III (valency 3) with elements of group V (valency 5). Gallium arsenide (a compound or alloy of gallium and arsenic) is a good example here. ? Some compounds of elements of Group VI with elements of Group II. * Probably the most versatile elements are those with four electrons in their outer shell (Group IV: carbon, silicon, germanium, tin, lead). Because of the fact that they can have four bonds to four other elements, covalent compounds of endless complexity can be formed. (Indeed DNA is a single carbon-based molecule.) All of these elements can exist in multiple physical forms. Carbon can take many forms such as graphite (a form a bit like a classical metal) which conducts electricity very well or diamond (a crystalline form) which is an insulator. * Almost anyone who has ever soldered an electrical connection knows the difference between a good soldered joint (where the metal solidifies in a polymorphic form) and a “dry joint” where the solder crystallizes.[2] Po