摘要:

Heteroepitaxy of a highly mismatched system (∼8%), InP/Si, has been studied using low‐pressure organometallic vapor phase epitaxy. GaAs buffer layer effects on residual stress and defect density in InP/Si have been clarified. Using a 1‐&mgr;m‐thick GaAs buffer layer, residual stress in the InP layer has been reduced to as low as 2×108dyn/cm2compared to ∼4×108dyn/cm2for InP directly grown on Si. Moreover, the GaAs buffer layer has also been confirmed to be effective for improving InP/Si quality by evaluation of etch‐pit density, x‐ray diffraction measurement, and cross‐sectional transmission electron microscopy. Electrical properties of InP layers on GaAs/Si were evaluated with the van der Pauw and deep level transient spectroscopy (DLTS) methods. The heteroepitaxial layer’s own electron trap has also been observed by DLTS measurements. For an InP/GaAs/Si structure, InP growth temperature effect on surface morphology and etch‐pit density is also shown. High quality InP films with an etch‐pit density of 8×106cm−2have been obtained on Si substrates by using thermal cycle growth and InP/GaAs/Si structure.

ISSN:0021-8979    

DOI:10.1063/1.346826

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The microprocess of deformation and fracture for pure and Bi‐segregated &Sgr;3(1¯1¯1)/[101] 70.53° and &Sgr;33(5¯4¯5)/[101] 58.99° tilt bicrystals of metal copper has been studied by the molecular dynamics method. It has been found that deformation and fracture are dependent on the grain boundary (GB) structure and bismuth segregation. For pure &Sgr;33 bicrystal, the deformation is mainly due to the glide of partial dislocations generated from the GB structural units where the GB dislocations exist. The ductile fracture is attributed to the dislocation emission, which leads to vacancy generation and void coalescence. The bismuth segregation weakens the atomic bonds between copper atoms in the vicinity of GB. Under the action of the external load, the weakened bonds break and lead to formation of microcracks. Finally, the brittle fracture takes place along the binding weakening region. For &Sgr;3 bicrystal, the ductile fracture is related to the void coalescence generated not by dislocation emission but by lattice distortion, and the brittle fracture induced by bismuth segregation is also caused by the breaking of weakened Cu—Cu bonds.

ISSN:0021-8979    

DOI:10.1063/1.346827

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The first measurement of the material constants of Ta2O5thin films is described.x‐axis‐oriented Ta2O5thin films were deposited on fused quartz using the dc diode sputtering method. The material constants were determined from the phase velocity and the electromechanical coupling constant of the bulk waves and the surface acoustic waves propagating on the layered substrate.

ISSN:0021-8979    

DOI:10.1063/1.346828

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The selective area epitaxy of GaInAs/InP layers grown by low‐pressure metalorganic vapor phase epitaxy through SiO2patterned masks was investigated. The layers are found to develop mesa structures limited by {111} and (100) facets outside of the opened mask, and perfect selective epitaxy is obtained. The absence of GaInAs growth on {111} facets allows the fabrication of very narrow buried GaInAs layers in a single growth step. For both materials, the growth rates are found to depend strongly on the mask geometry owing to surface diffusion of the reactant species from the no‐ or low‐growth SiO2mask and {111} facets toward (100) surfaces. A detailed quantitative analysis is made to identify the critical parameters that control the growth behavior, and a model is described from which the upper limit of the growth rates for any mask design can be calculated. Low‐temperature cathodoluminescence measurements show strong emission of the buried GaxIn1−xAs layers and indicate local stoichiometry variations &Dgr;x&bartil;±5% around thex=47% lattice‐matched composition that are attributed to different diffusion coefficients of the reactant species on the SiO2mask and {111} facets. The results show that selective area metalorganic vapor phase epitaxy is a promising technique for the fabrication of one‐step‐grown buried quantum‐well wire arrays and narrow cavity InP‐based buried lasers.

ISSN:0021-8979    

DOI:10.1063/1.346829

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The role of normal absorption in x‐ray diffraction measurements of integrated Bragg intensities from epitaxial (or other) layers and their associated substrates is discussed in terms of the transmission factor. It is shown that the technique for the determination of the polarity of an epitaxial layer by means of anomalous scattering of x rays need not be limited to the case of an effectively infinite layer thickness, in Bragg geometry. Some discussion of layer‐thickness determination is also given.

