Effect Of Substrate Orientation Research Articles

The effect of silicon substrate orientation on the formation of Gd-silicide phases

The formation and epitaxy of Gd-silicide compounds were investigated in the solid phase reaction of Gd thin film on (111) and (100) oriented Si substrate by X-ray diffraction, Rutherford backscattering and transmission electron microscopy. It was recognised that the effect of substrate orientation on the phase formation became dominant for Gd films thinner than 30 nm. To determine the role of the substrate orientation on the phase formation, 20 nm Gd films were annealed in-situ under the same conditions for (111) and (100) pairs. At low temperature (320°C for 5 min) the first phase (hexagonal GdSi 2− x ) was formed epitaxially on Si(111), while on Si(100) an amorphous alloy formed. At higher temperatures — 350, 430, 500, 550 and 650°C, and 5 min annealing — epitaxial hexagonal GdSi 2− x was found on Si(111), that could not transform into the second phase (orthorhombic GdSi 2), in contrast to the case, where films were thicker than 30 nm. Meanwhile on Si(100) epitaxial orthorhombic GdSi 2 was found under the same annealing conditions. It was demonstrated, that under a certain thickness (30 nm) the formed phase was determined by the substrate orientation instead of the usual diffusion and reaction processes. Our results show the possibility of amorphous phase formation in GdSi reaction, which is reasonable because of the high mobility difference of the diffusing species.

Ga 溶液 SiLPE における基板面方位の効果 : エピタキシー II

Ga 溶液 SiLPE における基板面方位の効果 : エピタキシー II

Evaluation of composition and growth rate of Ga xIn 1 − xP vapour phase epitaxy

A model has been developed successfully to study the nucleation and growth mechanisms of the Ga x In 1 − x P vapour phase epitaxial (VPE) growth in the Ga-In-HCl-PH 3-H 2 system. Using classical heterogeneous nucleation theory the critical nucleation parameters have been derived and the effect of substrate orientations has been studied. By applying physico-chemical concepts, an expression for the composition has been derived as a function of experimental input parameters by considering the number of intermediate reactions. The effect of experimental input parameters on the nucleation and growth mechanism has been analysed in detail and it was found that the (100) orientation has the highest nucleation barrier, and the composition was strongly affected by deposition temperature and input gas mole ratio. It was also found that Ga is preferentially deposited rather than In. The predicted results are compared with the experimental data and found to be in good agreement.

Effect of substrate orientation on the crystal quality and surface roughness of Nb-doped TiO2 epitaxial films on TiO2

We have grown Nb-doped TiO2 epitaxial films on (100) and (110)-oriented TiO2 rutile substrates by molecular beam epitaxy. Nb substitutionally incorporates at cation sites in the rutile lattice, forming NbxTi1−xO2 solid solutions. However, the crystal quality and surface roughness of the films depend strongly on the substrate orientation. Surface roughening and defect formation occur at lower values of x on (100) than on (110). This result is due to anisotropic changes in the metal-oxygen bond lengths within the rutile structure in going from TiO2 to NbO2; there are 1% and 12% changes in the metal atom to octahedron-base oxygen and metal atom to octahedron-vertex oxygen bond lengths, respectively. Every metal atom in the (100) growth surface has in-plane components of the 12% mismatch. However, only half of the metal atoms in the (110) growth plane have such components. Thus, there is substantially larger in-plane lattice mismatch when the growth surface is (100) compared to (110), resulting in surface roughening and formation of defects at a lower doping level for (100)-oriented NbxTi1−xO2 epitaxial films.

Effect of substrate orientation and crystal anisotropy on the thermally oxidized SiO2/SiC interface

We use the high–low capacitance–voltage technique and the conductance–frequency techniques to characterize the SiO2/SiC interface formed by thermal oxidation of the silicon-face (0001) c-axis, the (112̄0) a-axis, and the (11̄00) a-axis orientations of 6H–SiC. The oxidation rate of the a-axis orientations is 3–5 times higher than that of the silicon face. Interface state densities on the a-axis orientations are a factor of 4–10 times higher than the Si-face c-axis orientation for both n-type and p-type dopings. Maximum oxide electric breakdown fields are about 10–11 MV/cm for both a-axis and c-axis orientations for an oxide thickness of about 60 nm.

