Electronic Structure Of Metal Semiconductor Contacts

Interface and surface science have been important in the development of semicon ductor physics right from the beginning on. Modern device concepts are not only based on p-n junctions, which are interfaces between regions containing different types of dopants, but take advantage of the electronic properties of semiconductor insulator interfaces, heterojunctions between distinct semiconductors, and metal semiconductor contacts. The latter ones stood almost at the very beginning of semi conductor physics at the end of the last century. The rectifying properties of metal-semiconductor contacts were first described by Braun in 1874. A physically correct explanation of unilateral conduction, as this deviation from Ohm's law was called, could not be given at that time. A prerequisite was Wilson's quantum theory of electronic semi-conductors which he published in 1931. A few years later, in 1938, Schottky finally explained the rectification at metal-semiconductor contacts by a space-

VLSI Electronics Microstructure Science, Volume 13: Metal-Semiconductor Contacts and Devices presents the physics, technology, and applications of metal-semiconductor barriers in digital integrated circuits. The emphasis is placed on the interplay among the theory, processing, and characterization techniques in the development of practical metal-semiconductor contacts and devices. This volume contains chapters that are devoted to the discussion of the physics of metal-semiconductor interfaces and its basic phenomena; fabrication procedures; and interface characterization techniques, particularly, ohmic contacts. Contacts that involve polycrystalline silicon; applications of the metal-semiconductor barriers in MOS, bipolar, and MESFET digital integrated circuits; and methods for measuring the barrier height are covered as well. Process engineers, device physicists, circuit designers, and students of this discipline will find the book very useful.

This concise volume examines the characteristic electronic parameters of semiconductor interfaces, namely the barrier heights of metal–semiconductor or Schottky contacts and the valence-band discontinuities of semiconductor–semiconductor interfaces or heterostructures. Both are determined by the same concept, namely the wave-function tails of electron states overlapping a semiconductor band gap directly at the interface. These interface-induced gap states (IFIGS) result from the complex band structure of the corresponding semiconductor. The IFIGS are characterized by two parameters, namely by their branch point, at which their charge character changes from predominantly valence-band- to conduction-band-like, and secondly by the proportionality factor or slope parameter of the corresponding electric-dipole term, which varies in proportion to the difference in the electronegativities of the two solids forming the interface. This IFIGS-and-electronegativity concept consistently and quantitatively explains the experimentally observed barrier heights of Schottky contacts as well as the valence-band offsets of heterostructures. Insulators are treated as wide band-gap semiconductors.

. It is directed to microelectronics and optoelectronics industry researchers, designers, prototype builders, and process engineers. Researchers in physics, applied physics, electrical engineering and the materials science will also find this book an essential reference.

Using the continuum of interface-induced gap states (IFIGS) as a unifying theme, Mönch explains the band-structure lineup at all types of semiconductor interfaces. These intrinsic IFIGS are the wave-function tails of electron states, which overlap a semiconductor band-gap exactly at the interface, so they originate from the quantum-mechanical tunnel effect. He shows that a more chemical view relates the IFIGS to the partial ionic character of the covalent interface-bonds and that the charge transfer across the interface may be modeled by generalizing Pauling?s electronegativity concept. The IFIGS-and-electronegativity theory is used to quantitatively explain the barrier heights and band offsets of well-characterized Schottky contacts and semiconductor heterostructures, respectively.

E se non che di cid son vere prove A nd were it not for the true evidence Per piti e piti autori, che sa, ra. nno Of many authors who will be Per i miei versi nominati altrove, Mentioned elsewhere in my rhyme Non presterei alla penna 10. mana I would not lend my hand to the pen Per nota1' cid ch'io vidi, can temenza And describe my observations, for fear ehe non fosse do. altri casso e van 0; That they would be rejected and in vane; Mala lor chiara. e vera. esperienza But these authors' clear and true experience Mi assicura. nel dir, come persone Encourages me to report, since they Degne di fede ad ogni gra. n sentenza. Should always be trusted for their word. [From" Dittamondo", by Fazio degli UbertiJ Heterojunction interfaces, the interfaces between different semiconducting materi als, have been extensively explored for over a quarter of a century. The justifica tion for this effort is clear - these interfaces could become the building blocks of lllany novel solid-state devices. Other interfaces involving semiconductors are al ready widely used in technology, These are, for example, metal-semiconductor and insulator-semiconductor junctions and hOll1ojunctions. In comparison, the present applications of heterojunction int. erfaces are limited, but they could potentially becOlne lnuch lllore ext. ensive in the neal' future. The path towards the widespread use of heterojunctions is obstructed by several obstacles

This second edition brings a greatly expanded treatment of the physics of Schottky-barrier formation to its comprehensive discussion of modern semiconductor technology. Topics covered include the current/voltage relationship, the capacitance of rectifying contacts, and practical methods of fabricating contacts. Written for semiconductor technologists and physicists engaged in research on semiconductor interfaces, this text emphasizes practical implications wherever they are relevant to device technology.