摘要:

Theoretical predictions of electronic energy levels associated withs‐ andp‐bonded substitutional point defects at (110) surfaces of InAs and other III–V semiconductors are presented and discussed. The specific defects considered for InAs are: anion and cation vacancies, the (native) antisite defects InAsand AsIn, and 26 impurities. The predicted surface‐defect deep levels are used to interpret Schottky barrier height data for (a)n‐ andp‐(InAs) and (b) the alloys AlxGa1−xAs, GaAs1−xPx, In1−xGaxP, and In1−xGaxAs. The rather complicated dependence of the Schottky barrier height φBon alloy compositionxprovides a nontrivial test of the theory (and competing theories). The following unified microscopic picture emerges from these and previous calculations: (1) For most III–V and group IV semiconductors, Fermi‐level pinning by native defects can explain the observed Schottky barrier heights. (2) For GaAs, InP, and other III–V semiconductors interfaced with nonreactive metals, the Fermi‐level pinning is normally due to antisite defects. (3) When InP is interfaced with a reactive metal, surface P vacancies are created which pin the Fermi level. (4) Impurities and defect complexes are sometimes implicated. (5) At Si/transition‐metal‐silicide interfaces, Si dangling bonds pin the Fermi level. (6) These defects at the semiconductor/metal interfaces are often ‘‘sheltered’’ or ‘‘encapsulated.’’ That is, the states responsible for Fermi‐level pinning are frequently ‘‘dangling‐bond’’ states that dangle into a neighboring vacancy, void, or disordered region. The defects are partially surrounded by atoms that are out of resonance with the semiconductor host, causing the defect levels to be deep‐level pinned and to have energies that are almost independent of the metal.

ISSN:1071-1023    

DOI:10.1116/1.582893

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Various models of Schottky barrier formation have been proposed in the last few years which involve metallurgical interactions at the metal–semiconductor interface. Most of these models involve nonuniform lateral variations in the surface potential. For metallic clusters and/or anion clusters, these variations involve a relatively large size scale (tens to hundreds of angstroms). For interface defect formation, the suggestion of cluster formation energy as the driving force for defect formation could also lead to a nonuniform distribution of pinning sites on a similar size scale. We have studied the effects of various spatial distributions of pinning sites (e.g., surface defects, clusters of anions and/or adsorbed metal atoms) and variations of their energy levels upon surface potentials and their depth distribution via a two‐dimensional finite difference program that integrates Poisson’s equation. Our results suggest that surface sensitive spectroscopies provide a less than exact measure of pinning levels in many such cases. For example, for 1018n‐GaAs and pinning site separation of 100 Å, our calculations imply a Kelvin probe band‐bending result for the surface potential of ≊0.15 V less than the ‘‘pinning’’ value (for pinning values of 0.8 and 0.6). Furthermore, such nonuniform distributions alter the effect of probe depth. The surface potential determined via e.g., UPS, with a 20 Å mean free path, would differ from the ‘‘true’’ surface averaged value by ≊0.09 eV for a uniform 0.8 V surface; while this difference is ≊0.07 for 100 Å separations, and ≊0.05 for 400 Å separations, theratioof this λ dependent term to the total measured band bending increases as the distance between pinning sites increases. Note that a pinning level 0.8 eV below the conduction band minimum leads (under the assumptions of 100 Å between sites, probe depth ≊20 Å, and 1018cm−3bulk doping) to a ‘‘measured’’ surface potential within 0.6 eV of the conduction band minimum. These results should impact the interpretation of surface dependent studies of Schottky barrier formation, especially for specific models of such formation.

ISSN:1071-1023    

DOI:10.1116/1.582895

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Capacitance–voltage and current–voltage characteristics at single crystal silicide–silicon interfaces are studied. Schottky barrier heights are determined for epitaxial NiSi2and CoSi2layers grown under ultrahigh vacuum conditions on Si(111). These results demonstrate that there is an influence of interface structure on Schottky barrier height. This dependence suggests a reassessment of many previous interpretations or models of Schottky barriers. It also shows that experimentally measured barrier heights of metal–semiconductor systems with inhomogeneous interface structure are likely to be the averages from those associated with different regions of the interface. Homogeneous metal–semiconductor interfaces are therefore the simplest and most desirable systems for the study of Schottky barrier mechanisms. In particular, the present epitaxial silicide–silicon interfaces represent ideal candidates for detailed theoretical investigations based on experimentally obtained atomic structures.

