Electronic Properties of Semiconductor Interfaces
In this chapter we investigate the electronic properties of semiconductor interfaces. Semiconductor devices contain metal–semiconductor, insulator–semiconductor, insulator–metal and/or semiconductor–semiconductor interfaces. The electronic properties of t
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8. Electronic Properties of Semiconductor Interfaces
Electronic Pro
In this chapter we investigate the electronic properties of semiconductor interfaces. Semiconductor devices contain metal–semiconductor, insulator–semiconductor, insulator–metal and/or semiconductor–semiconductor interfaces. The electronic properties of these interfaces determine the characteristics of the device. The band structure lineup at all these interfaces is determined by one unifying concept, the continuum of interface-induced gap states (IFIGS). These intrinsic interface states are the wavefunction tails of electron states that overlap the fundamental band gap of a semiconductor at the interface; in other words they are caused by the quantum-mechanical tunneling effect. IFIGS theory quantitatively explains the experimental barrier heights of wellcharacterized metal–semiconductor or Schottky contacts as well as the valence-band offsets of semiconductor–semiconductor interfaces or
Experimental Database ........................ 149 8.1.1 Barrier Heights of Laterally Homogeneous Schottky Contacts . 149 8.1.2 Band Offsets of Semiconductor Heterostructures ....................... 152
8.2
IFIGS-and-Electronegativity Theory ....... 153
8.3
Comparison of Experiment and Theory .. 8.3.1 Barrier Heights of Schottky Contacts .................. 8.3.2 Band Offsets of Semiconductor Heterostructures ....................... 8.3.3 Band-Structure Lineup at Insulator Interfaces ...............
8.4
155 155 156 158
Final Remarks ..................................... 159
References .................................................. 159 semiconductor heterostructures. Insulators are viewed as semiconductors with wide band gaps.
the very simple and therefore attractive Schottky–Mott rule, Bardeen [8.5] proposed that electronic interface states in the semiconductor band gap play an essential role in the charge balance at metal–semiconductor interfaces. Heine [8.6] considered the quantum-mechanical tunneling effect at metal–semiconductor interfaces and noted that for energies in the semiconductor band gap, the volume states of the metal have tails in the semiconductor. Tejedor and Flores [8.7] applied this same idea to semiconductor heterostructures where, for energies in the band-edge discontinuities, the volume states of one semiconductor tunnel into the other. The continua of interface-induced gap states (IFIGS), as these evanescent states were later called, are an intrinsic property of semiconductors and they are the fundamental physical mechanism that determines the band-structure lineup at both metal–semiconductor contacts and semiconductor heterostructures: in other words, at all semiconductor interfaces. Insulator interfaces are also included in this, since insulators may be described as wide-gap semi-
Part A 8
In his pioneering article entitled Semiconductor Theory of the Blocking Layer, Schottky [8.1] finally explained the rectifying properties of metal–semiconductor contacts, which had first been described by Braun [8.2], as being due to a d
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