摘要:

Xe ion irradiation of polycrystalline silicon before Ti deposition is found to affect subsequent silicide formation. Silicide films were prepared by implanting 60, 100, or 240 keV Xe+ions into 500‐nm‐thick undoped polycrystalline silicon before depositing Ti and annealing in vacuum. Preimplantation altered the subsequent silicide resistivity, x‐ray diffraction patterns, and morphology as compared to films prepared on unimplanted polycrystalline Si substrates. We found that minimal TiSi2resistivities were achieved at lower temperatures with preimplantation, indicating that the Xe‐implanted substrate promotes a lower temperature transition from the metastable C49 phase to the low‐resistivity equilibrium C54 phase of TiSi2. X‐ray diffraction results confirmed the lower temperature formation of the C54 phase with preimplantation. Low‐temperature annealing (650 °C, 30 min) of 6×1016cm−2, 240 keV Xe+‐implanted samples yielded low‐resistivity (∼22 &mgr;&OHgr; cm) silicide films, while simultaneously annealed samples without preimplantation had resistivity five times higher. Lower doses were effective at lower implant energies, with low resistivity achieved after 725 °C, 30 min annealing for 2×1015cm−2, 60 keV Xe+preimplantation.

ISSN:0003-6951    

DOI:10.1063/1.103295

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Satellite peaks analogous to superlattice peaks have been observed for both corrugated InP substrates and for such substrates overgrown with epitaxial InGaAsP. These satellites are entirely due to the corrugations. High-resolution x-ray diffraction using extremely asymmetric reflections in the glancing exit configuration was used. A kinematical expression for the intensities of the satellite peaks is derived for strain-free structures.

ISSN:0003-6951    

DOI:10.1063/1.102759

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

For the first time the observation of a sharp peak in the broad luminescence spectrum of hydrogenated amorphous silicon (a‐Si:H) has been achieved, using erbium as a dopant. Thus, a method of investigating the structure of solid‐state systems which previously has only been used with crystals can now be applied toa‐Si:H. The idea is to measure the splitting of the luminescence of ‘‘spy’’ atoms, or ions, by the crystal field of the host substance subject of investigation into which they are incorporated. Finding a suitable substance for use witha‐Si:H has proven to be a difficult task, which we now have accomplished as a first step in establishing this method for the investigation of amorphous substances.

ISSN:0003-6951    

DOI:10.1063/1.102760

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin films of GaAs on Si were grown by molecular beam epitaxy, which involves the solid phase epitaxial (SPE) growth of the amorphous GaAs buffer layer. A Rutherford backscattering minimum channeling yield of ∼9.4% has been obtained for a 0.8‐&mgr;m‐thick GaAs film. Cross‐sectional transmission electron micrographs and reflection high‐energy electron diffraction results have revealed that misfit dislocations are mostly confined to what used to be the buffer layer of ∼300 nm in thickness, and that the microtwins (and/or stacking faults) are mostly originated from the GaAs/Si interface and are generated during SPE growth.

ISSN:0003-6951    

DOI:10.1063/1.102761

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thermally stimulated desorption and x‐ray photoelectron spectroscopy were used to study the air oxidation at room temperature of HF‐treated Si(100) surfaces. The desorption results indicated an appreciable density of hydrogen at the surface. Air oxidation experiments with predesorbing surface hydrogen were carried out and an obtained linear relationship between the amount of H2desorption and oxidation indicated that the oxidation was allowed by H2desorption. The surface hydrogen was also found to be stable in air at room temperature and to contribute to a retardation in air oxidation of the surface.

ISSN:0003-6951    

DOI:10.1063/1.102762

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Remotely doped parabolic quantum wells have been used to produce thick (>2000 A˚) layers of high‐mobility electron systems. Using a front gate electrode we are able to simultaneously deplete the well and change the actual thickness of this quasi‐three‐dimensional system. Thus, we can successively depopulate the elecrical subbands in the well, leading to step‐like changes in the gate to channel capacitance. This yields direct insight into the subband structure of the electron system and allows its spectroscopy without the need of a magnetic field. The experimental results are compared with those of a self‐consistent subband calculation and we obtain a qualitative agreement.