ISSN:0021-8979    

DOI:10.1063/1.346808

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper reports the growth of pinhole‐free epitaxial YSi2−xlayers on Si(111) as thin as 30 A˚. This has been accomplished by depositing both Y and Si at room temperature and then annealing to 500–900 °C. Use of the template method allows for the growth of thicker films also free of pinholes. Deposition of yttrium metal only onto Si(111) requires a temperature ∼300 °C for nucleation of the silicide reaction between the Y overlayer and Si substrate. Such a process creates small pinholes ∼500 A˚ in diameter, randomly distributed throughout the film. These pinholes increase in size with higher annealing temperature, resulting from a raised interface free energy intrinsic to the nucleation controlled growth.

ISSN:0021-8979    

DOI:10.1063/1.346809

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Conditions have been developed for the deposition of stoichiometric thin films of amorphous gallium arsenide by the technique of flash evaporation. Structural properties of as‐deposited and annealed thin films ofa‐GaAs have been studied using x‐ray diffraction and transmission electron microscopy techniques. The as‐deposited films are noncrystalline, structural ordering starts at about 200 °C, and the film becomes crystalline at about 400 °C with the structure matching with that of polycrystalline GaAs. The as‐depositeda‐GaAs thin films have been passivated using hydrogen plasma under different conditions. The influence of hydrogenation on thesea‐GaAs films has been studied using Fourier transform infrared absorption spectroscopy. These data are explained in terms of the various types of hydrogen bondings and the results are in excellent agreement with the earlier investigations ona‐GaAs:H.

ISSN:0021-8979    

DOI:10.1063/1.346810

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

AlxN1−xfilms were prepared on GaAs(110) surfaces at room temperature by simultaneous evaporation of aluminum and exposure to a beam of ammonia molecules (reactive molecular‐beam epitaxy). The formation of aluminum nitride was followed by using photoemission spectroscopy excited with ZrM&zgr; radiation (h&ngr;=151.2 eV). The composition of the deposited films was monitored by recording the N(1s) and Al(2p) core lines excited with MgK&agr; radiation (h&ngr;=1253.6 eV). The intensity ratio of these core levels as a function of impinging rate ratioz=&ngr;(NH3)/&ngr;(Al) was compared with the intensity ratio determined with an AlN standard under the same experimental conditions. Aluminum nitride was found to form at room temperature forzvalues larger than some 104.

ISSN:0021-8979    

DOI:10.1063/1.346811

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have employed a first‐principles computer program to simulate actual potential profiles and potential profiles obtained experimentally from the Kelvin probe technique. Our results show that the Kelvin probe technique can be used as aninsitumethod for qualitatively characterizing amorphous films and structures during deposition. However, without additional information about the density and energy distribution of localized states in the bulk and at the free surface, we find that it is difficult to obtain, from the Kelvin probe measurement alone, an accurate quantitative measure of the actual spatial dependence of band bending in films and device structures. In addition, this computer analysis shows that interpretation of the profiles obtained from the Kelvin probe contact potential method can lead to misleading conclusions about the density of states in these amorphous materials. We also show that the barrier height of Schottky contacts or the built‐in potential of junctions of differently doped layers can be obtained directly from Kelvin probe contact potential measurements only for films whose free‐surface band bending is known from other experimental data. We see that this surface band bending can be significant even for small free‐surface‐state densities and is more pronounced in higher‐quality films.

ISSN:0021-8979    

DOI:10.1063/1.346812

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Transient decay of persistent photoconductivity (TDPPC) measurements were performed and analyzed in terms of models in which the TDPPC is associated with thermally activated electron capture into DX and a modification of the ionized impurity density, and hence the mobility, concomitant with electron capture. Quantitative agreement between theory and experiment was possible when Chadi and Chang’s model for DX [Phys. Rev. Lett.61, 873 (1988); Phys. Rev. B39, 10063 (1989)] was employed in conjunction with a photo‐induced shallow donor.

ISSN:0021-8979    

DOI:10.1063/1.346785

出版商:AIP    

年代:1990

数据来源: AIP