Effective mass theory for III-V semiconductors on arbitrary (hkl) surfaces

The effects of arbitrary substrate orientation on the electronic and optical properties of III-V zinc-blende semiconductors are considered. A unitary transformation matrix is used to rotate the 4×4 Luttinger valence band Hamiltonian, and the Bir-Pikus strain Hamiltonian from the conventional (001) surface to any arbitrary (hkl) surface of interest. The effects of strain on several electronic and optical properties are examined. It is found that the strain-induced change in the forbidden gap is largest for the (111) plane and other equivalent planes. Furthermore, the strain is also found to induce both a longitudinal and a transverse piezoelectric field. The longitudinal field reaches a maximum for the (111) surface and its other equivalent planes, while the transverse field reaches a maximum for the (110) surface and its other equivalent planes. The orientation-dependence of the hole effective masses is also examined; it is found that the (111) surface, and other equivalent planes, exhibits the largest heavy-hole mass among all possible planes. Finally, this article examines the effects of orientation on the optical transition matrix elements. For incident light with in-plane polarization vectors, the matrix elements are, in general, anisotropic—with the largest anisotropies predicted for two new surfaces: the (√310) and the (1√30) surface.

A Self-Organized Molecular Beam Epitaxial Growth of the InSb/AlGaSb Quantum Dots on High-Index GaAs Substrates

AbstractIn-situ organization of InSb quantum dots on Al0.5Ga0.5Sb is reported. Samples were grown on just (100), 5°off (100) towards [0-1-1],(311)A, and (311)B surfaces of GaAs by molecular beam epitaxy. The growth mechanism and characteristics of quantum dots were analyzed using reflection high-energy electron diffraction, atomic force microscopy, and photoluminescence. Observed photoluminescence peak shift towards lower energy side with InSb thickness was interpreted by the development of quantum dots. Substrate orientation effect was examined and found to be useful to increase the dot density. As a result, as high as ~3xl 09 cm-2 dot density was achieved on the (311 )B substrate whereas the typical value on the (100) was ~2xl 08 cm-2 .

Surface Morphology of Ingap in the Ai-Free Pump Ld

AbstractWe have studied the effects of growth parameters and substrate orientations on InGaP quality using Normarski microscopy, photoluminescence (PL) spectrum and atomic force microscopy (AFM). The full width at half maximum (FWHNM) and peak position of PL spectrum were closely related with the surface morphology. The InGaP layers of narrower FWHM and shorter peak wavelength had smoother surface morphology. The InGaP layers grown on (100) substrates at the moderately low reactor pressure showed rougher surface than those on the tilted substrates. But the surface morphology was noticeably improved to be mirror-like at the lower reactor pressure. The surface morphology was inverted between the exact and tilted substrates in this reactor pressure. Furthermore, the samples grown on the tilted substrate exhibited rougher surface than the samples grown on the exact substrate. (111)B-misoriented growth surfaces had smoother than (111)A-misoriented surfaces.

Chemical and Electrochemical Heteroepitaxial Growth of Chalcogenide Semiconductors from Solutions

ABSTRACTChalcogenide semiconductors have been deposited epitaxially from aqueous solutions either chemically or electrochemically at growth rates of up to 0.7 μmhr−1. After recalling the basic principles of these deposition processes, results are presented concerning chemically deposited CdS on InP, GaP and CuInSe2 substrates, electrodeposited CdTe on InP, and CdSAnP heterostructures. Characterisation of these structures by RHEED, TEM, HRTEM, and glazing angle X ray diffraction allows to analyse the effects of substrate orientation, polarity, lattice match plus the influence of temperature on epitaxial growth. These results are discussed in terms of self organisation and a site selective growth mechanisms due to the free enegy of formation of each compound.

