摘要:

We have performed a photoemission study of the Schottky barrier obtained by depositing Ag onto UHV cleaved GaP(110) at room temperature. The barrier appears to be fully developed at a coverage of ∼2 monolayers and its height is 1.1 eV. This figure is to be compared with higher (lower) values obtained with metals having a larger (smaller) work function than Ag, for example Cu and Au (In and Al) deposited onto the same surface. The result corroborates the idea that the metal–GaP(110) interface is a good example of the Schottky limit in metal–semiconductor junctions. The effective work function model proposed by Woodall and Freeouf provides the best interpretation of the Schottky barrier height in this interface.

ISSN:1071-1023    

DOI:10.1116/1.584715

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

We report the growth by molecular‐beam epitaxy of GaAsSb crystals on GaAs (100) substrates. The composition of the alloyed crystals has been strongly dependent on the growth condition, especially on the substrate temperature and the arrival rates of arsenic and antimony molecules. Raman scattering measurements have been performed to characterize the grown layers, GaAsSb, and GaSb on GaAs substrates. In the GaSb/GaAs grown at relatively high temperatures, we observe the variation of composition near the heterointerface.

ISSN:1071-1023    

DOI:10.1116/1.584716

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The incorporation behavior of thermally evaporated In during the growth of Si(100) by molecular‐beam epitaxy has been observed to depend critically on whether a magnetically focused electron gun (MFG) or electrostatically focused electron gun (EFG) evaporation source was used for Si evaporation. When a MFG source was used, the incorporation probability σ was found to be very low during growth on grounded substrates, but could be increased considerably by the application of a negative substrate bias between 100 and 2000 V. This increase was due to Si+ion bombardment of the In surface overlayer resulting in secondary implantation during growth. For deposition on electrically grounded substrates, σ was found to be much higher during growth with the EFG source than with the MFG source. This was primarily due to bombardment of the In overlayer by energetic neutral Si atoms emitted from the EFG source.

ISSN:1071-1023    

DOI:10.1116/1.584717

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

A study is presented of compositional modulations (i.e., so‐called banding) in heteroepitaxial strained layers of nominally uniform Ge0.1Si0.9grown by molecular‐beam epitaxy (MBE). The oscillatory nature of the modulations is studied by transmission electron microscopy (TEM) techniques and the results show that the contrast modulations have a periodicity of ∼23 nm when 1‐μm‐thick epilayers are grown on a rotated substrate. For growth on an unrotated substrate, contrast modulations are still observed but they are less regular. It is further shown that the electron microscope image features are dominated by strain contrast and not structure factor contrast. The presence of strain is consistent with there being a small change in lattice parameter between adjacent bands of material, together with elastic relaxations afforded by the proximity of the thin‐film surfaces. It is concluded that these variations in the lattice parameter are due to the compositional modulations. Limits on the magnitude (Δx) of the compositional modulations are assessed from considerations of diffraction contrast theory (giving an upper limit) and elasticity theory (giving a lower limit). The upper and lower limits for the compositional modulations, assuming an average 9 at. % Ge–Si epilayer, are ±1 at. % and ±0.25 at. % Ge, respectively. The origin of these compositional modulations is thought to be associated with equipment instabilities or a metastable miscibility gap.

ISSN:1071-1023    

DOI:10.1116/1.584718

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

A molecular‐beam source utilizing single‐filament construction to generate a reproducible and uniform beam of elemental molecules is presented. The filament design is constructed to conform to the shape of pyrolytic boron nitride crucibles utilized in molecular‐beam epitaxy (MBE) systems, and to minimize the thermal gradient between the crucible opening and the crucible bottom which is inherent in Knudsen cell technology. The design also improves heat transfer, efficiency, and flux response of the cell. We show that this cell exhibits a better flux response than typical commercially available effusion cells and successfully prevents source material redistribution, thus providing for long‐term flux stability and reproducibility in certain materials used in MBE. No increase in background impurity concentration in epitaxial AlGaAs films was observed, when compared to films grown using a standard Varian effusion cell. This cell is currently installed and being used as an aluminum source in a Varian GEN II system.

ISSN:1071-1023    

DOI:10.1116/1.584719

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Heteroepitaxial growth of silicon on a germanium surface at 580–800 °C is investigated using Si2H6/H2gas low‐pressure chemical vapor deposition processing. Crystalline Si grows on the Ge film surfaces at temperatures of 650–730 °C and, by contrast, polycrystalline Si is deposited at low temperatures of 580–630 °C. It is clarified that whether crystalline Si grows on the Ge surface depends only on substrate temperature, not on the Si2H6partial pressure (4×10−3–1×10−1Torr) nor the Si growth rate (3–800 nm/min). The growth rate using Si2H6is more than one order higher than the SiH4case. Its activation energy is 1.4 eV.

ISSN:1071-1023    

DOI:10.1116/1.584721

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.584722

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Thin‐film silicide runners were found to be annealed by an electric current through such runners. Results obtained using a 2660‐Å‐thick codeposited Ta–Si film and a current density of 3×105A/cm2, clearly show that such localized annealings can be achieved by use of this method. The possibility of using such technique to selectively anneal upper‐level patterned conductors in the integrated circuits has been suggested.

ISSN:1071-1023    

DOI:10.1116/1.584723

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.584724

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The structural and optical properties of a series of molecular‐beam epitaxy (MBE) grown HgTe–Hg0.15Cd0.85Te superlattices (SL) have been studied. Vertical cross‐section transmission electron microscopy studies show no evidence of Hg interdiffusion, confirming the high quality of these multilayered structures. Transmittance and reflectance measurements were performed on each sample and analyzed to obtain optical absorption coefficients. The absorption coefficient versus photon energy spectra show consecutive rises and plateaus characteristic of two‐dimensional quantum structures. A two‐band tight‐binding model was used to analyze the absorption data and identify the quantum transitions. The observation of both light‐hole and heavy‐hole transitions allowed the determination of both the superlattice band gap and the valence‐band offset. The offset was found to be 300 meV (±20 meV) for the superlattices studied, which extrapolates to 350 meV (±20 meV) for the HgTe–CdTe binary interface.

ISSN:1071-1023    

DOI:10.1116/1.584725

出版商:American Vacuum Society    

年代:1989

数据来源: AIP