ISSN:0003-6951    

DOI:10.1063/1.102763

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The formation of amorphous interlayers (ainterlayers) in polycrystalline Zr and Hf thin films on single‐crystal (111)Si has been observed by cross‐sectional transmission electron microscopy. The growth ofainterlayers in group IVa metal thin films on silicon was found to exhibit similar behavior but was fundamentally different from those of metal‐metal diffusion couples. The growth ofainterlayers was found to follow a linear growth law initially then slowed down until a critical thickness was reached. Si was found to be the dominant diffusing species. Good correlation was found among the maximum thickness of theainterlayer, the difference in atomic size between metal and Si, the activation energy of the linear growth, and the largest heats of formation of the respective silicides.

ISSN:0003-6951    

DOI:10.1063/1.102764

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The critical thickness for Si1−xGexstrained layers for the alloy range 0<x<0.15 has been determined from annealed epilayers using mapping techniques which allow single dislocation detection and composition thickness measurements over large areas (∼50 cm2). A series of Si1−xGexlayers was deposited by molecular beam epitaxy in which the composition (x) and thickness (h) were continuously varied across the substrate to produce a slowly changing strain energy density through the stable/metastable transition. On annealing at either 750 or 900 °C for 30 min, an abrupt transition in relaxation behavior was found at critical values of thickness and composition (hc,xc). Increasing the anneal temperature or time did not shift the transition giving identical (hc,xc) values. At strain thicknesses above these critical values a large increase in defect density was observed (>∼104, cm−2) whereas in thinner strained epilayers, below the thermodynamic stability curve, no misfit dislocations were found. Nomarski microscopy of defect etched surfaces and x‐ray topography were used to reveal misfit dislocations formed during the initial stages of relaxation. The appearance of single misfit dislocations at a density ≊1 cm−2was taken as the criterion for a ‘‘relaxed’’ layer. The critical strain and thickness in the vicinity of these transition points were determined on the as‐grown wafer by x‐ray diffraction and Rutherford backscattering spectrometry with confirmation of layer thicknesses by cross‐sectional transmission electron microscopy. The Matthews–Blakeslee [J. Cryst. Growth27, 118 (1974)] equilibrium critical thicknesshe(nm), vs Ge atom fraction curve given byxe=0.55/he ln(4he/b) for 1/2a0⟨110⟩, 60° glide dislocations with a Burgers vectorb∼0.4 nm, is an excellent fit to these experimental data, i.e.,xc=xeandhc=he.

ISSN:0003-6951    

DOI:10.1063/1.102765

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Dual implantations of 150 keV Si+ions and 160 keV P+ions with the same dose of 1×1015/ cm2were performed at 200 °C. Si3N4encapsulated samples were annealed in a conventional furnace or a halogen tungsten lamp rapid thermal annealing system. The carrier concentration profiles show that the Si dopant is highly activated and its indiffusion is effectively reduced with the help of P+implantation and rapid thermal annealing. The highest carrier concentration of 5×1019/cm3, corresponding to an activation of 70%, an average electron mobility of 750 cm2/V s, and a sheet resistance of 11 &OHgr;/&laplac;, has been obtained in Si+and P+dually implanted InP after rapid thermal annealing at 850 °C for 5 s.

ISSN:0003-6951    

DOI:10.1063/1.102766

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

By evaporating gallium from an aluminum‐treatedpBN crucible in a molecular beam epitaxy (MBE) system, ‘‘Ga spitting’’ and formation of Ga cell related oval defects have been eliminated. MBE GaAs layers as thick as 20 &mgr;m were totally free from the Ga cell related oval defects. Remaining defects were particulates or oval defects related to surface contamination and their densities were 100 and 500 cm−2for 5 and 20‐&mgr;m‐thick layers of GaAs. The particulates‐related oval defects were, however, hardly seen when 4‐&mgr;m‐thick GaAs was grown on Si substrates. Aluminum wets and reacts with thepBN crucible when heated to 1300 °C. Condensed gallium near the orifice wets the aluminum‐treated surface. As a result, Ga droplets and related oval defects do not form. The method also avoids any gallium oxide in the Ga melt and provides a better outgassedpBN crucible. Contamination of the initial GaAs layers with Al was negligibly small with Al contentx=0.0016 which reduced in subsequent layers. The results are presented for GaAs layers but the method should be equally applicable for evaporation of indium to prevent In‐related oval defects in In‐based compounds.

ISSN:0003-6951    

DOI:10.1063/1.102767

出版商:AIP    

年代:1990

数据来源: AIP