Substrate orientation dependence of low-temperature GaAs grown by molecular beam epitaxy

A systematic study of the substrate orientation effect on crystalline quality of GaAs grown by molecular beam epitaxy at low substrate temperature (215 °C) was performed using double-crystal x-ray diffractometer and transmission electron microscopy. The crystal quality was found to be strongly correlated with substrate orientations. Layers of high crystalline perfection with excess arsenic were obtained on both GaAs(100) and (311)B substrates, while columnar polycrystalline growth was observed on (211)B substrate. The transition from a single crystalline state to a polycrystalline state was clearly demonstrated by a 0.5 μm GaAs layer on (111)B surface. Surface kinetic factors are believed to play important roles during the low temperature growth.

The effect of substrate orientation on WSi2 formation

Abstract The effect of substrate orientation on tungsten silicide formation has been studied. It has been found that the silicide on Si(100) forms at low temperature, has fine grained surface morphology and has low sheet resistance as compared with that formed on Si(111). We attribute this to the difference in microstructure of the films, due mainly to the difference in the nucleation process for the two substrates.

Homogeneity of Wet Oxidation by RTP

ABSTRACTThe implementation of a wet oxidation process in an RTP system using a bubbler with deionized water is described. A special process related calibration in a wet atmosphere, by means of pyrometer and thermocouple readings, allows one to improve the temperature accuracy during the oxidation to an offset of only + 1 to 2°C. High oxide growth rates, up to a factor of 1.8 above literature data have been achieved. Wet and dry RTO oxides are compared and related to the expectations from growth models. Effects of growth time (10 s to 4 min), growth temperature (675°C-950°C), substrate orientation (100,111), preparation (e.g. HF) and bubbler temperature (20°C-90°C) are presented. The uniformity of oxides on 4 and 6 inch diameter wafers are discussed. Preferentially by the use of a silicon guard ring and by adjusting lamp power and gas flow rates excellent results concerning uniformity (standard deviations 2σ: 1-2 %) and reproducibility (variation of 0.5 to 0.75 % at least over 12 wafers) are obtained.

Effects of substrate orientation and cooling rate on microstructure of PbTiO 3 thin films grown by metal-organic chemical vapor deposition

PbTiO 3 thin films grown on (001) MgO, (110) MgO and (111)-textured Au/(001)MgO by metal-organic chemical vapor deposition have been characterized by X-ray diffraction, transmission electron microscopy and high resolution electron microscopy. PbTiO 3 films deposited on (001) MgO under optimum conditions show a bilayer structure. The top layer of the films near the free surface is c axis oriented with (001)[100]PbTiO 3 ‖ (001)[100]MgO. The bottom layer of the films near the substrate is a axis oriented with (100)[00 1 ]PbTiO 3 ‖ (001)[100]MgO. 90° domains (or {101} twins) were observed only in the c-axis-oriented layers. The thickness of the a-axis-oriented layers depends on the cooling rate and film thickness. It was found that the thickness of the a-axis-oriented layers near the substrate decreases with decreasing cooling rate and/or increasing film thickness. PbTiO 3 films deposited on (110) MgO, however, are single-layer epitaxial thin films with (101)[001]PbTiO 3 ‖ (110)[001]MgO. Highly (001)-textured PbTiO 3 thin films were obtained on (111)-oriented Au/(001)MgO. This texture appears to be due to a number of small holes (<1 μm) formed in the Au thin films during heating to the growth temperature. These holes seem to have acted as nucleation sites for (001) PbTiO 3 on (001) MgO. Since the growth rate along {100} is much faster than along other directions for PbTiO 3, the resultant films are highly c axis oriented.

