摘要:

The generally strong chemical interactions between semiconductors and metals introduce additional complexities in the experimental characterization and modelling of epitaxial growth. This article reviews the relevant epitaxial parameters and growth modes in relation to what is known to occur on semiconductors. A salient property of some metals and semimetals is their tendency to form covalent bonds, whose directionality strongly influences the epitaxial relationship between substrate and overgrowth. Both the substrate orientation and, for the binary semiconductors, the stoichiometry of the substrate, strongly influence the epitaxial relationships. Representative examples of the different growth modes are discussed in relation to interfacial bonding, with emphasis on the growth differences between Al, a reactive metal, and Ag, a nonreactive metal on GaAs. The latter part of the article discusses some of the outstanding issues of the epitaxy of metals on semiconductors and possible approaches to their solution.

ISSN:1071-1023    

DOI:10.1116/1.582833

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582834

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

The heats of solution and substitution for one semiconductor in another are important quantities for an understanding of heterojunction formation. Harrison’s universal‐parameter tight‐binding method (1983) is used to obtain predictions for these quantities and for cohesive energies, defect formation energies, and solid‐state core shifts as well. The cohesive energies and solid‐state core‐shifts are compared with experiment and antistructure defect energies are compared with earlier calculations by Van Vechten. Cohesive energies are accurate to about one‐half an electron volt per bond. Agreement between experimental and theoretical cohesive energy differences is better. Predicted heats of solution and substitution depend on cohesive energy differences and therefore are likely to be realiable and are in accord with experiment in the few cases where experimental values are available. Antistructure defect formation energies agree well with Van Vechten’s earlier work. Predicted solid‐state core shifts are only accurate to a few electron volts.

ISSN:1071-1023    

DOI:10.1116/1.582835

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582885

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582886

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

We present the first report of RHEED intensity changes and recovery as a function of monolayer and submonolayer MBE depositions of InxGa1−xAs (x≤0≤0.5) on GaAs(100) substrates. The influence of the lattice mismatch‐induced strain on the growth mechanisms and the incorporation behavior of In and Ga is suggested by new and In concentration dependent effects in the RHEED intensity waveform behavior during growth. The monolayer oscillation period is determined by the combined In and Ga fluxes. The initial growth of InGaAs on GaAs(100) is planar, but after an amount of deposition depending upon InAs content and growth conditions, a sudden change from a streaked reflection pattern to a spotty transmission pattern is observed indicating formation of 3D islands. The film thickness at which this transition occurs is strongly influenced by the step density of the GaAs surface when InGaAs growth is initiated. We have examined the recovery behavior of the specular spot intensity after the growth of 0.1 to 15 monolayers of GaAs on an annealed metal‐stabilized GaAs(100) surface. In this experiment, the RHEED intensity has dropped from its initial (no‐growth) value and, after termination of growth, it slowly recovers to its steady‐state value. We report RHEED intensity recovery rates as a function of the number of monolayers of GaAs deposited and compare them to recovery rates after steady‐state growth has been reached. The recovery rate is a strong function of the completeness of the surface when growth is stopped.

ISSN:1071-1023    

DOI:10.1116/1.582887

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582888

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

We report on the energetics for the epitaxial growth of metals on semiconductors and obtain optimal interplanar distances using the self‐consistent pseudopotential method. A prototype system for which the lattice mismatch is not too severe has been considered so that the lattice can strain elastically to achieve coherency. An example of such a system is Al(001)–Ge(001) in an epitaxial relation (001)[100]Al∥(001)[110]Ge where the [100]Al axis has been rotated 45° with respect to the Ge [100]axis. We have investigated the pseudomorphic growth of Al from submonolayer to multilayers (in various registry patterns) on the rigid unreconstructed Ge(001) substrate. One significant result of our calculation is that the A1–Ge bond length relaxes as one goes from submonolayer to multilayer coverages of metal indicating a transition from directional covalent to more metallic type of bonding. Another important conclusion is that at monolayer coverages, aluminum at bridging positions in the first layer is more stable (∼1 eV) than at on top positions. This suggests that Frank–van der Merwe growth sequence is likely to initiate at the bridging sites. Furthermore, the energy lost due to an overall strain in pseudomorphically growing many layers is estimated to be well below the energy benefit due to interfacial bonding in bridging sites. We also report that the calculated interfacial bonding energy and the interplanar separation reaches limiting values at about one monolayer coverage, but other properties show slow convergence. The implications of these results for the electronic structure of interfaces and Fermi‐level pinning are briefly investigated.

ISSN:1071-1023    

DOI:10.1116/1.582889

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

A brief critical review is given of diverse techniques used to measure heterojunction band lineups; they range from very reliable to worthless. Another problem pertains to the heterosystems themselves: Data on systems in which two semiconductors from a different pair of columns of the periodic table are combined, should be reviewed with suspicion, although some selected pairs are probably trustworthy—but none in which a compound semiconductor was grown on an elemental one. Technologies that do not lead to device‐quality interfaces also probably do not yield device‐quality lineup data. A list of the most trustworthy experimental data is given. The simplest possible theoretical framework for a theory of band lineups is a model of linear superpositon of atomiclike bulk potentials. Such a model automatically leads to a theory that is linear and transitive, in which the band lineups are orientation independent, and in which a technology dependence of the band lineups requires a technology‐dependent deviation of the atomic arrangement from the ideal one. The Harrison theory is both the simplest and the most successful theory of band lineups, although it still does not meet the needs of the device physicist. The set of most reliable data selected earlier agree very well with this theory, with a largest deviation of 0.18 eV and a standard deviation of 0.13 eV.

ISSN:1071-1023    

DOI:10.1116/1.582890

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

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.

ISSN:1071-1023    

DOI:10.1116/1.582891

出版商:American Vacuum Society    

年代:1984

数据来源: AIP