摘要:

In this paper we present a complete experimental study and theoretical treatment of the barrier height of metal–silicon nitride–silicon Schottky barrier diodes. This study avoids the ambiguities of previous investigations of metal–insulator semiconductor Schottky barriers by use of a more complete and more exact model and a wider range of experimental conditions. The barrier height of these diodes was measured as a function of nitride thickness for a variety of contact metals. From this data the effects of interface traps, fixed charge defects and band lineups can be distinguished from each other and the role that each of these mechanisms plays in determining the barrier height can be ascertained. The barrier height vs metal and barrier height vs thickness data show no signs of the effects of interface traps. Instead, the differences in barrier height observed depend solely on the band lineup at the metal–nitride interface, and fixed charge defects.

ISSN:0734-211X    

DOI:10.1116/1.584589

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The band‐bending behavior at interfaces between thin Cs–oxide films and GaAs(110) is studied by photoemission as a function of overlayer stoichiometry and interfacial reactivity. For a substrate temperature of 140 K, nonreactive Cs–oxide/GaAs(110) interfaces with various Cs–oxide stoichiometries were prepared either by successive Cs and oxygen exposure or by codeposition of Cs and oxygen. A remarkable correlation between overlayer stoichiometry and band bending is observed: For bothn‐ andp‐type substrates, oxygen‐rich overlayers result in almost flat‐band conditions, while Cs‐rich overlayers lead to Fermi‐level positions close to midgap. This behavior is interpreted as a manifestation of a negligible influence of defect states to band bending in the case of these nonreactive interfaces, strongly supporting a mechanism based on virtual gap states. Thermal annealing of the interfaces causes strong interfacial chemical reactions and an increase in band bending for bothn‐ andp‐type substrates, signaling non‐negligible contributions of reaction‐induced defect states in this case.

ISSN:0734-211X    

DOI:10.1116/1.584591

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The formation of the Sb and Sn/InP(110) interfaces has been studiedinsituby soft x‐ray core level photoemission spectroscopy. It is found that in both cases the growth of the first uniform monolayer is followed by the formation of large overlayer islands (Stranski–Krastanov mode). The dramatic sharpening of the substrate core levels at one monolayer of Sb indicates the formation of an ordered epitaxial overlayer. No such effect is seen for Sn for which the In 4dcore level shows an indication of surface disruption. Despite the lack of order, this interface also remains mostly nonreactive. A straightforward analysis of the data for these particularly simple interfaces indicates nonequivalent shifts in the P 2pand In 4dcore levels which are taken as a measure of the band bending. The origin of this discrepancy is shown to be related to an additional interface component in the In 4dcore level data. The results of this study indicate that even for nonreactive InP interfaces one must take this into account in using core level photoemission data for quantitative band bending determination. Interestingly, both Sb and Sn, although nonreactive, appear to form Ohmic contacts to InP(110).

ISSN:0734-211X    

DOI:10.1116/1.584592

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

We describe an investigation of an unreactive interface, namely Sb on InP(110) clean cleaved surfaces. Transport techniques (I–V,C–V), Raman spectroscopy, and soft x‐ray photoelectron spectroscopy have been used to study the Schottky barrier heights, overlayer structure, and interface interactions for Sb layers deposited on substrates held at room and low temperatures. The evolution of the overlayer structure at room temperature is complex, with an amorphous Sb layer growing on top of an ordered monolayer, until a thickness of ∼10 monolayers (ML), when the layer crystallizes. The evolution of the Schottky barrier is also complex but for thick layers we observe the lowest barriers onn‐InP and the highest ever observed onp‐InP. Possible mechanisms for the fact that the Fermi level appears pinned close to the conduction band are discussed.

ISSN:0734-211X    

DOI:10.1116/1.584593

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Photoemission spectra of silicon overlayers on Ag(111) and Ag(100) substrates reveal a significant difference in the interface width with respect to Ag deposited on silicon. The Schottky barrier height derived from our data, although affected by some residual uncertainty on possible band‐bending effects, suggest instead independence of the deposition sequence.

ISSN:0734-211X    

DOI:10.1116/1.584790

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

We report soft x‐ray photoemission studies of metal/molecular‐beam epitaxy (MBE)‐GaAs(100) interfaces formed at low temperature. Our results indicate that rectifying barrier heights are proportional to the metal work function in accordance with Schottky’s original description of metal–semiconductor contacts. These results confirm the predictions of a self‐consistent model of metal–semiconductor interfaces, and suggest that metal‐induced gap states and native defect mechanisms are not major factors in determining the Fermi level energy at ‘‘ideal’’ interfaces. We attribute deviations from the ideal Schottky limit behavior observed for interfaces formed at room temperature to metallization‐induced atomic relaxations (rather than electronic relaxations) occurring at metal–semiconductor contacts. We present a useful methodology for analyzing electronic properties at metal–semiconductor interfaces. The pronounced differences in barrier height formation between MBE vs melt‐grown GaAs can evidence the role of deep states in controlling Schottky barriers at metal/melt‐grown GaAs.

ISSN:0734-211X    

DOI:10.1116/1.584791

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

It is proposed that surfaces of crystals that reconstruct with broken orientational symmetry and exhibit an anisotropic stress tensor are unstable to the formation of elastic stress domains. The ground state of such a surface is not uniform, but corresponds to a mosaic pattern of the different domains. This result is applied together with microscopic calculations of surface stress to study the Si(100) surface. A structural transition from single‐layer to double‐layer steps for vicinal Si(100) surfaces is also studied.

ISSN:0734-211X    

DOI:10.1116/1.584792

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

We present a polarization‐dependent CoK‐edge SEXAFS investigation on the local atomic geometry around Co atoms at the interface between epitaxial CoSi2and Si(111). The Co interface atoms are found to be coordinated with eight Si atoms at CoSi2‐like bond lengths.

ISSN:0734-211X    

DOI:10.1116/1.584793

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

To further explore the mechanism of Schottky barrier formation at a metal–semiconductor interface, high‐resolution electron micrographs were simulated in order to interpret the contrast observed experimentally at Cr/GaAs(110) interfaces. Calculations for a wide range of defocus and sample thickness values, based on an assumed ideal arrangement of atoms at the interface, do not explain the observed contrast. Analytical data suggest that the interface is As rich. In this paper, therefore, only those point defects that lead to As‐rich interfaces were considered. Among such point defects, Ga vacancies seem likely to contribute to such experimentally observed contrast.

ISSN:0734-211X    

DOI:10.1116/1.584794

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The dynamics ofX‐point tunneling in AlAs–GaAs–AlAs double barrier heterostructures is studied with numerical simulation. The problem is formulated within the framework of the one‐band Wannier orbital model which allows for simultaneous descriptions of the Γ‐point double barrier profile and theX‐point double well profile in this heterostructure. Time dependences of the following processes are illustrated: (i) resonant tunneling of Γ‐valley electron packets via theX‐point quantum well states localized in the AlAs layers, (ii) nonresonant tunneling of Γ‐electron packets (with energy below the AlAs Γ‐point barrier) through theX‐point continuum states, and (3) resonant tunneling via Γ‐Xmixed quantum well states localized in both the GaAs Γ‐point quantum well and the AlAsX‐point double quantum well. In addition, the effects ofX‐point tunneling on the escape times of electrons localized in the GaAs quantum wells are examined.

ISSN:0734-211X    

DOI:10.1116/1.584796

出版商:American Vacuum Society    

年代:1989

数据来源: AIP