Schottky势垒高度理论计算中的平均键能方法

以平均键能Em作为参考能级，计算了１０种不同半导体的Schottky接触势垒高度，计算值与实验值符合较好-计算值与实验值的符合程度与Tersoff的电中性能级EB方法相当，优于Harrison和Cardona等人采用sp3平均杂化能εh和介电函数隙中能级ED的计算结果- 关键词： 势垒高度 平均键能方法 费米能级     

Photosensitivity and Schottky barrier height in Au-n-GaAs structures

The photosensitivity spectra of Au-n-GaAs Schottky barriers obtained by the chemical method are studied in the spectral range 0.9–2.2 eV. The barrier height is determined for the structures exposed on the side of the semitransparent Au layer and on the opposite side of GaAs at T = 300 K. It is found that, as the structures are illuminated on the side of GaAs, their photosensitivity in the Fowler spectral region, hν = 0.95–1.25 eV, is approximately one order of magnitude higher than when the barrier contact is illuminated. This circumstance may find use in studying the fundamental properties of the metal-semiconductor and metal-insulator-semiconductor interfaces, as well as in elaboration of new semiconductor devices.     

Schottky barrier height and reverse current of the n-Si-electrolyte junction

We present a new set of results on the current-voltage and capacitance-voltage characteristics of the n-Si-aqueous electrolyte interface. The extreme sensitivity of these characteristics to surface defects has been realized, and defect-free surfaces have been obtained by using a mechanochemical polishing method. A transient technique has allowed us to measure the anodic current density for the oxide-free surface. We have performed these experiments for samples of various donor concentrations and electrolytes of various pH. In each case the flat-band potential and Schottky barrier height have been obtained. The results show that the process for anodic current is thermally activated electron transfer from surface states over the Schottky barrier, and not electron-hole pair generation in the depletion region, as was previously believed.     

Investigation on the barrier height and inhomogeneity of nickel silicide Schottky

The apparent Schottky barrier height (SBH) of the nickel silicide Schottky contacts annealed at different temperatures was investigated based on temperature dependence of I-V characteristic. Thermionic emission-diffusion (TED) theory, single Gaussian and double Gaussian models were employed to fit I-V experimental data. It is found the single Gaussian and double Gaussian SB distribution model can give a very good fit to the I-V characteristic of apparent SBH for different annealing temperatures. Also, the apparent SBH and the leakage current increase with annealing temperatures under reverse voltage. In addition, the homogeneity of interfaces for the samples annealed at temperatures of 500 and 600 °C is much better than that of the samples annealed at temperatures of 400, 700, and 800 °C. This may result from the phase transformation of nickel silicide due to the different annealing temperatures and from the low Schottky barrier (SB) patches.     

Controlled modification of Schottky barrier height by partisan interlayer

A comprehensible and systematic method to modify the Schottky barrier height (SBH), based on the adjustment of the semiconductor electron affinity through adsorbate termination, is demonstrated. Atomic layers of As and Cl, inserted at the metal-Si(111) interface and preferentially bonded to Si, are shown to shift the SBH by as much as 0.40 eV. The (partial) preservation of surface dipole at the metal-semiconductor (MS) interface is likely attributable to the chemical stability of adsorbate-terminated semiconductor surfaces. Experimental and theoretical results are presented to demonstrate the validity of the concept and the effectiveness of SBH adjustment through such “partisan” interlayers. The general implications of these results for the theoretical understanding and the practical control of the SBH are also discussed.     

Tayloring of the Schottky barrier height of Pt-Ir mixed silicide infrared detectors

 Pt-Ir silicide Schottky diodes were formed by e-beam evaporation of Pt and Ir onto p-Si(100) substrates in high vacuum with subsequent RTA-annealing at temperatures in the range of 300 to 500 °C. Rutherford Backscattering Spectrometry (RBS) and infrared photoresponse (PR) measurements were performed to determine the composition and the infrared electrooptical properties of the resulting films. Coevaporated Pt-Ir films are demixed during silicidation and form a PtSi layer at the interface to the silicon substrate. The Schottky barrier height is that of a pure PtSi film. Ir deposited prior to Pt exhibits Pt diffusion through the Ir layer. Only when the Ir film is reacted to IrSi by in situ annealing prior to Pt deposition, a mixed Ir-Pt silicide Schottky barrier is obtained. Infrared photoemission then yields intermediate Schottky barrier heights between those of PtSi and IrSi. From a detailed analysis of the photoemission characteristics, it is concluded that the intermediate barrier height is due to an area average of PtSi and IrSi grains which coexist at the Si interface. Received: 29 May 1996/Accepted: 12 August 1996     

