A. Zur

We define the concept of lattice match for any pair of crystal lattices in any given crystal direction, allowing for a periodic reconstruction of the interface. An algorithm for a systematic search for all possible matches is developed, and some examples of nonstandard lattice matches are given for CdTe on GaAs and sapphire to illustrate the method. For the case of CdTe on GaAs, our results agree with published results, both with respect to growth plane and orientation for CdTe(111) on GaAs(100). For CdTe on sapphire, our results agree with published results with respect to growth plane.

We have investigated the phenomenon of Fermi-level pinning by charged defects at the semiconductor-metal interface. Two limiting cases were investigated. In the first case we modeled an infinitely thick metallic coverage. In the second case we modeled a submonolayer coverage by using a free semiconductor surface containing defects. In both cases we assumed that most of the defect-induced interface states are localized inside the semiconductor, not more than a few angstroms away from the metal. Under these conditions we have estimated the difference in Fermi-level position between $n$- and $p$-type semiconductors to be less than 0.05 eV in the case of a thick metallic coverage. This difference was shown to be the maximum possible one, and it occurs only when there is no pinning. When there is pinning, this difference is even smaller. No such upper bound on the difference in Fermi-level position exists in the case of submonolayer coverage. We have also found that the defect density required to pin the Fermi level is \ensuremath{\sim}${10}^{14}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ in the case of a thick metallic coverage, but only \ensuremath{\sim}${10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ in the case of a submonolayer coverage.

We have used a systematic search to determine all the possible transition-metal silicides that are geometrically lattice-matched to either the (100), (110), or the (111) face of silicon. A short table with the best possible matches is presented here, and a more comprehensive table including slightly worse matches is deposited with the editor.

The role of defects in heterojunctions was investigated. The density of such defects required to pin the Fermi level or to affect the band offset was estimated using simple electrostatic considerations. We conclude that it is very unlikely that defects play any role in determining the band offsets, but they might affect the Fermi-level position at the interface.

Recent experiments, involving thin coverage of metal atoms on III-V semiconductors, suggest that the Fermi level position at the surface for n- and p-type materials may differ by as much as 0.2 eV (1). However, in measurements of Schottky barriers consisting of a bulk metal against a bulk semiconductor, the Fermi level position at the metal-semiconductor interface is found to be the same for both n- and p-type semiconductors to within 0.1 ev (2). 
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\nTo understand this difference, we have investigated the phenomenon of Fermi level pinning by charged interface states at the semiconductor-metal interface. Two limiting cases were investigated. In the first case, we modeled an interface with infinitely thick metal. In the second case, we modeled a submonolayer coverage by using a free semiconductor surface containing defects. In both cases, we assumed that most of the defect induced interface states are localized a few angstroms inside the semiconductor. Under these conditions we have estimated the difference in Fermi level position between n- and p-type semiconductors to be less than 0.05 eV in the case of the thick metallic coverage, which agrees with the theoretical results of Daw and Smith (3). This difference was shown to be the maximum one, and it occurs only when there is no pinning by the defects. When there is pinning, this difference is even smaller. No such upper bound on the difference in Fermi level position exists in the case of submonolayer coverage. We have also found that the number of interface states required to pin the Fermi level is ≃10^14 cm^-2 in the case of coverage by a thick metal, but only ≃10^12 cm^-2 in the case of a submonolayer coverage.