Si/SiGe modulation-doped structures with thin buffer layers: Effect of substrate orientation

High quality Si (strained)/Si0.7Ge0.3 (relaxed) modulation-doped structures incorporating unusually thin (700 nm) buffer layers were grown with molecular beam epitaxy at 700 °C. By utilizing (100) substrates misoriented toward (011) by 4°, the density of threading dislocations was reduced by over an order of magnitude as compared with conventional techniques. These layers produced exceptionally high Hall mobilities of 1790 cm2/V s at 300 K and 19 000 cm2/V s at 77 K on n-type modulation-doped heterostructures. The effect of substrate misorientation on threading dislocation density was investigated using transmission electron microscopy and Nomarski microscopy.

Molecular dynamics simulations of thin film growth on Ag(100) and (111) with energetic Ag atoms

Molecular dynamics simulations of the deposition of atoms on crystalline surfaces have been conducted using the embedded atom method. These simulations studied 0.1–40 eV Ag atoms deposited on (111) and (100) Ag substrates. The purpose of the calculations for Ag atoms deposited on Ag substrates was to investigate the effects of adatom arrival energy and substrate orientation on the interactions of low-energy atoms with crystal surfaces. For the Ag at 0.1 eV, representative of thermal evaporation, the degree of island formation on (111) and the (100) substrates was similar. At a given atom arrival energy between 10 and 40 eV, both the redistribution into full monolayers and the mixing by surface exchange interactions were seen to occur more readily on the close-packed (111) growth surface than on the more open (100) surface.

Substrate orientation effects on dopant incorporation in InP grown by metalorganic chemical vapor deposition

We have investigated the doping incorporation and activation of InP growth using metalorganic chemical vapor deposition on &amp;lt;100≳, &amp;lt;311≳B, and &amp;lt;110≳ InP substrates. Effects of orientation, growth temperature, and V/III fluxes were studied. The dopants used were Zn from dimethylzinc [(CH3)2Zn] and diethylzinc [(C2H5)2Zn], S from hydrogen sulfide [H2S], Si from silane [SiH4], and Sn from tetraethyltin [(C2H5)4Sn]. The incorporation and activation of the p-type dopant Zn are elevated on the &amp;lt;311≳B and &amp;lt;110≳ planes, while the incorporation is suppressed for the n-type dopants (S, Si, and Sn). The n-type dopant Sn has similar incorporation and activation on the various substrate orientations studied. Anomalous Zn doping on the higher order planes &amp;lt;311≳B and &amp;lt;110≳ lead to the Zn incorporation exceeding the solubility limit in InP. Incorporated Zn levels as high as 1.0×1019 cm−3 were measured, and the corresponding activated Zn level was as high as 5.4×1018 cm−3 on a &amp;lt;110≳ InP substrate. Interdiffusion of the p-type dopant Zn into the S-doped n-type InP substrate is inhibited by a high S-doping level and segregates at the substrate–epilayer interface. If the S-doping level is lower than the Zn concentration, then Zn diffuses deep into the substrate at a uniform level.

Cyclotron resonance measurements of the hole mass in [0 0 1] and [1 1 1] In xGa 1− xSb/GaSb quantum wells

Cyclotron resonance has been employed to explore the effects of substrate orientation and carrier concentration on the valence band structure of strained In x Ga 1− x Sb/GaSb quantum wells. The in-plane masses are much reduced by the strain decoupling of the heavy-hole and light-hole levels. We find that the in-plane mass is lower for [1 1 1] growth than for [0 0 1] growth, which we relate to the fact that γ 3>γ 2 (Luttinger parameters). [1 1 1] samples were grown with high carrier concentrations (∼5×10 11 cm −2) by exploiting the modifications to the band profile induced by the piezoelectric field. For filling factors v<3 we observe two cyclotron resonance lines, with masses differing by up to ∼40%, corresponding to heavy-hole transitions with opposite spin, M J=± 3 2 . The results show that the first M J=± 3 2 levels are more strongly coupled to the light-hole states than the first M J=- 3 2 levels. This behaviour is verified by k · p theory calculations of the Landau levels.