ISSN:1071-1023    

DOI:10.1116/1.582896

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

We present a photoemission study of the valence band discontinuity ΔEvand the Fermi levelEFat the abruptn‐GaAs/Ge interface. We investigated these properties during the early stages of interface formation between different reconstructions of GaAs(100) and epitaxial Ge. While GaAs(100) As surface stoichiometry variations from 0.25 to 1.25±0.10 monolayers caused no change in ΔEv, the Fermi position indicated an increasinglyn‐type interface of>0.3 eV with the presence of As. Intentional As4annealing of the Ge or addition into the growth environment only produced a moren‐type barrier with no corresponding change in ΔEv. Variations in crystallographic orientations do not contribute to the band discontinuities by more than ±0.05 eV.

ISSN:1071-1023    

DOI:10.1116/1.582897

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Stimulated by the work of Zur, McGill, and Smith (ZMS), we have undertaken a broad examination of the ‘‘potential normalization’’ conditions at the metal–semiconductor interface. We have made calculations using a metallic approximation and the model of Bardeen. Strong overall agreement is found with the results of ZMS; however, the details depend on the specific parameters used in the calculations. In particular, parameters were identified which give different pinning positions onn‐ andp‐type semiconductor materials. Experimentally, Cs is found to be in strong disagreement with any ‘‘metallic’’ approximation at the interface; rather, it is shown that the experimental and theoretical understanding of Cs on solids indicates that an atomic model for the last atomic layer of Cs (with some fixed charge due to the induced Cs atomic dipole at the interface) is a more appropriate approximation than the metallic approximation used by ZMS and ourselves. Experimental results for thick noble metals (Au, Cu, and Ag) depositedinsituon clean GaAs(110) formed by cleaving in UHV are reported. These give a pinning position at the donor level as do properly analyzed PES measurements on thin (sub‐ to full‐monolayer) deposits of noble metals on GaAs. An atomic explanation based on the large electron affinity of the noble metals is suggested and this is related to the interfacial chemistry. In contrast, significant differences are found between the thin and thick pinning positions of Al on GaAs in general agreement with the metallic approximations of ZMS and ourselves.

ISSN:1071-1023    

DOI:10.1116/1.582898

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Semiconductor valence‐band edges are computed on absolute energy scales determined by Herman‐Skillman and Hartree–Fock neutral atom ionization energies, respectively. These calculations use Harrison’s (1977) elementary theory of heterojunctions. Differences are compared with experimental heterojunction band discontinuities. It is shown that calculations based on Herman–Skillman neutral atom energies and Harrison’s original solid‐state matrix elements agree somewhat better with experiment than later results (1981) based on Hartree–Fock neutral atom energies and modified solid‐state matrix elements. Although no simple theory for heterojunction core‐level discontinuities seems to exist, it is shown that the experimentally measured heterojunction core‐level discontinuities are roughly equal to the binding energy differences of fully relaxed neutral atom core levels such as those calculated by Huang and co‐workers.

ISSN:1071-1023    

DOI:10.1116/1.582900

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Electronic devices can be significantly affected in their behavior by the properties of the surfaces and interfaces which delineate their structure. Unfortunately, such surface effects are often degrading, acting to reduce the performance of the device below that to be expected in the ideal case. This paper will attempt to review these processes and relate them to what is known about the properties and structures of surfaces. In particular those deficiencies which most severely impact device performance will be identified, and suggestions made as to where improvements in understanding of surface control might have the greatest impact on resulting device development.

ISSN:1071-1023    

DOI:10.1116/1.582806

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

As semiconductor devices become smaller, the temporal and spatial scales become sufficiently short and the electric field sufficiently large that new physical constraints are reached in treating the transport of carriers within the devices. These devices are now controlled by strong size‐related effects: coupling to the environment of contacts, interfaces/boundaries/surfaces, interconnects, and other devices. This is especially the case in MOSFET’s, where remote interface phonons and surface roughness scattering dominate the transport. In this talk, a general treatment of device–environment interaction will be discussed. Special cases for MOS transport and the specific role of interfaces will be treated.

ISSN:1071-1023    

DOI:10.1116/1.582807

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.582808

出版商:American Vacuum Society    

年代:1984

数据来源: AIP

摘要:

Electrical measurements on two‐terminal structures and on A‐MISFET’s, with 20 and 30 μm long channels, fabricated on SiO2or Al2O3coated semi‐insulating InP, indicate that charge transport between their Au–Ge eutectic contacts takes place by a combination of electron transport in the accumulation layer and space charge limited current flow, both affected by deep level traps. Following application of a step voltage, the total time dependence current may be described qualitatively byI(t)=I0exp (−t/τ2)+I1[1−exp (−t/τ1], where τ2≫τ1andI0is the accumulation current.

ISSN:1071-1023    

DOI:10.1116/1.582809

出版商:American Vacuum Society    

年代:1984

数据来源: AIP