Unoccupied surface states and surface barrier in metals

Recent progress in the spectroscopy of empty electronic states at metal surfaces allows for measuring the energy vs. momentum dispersion of both crystal-induced and image-potential surface states with high precision. This allows for deriving the effective barrier potential for an electron near a metal surface with considerable accuracy by comparing the experimental data with corresponding calculations based on the one-step model of inverse photoemission. The method is demonstrated for Cu(100) where four empty surface states are known experimentally.     

Influence of the interface structure on the barrier height of homogeneous Schottky contacts

Unreconstructed interfaces may be prepared by evaporation of thick Pb films onto surfaces at room temperature. Current-voltage and capacitance-voltage characteristics of such Schottky contacts were measured in the temperature range between 140 and 300 K. The experimental data are analyzed by applying the thermionic-emission theory of inhomogeneous metal-semiconductor contacts as well as the “standard” thermionic-emission theory. From both methods the Schottky barrier height of laterally homogeneous contacts results as 0.724 eV. This value is by 74 meV larger than the previously observed barrier heights of laterally homogeneous interfaces. Similar differences were reported for unreconstructed and reconstructed Al- and contacts. The reduced barrier heights of all these interfaces are explained by the electric dipole associated with the stacking faults of reconstructions at surfaces and interfaces. Received: 14 May 1998 /Revised and Accepted: 7 September 1998     

The barrier height inhomogeneity in Al/p-Si Schottky barrier diodes with native insulator layer

The current-voltage (I-V) characteristics of Al/p-Si Schottky barrier diodes (SBDs) with native insulator layer were measured in the temperature range of 150-375 K. The estimated zero-bias barrier height Φ_B0 and the ideality factor n assuming thermionic emission (TE) theory show strong temperature dependence. Evaluation of the forward I-V data reveals an increase of zero-bias barrier height Φ_B0 but decrease of ideality factor n with increase in temperature. The conventional Richardson plot exhibits non-linearity below 250 K with the linear portion corresponding to activation energy of 0.41 eV and Richardson constant (A^*) value of 1.3 × 10⁻⁴ A cm⁻² K⁻² is determined from intercept at the ordinate of this experimental plot, which is much lower than the known value of 32 A cm² K² for holes in p-type Si. Such behavior is attributed to Schottky barrier inhomogene ties by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Also, Φ_B0 versus q/2kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of Φ_B0 = 1.055 eV and σ₀ = 0.13 V for the mean BH and zero-bias standard deviation have been obtained from this plot, respectively. Thus, the modified versus q/kT plot gives Φ_B0 and A^* as 1.050 eV and 40.08 A cm⁻² K⁻², respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 40.03 A cm⁻² K⁻² is very close to the theoretical value of 32 A K⁻² cm⁻² for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/p-Si Schottky barrier diodes with native insulator layer can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights.     

Spectrum and nature of surface states

With the help of an approximative E(k) relation in the forbidden gap N(E) distributions for localized states are calculated. A potential fluctuation model gives energy distributions of states in the gap which exhibit features of surface state spectra or spectra of disordered systems. Binding and nonbinding states are coupled to pairs by the E(k) relation and characteristic properties of surface and interface state spectra like symmetry, acceptordonor character, minimum of the N(E) distribution may be described. Dangling bonds of preferential 111 character are the proper chemical picture. Approximative energy calculations show a preferential energy range for isolated interface states at a distance of 0.1–0.2 eV distance from the band edges. Comparison with experimental termspectra shows a good agreement with the treated model. Common characteristics of clean, ordinary and oxidized surfaces and the metal semiconductor contact are revealed.     

Modification of Al/Si interface and Schottky barrier height with chemical treatment

The influence of different chemical treatments on the electrical behaviour of n- and p-type Al/Si Schottky junctions was studied. A Schottky barrier height of 0.91 eV was achieved on p-type Si probably due to the unpinning of the Fermi-level at the Al/Si interface. This is one of the highest barrier height values reported so far for a solid-state Schottky junction prepared to p-Si. A doping level reduction was observed in the vicinity of the Si surface for wafers with native oxide and for those boiled in acetone or annealed in forming gas. It was observed unexpectedly that the reactive plasma etch used for the formation of mesa structures decreases the apparent Schottky barrier height. The relation between the sum of n- and p-type Schottky barrier heights and forbidden gap is discussed.     