Effects of Growth Conditions and Substrate Orientation on the Properties of InSb

AbstractTwo new organometallic Sb sources, tris(dimethylamino)antimony (TDMASb), and tertiarybutyldimethylantimony (TBDMSb) are being investigated. The growth of InSb using TDMASb, or TBDMSb and TMIn was investigated over a temperature range of 350 to 475 °C using a range of V/III ratios, growth rates and pressures. Misoriented InSb substrates were also used for selected growth conditions The growth rates of lnSb using TMIn and either TDMASb or TBDMSb at temperatures &lt;= 425 °C were proportional to both the TMIn flow rate and the temperature. The surface morphology of InSb grown using either TDMASb or TBDMSb was very rough for growth temperatures &lt;=425 °C. This may be due to the complex decomposition mechanisms involved and the presence of methyl groups on the surface. Smoother backgrounds were generally found when using off axis substrates. The details of the defects observed on the surfaces were dependent on the type of misorientation and can be related to the atomic structure of the surface steps. Both n- and p-type InSb were grown using TBDMSb or TDMASb and TMIn with mobilities up to 68,990 and 7773 cm2/Vs, respectively, at 77 K. The mobility for lnSb using either TDMASb or TBDMSb was optimized by going to lower temperatures, pressures and V/III ratios. The opposite was true for surface morphology which improved with higher temperature, pressure, and V/III ratio. The growth of high mobility InSb with smooth surfaces at T&lt; =425 °C was not achieved with TDMASb or TBDMSb and TMIn under the conditions investigated in this work.

Substrate Doping and Orientation Effects on Dielectric Growth on Siucon in a Nitrous Oxide Environment

ABSTRACTIn this paper both the substrate doping concentration and single crystal silicon orientation are considered when dielectrics are grown on silicon in a nitrous oxide environment. Our initial preliminary findings show that for heavily doped subtrates thicker layers of dielectric result compared to their lower doped counterparts. Furthermore we find a crossover point of temperature for growth rate for &lt;111&gt; compared to &lt;100&gt;. We believe that the different growth rates are attributable to nitrogen build up at the dielectric interface.

Alloy clustering and defect structure in the molecular beam epitaxy of In0.53Ga0.47As on silicon

The MBE growth of InxGa1−xAs (x ∼ 0.53) on silicon substrates has been investigated emphasizing the effects of substrate orientation and buffer layers between In0.53Ga0.47As and Si. It is shown that growth on silicon substrates misoriented from (001) toward a [110] direction eliminates the presence of antiphase domains. The best In0.53Ga0.47As surface morphology was obtained when a 0.9 μm epitaxial Si buffer was initially grown, followed by a pre-exposure of the silicon surface to As4 at 350 °C, followed by the growth of In0.53Ga0.47As. Threading dislocations, stacking faults, low-angle grain boundaries, and spinodal decomposition were observed by TEM in the InGaAs layers. The spinodal contrast scale was shown to depend on the buffer type and the total InGaAs thickness. Thick buffers consisted of GaAs or graded InxGa1−xAs layers, and large In0.53Ga0.47As thicknesses favor the development of a coarse-scale spinodal decomposition with periodicity around 0.1 μm. Thin GaAs buffers or direct In0.53Ga0.47As growth on Si may result in a fine-scale decomposition of periodicity ∼10 nm. The principal strain direction of the spinodal decomposition appeared along the [1$\overline 1$0] direction, parallel to the vicinal Si surface step edges. InGaAs immiscibility affects the InGaAs growth process, favoring a 3-D growth mode. X-ray diffraction measurements and photoreflectance spectra indicated that the sample quality was improved for samples exhibiting a fine-scale spinodal decomposition contrast even if they contained a higher dislocation density. Threading dislocations run almost parallel to the [001] growth axis and are not affected by strained layers and short period (InAs)3/(GaAs)3 superlattices. The lowest double crystal diffractometry FWHM for the (004) InGaAs reflection was 720 arc sec and has been obtained growing InGaAs directly on Si, while the lowest dislocation density was 3 × 109 cm−2 and was obtained using a 1.5 μm GaAs buffer before the In0.53Ga0.47As deposition.