• 作者： 郎棣
• 作者服務機構： 國立清華大學
• 中文摘要： 本報告以暸解量子介電質理論及其對半導合金之應用為主，量子介電質理論研究對象以二元四面型結構，而每一對原子有八個價電子之晶體為主。基於飛利浦之電離度新定義及一般化之兩帶模式，構成此量子介電質理論。此理論應用於解決化學鍵性質，能帶同隙，晶體結構，甚至能量階數值等問題極為有效。以最少數之假定及參數，上述諸問題均可經由平均能隙之分為二部與介電質常數及光學性質發生關聯。平均能隙所分成之二部其一為同極性(或共價)，另一為異極性(或電離)，分別與近磷距離及負電度差有關。此法準確度極高。
• 英文摘要： This report is mainly a review of the quantum dielectric theory andits application in solving the electronic problems of semiconducting alloys.The major interest of this theory is on the ABe-" crystals which includemost tetrahedrally coordinated semiconductors and some rocksalt-typecrystals. Based on Phillips definition on ionicity and the Van Vechtendielectric two-band model, a method is formulated by which one may solvethe problems like bond character, average energy gap, and even the energylevels at high symmetry points of the conduction and valence bands ofmost binary semiconducting alloys with tetrahedral coordination. Underthe least possible number of assumptions, the direct interband gap is made torelate to the optical and dielectric information through the splitting of thegap into a homopolar (or covalent) part and a heteropolar (or ionic) part,the former of which is a function of nearest-neighbor distance only andthe latter is directly related to the electronegativity difference of the con-stituent atoms. This method has been applied to 68 crystals previously andfound that with much fewer number of parameters one may obtain moreaccurate results than other methods including the most promising empiricalpseudopotential method.
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