Prediction of lateral barrier height in identically prepared Ni/n-type GaAs Schottky barrier diodes

We have identically prepared Ni/n-GaAs/In Schottky barrier diodes (SBDs) with doping density of 7.3 × 10¹⁵ cm⁻³. The barrier height for the Ni/n-GaAs/In SBDs from the current-voltage characteristics have varied from 0.835 to 0.856 eV, and ideality factor n from 1.02 to 1.08. We have determined a lateral homogeneous barrier height value of 0.862 eV for the Ni/n-GaAs/In SBD from the experimental linear relationship between barrier heights and ideality factors.     

Highly reproducible ideal SiC Schottky rectifiers: effects of surface preparation and thermal annealing on the Ni/6H-SiC barrier height

In this work, the effects of surface preparation and thermal annealing on the Ni/6H-SiC Schottky barrier height were studied by monitoring the forward I–V characteristics of Schottky diodes. The ideality factor n and the barrier height _B were found to be strongly dependent on the impurity species present at the metal/SiC interface. The physical mechanism which rules the Schottky barrier formation is discussed by considering the nature of the impurities left from the different surface preparation methods prior to metal deposition. In contrast, nickel silicide/SiC rectifiers (Ni₂Si/6H-SiC), formed by thermal reaction of Ni/6H-SiC above 600 °C, have an almost ideal I–V curve, independent of the surface preparation. Further improvement in the barrier height distribution can be obtained by increasing the annealing temperature to 950 °C. This behaviour is discussed in terms of the silicide phases and the consumption of a SiC layer during the thermal reaction. PACS 73.30.+y; 81.65.Cf; 81.05.Je     

The modulation of Schottky barrier height of NiSi/n-Si Schottky diodes by silicide as diffusion source technique

This paper reports that the Schottky barrier height modulation of NiSi/n-Si is experimentally investigated by adopting a novel silicide-as-diffusion-source technique, which avoids the damage to the NiSi/Si interface induced from the conventional dopant segregation method. In addition, the impact of post-BF₂ implantation after silicidation on the surface morphology of Ni silicides is also illustrated. The thermal stability of Ni silicides can be improved by silicide-as-diffusion-source technique. Besides, the electron Schottky barrier height is successfully modulated by 0.11~eV at a boron dose of 10¹⁵~cm^-2 in comparison with the non-implanted samples. The change of barrier height is not attributed to the phase change of silicide films but due to the boron pile-up at the interface of NiSi and Si substrate which causes the upward bending of conducting band. The results demonstrate the feasibility of novel silicide-as-diffusion-source technique for the fabrication of Schottky source/drain Si MOS devices.     

Determination of the laterally homogeneous barrier height of thermally annealed and unannealed Au/p-InP/Zn-Au Schottky barrier diodes

We have identically prepared Au/p-InP Schottky barrier diodes (SBDs). The diodes were annealed up to 400 °C thermally. The barrier height (BH) for the as-deposited Au/p-InP/Zn-Au SBDs from the current-voltage characteristics have varied from 0.58 to 0.72 eV, and ideality factor n from 1.14 to 1.47. The BH for the annealed SBDs from the current-voltage characteristics have varied from 0.76 to 0.82 eV, and ideality factor n from 1.17 to 1.39. As a result of the thermal annealing, it has been seen that the BH values of the annealed SBDs are larger than those of the as-deposited SBDs. We have determined a lateral homogeneous BH value of 0.72 eV for the as-deposited Au/p-InP SBD from the experimental linear relationship between barrier heights and ideality factors, and a value of 0.85 eV for the annealed Au/p-InP SBD. The increase of 0.13 eV in the BH value by means of 400 °C annealing has been ascribed to the formation of the excess charges that electrically actives on the semiconductor surface.     

Bulk and surface electron states in ruthenium

Using ab initio pseudopotentials and a mixed basis, we have examined the electronic structure of ruthenium. We have concentrated on the bulk and surface energy bands with specific emphasis on the close packed (0 0 0 1) surface. We present energy band spectra for the surface and bulk bands, and compare these bands to experiment and to other calculations. We find good agreement between our bulk bands and recent photoemission measurements. With respect to our surface bands, the results are in good accord with other calculations both for ruthenium and for “analogous” transition metal surfaces.