摘要:

Raman scattering was used to study optical phonons in a Si12Ge4strained‐layer superlattice onc‐Si(001) that was subjected to hydrostatic pressure at room temperature. The change of phonon frequency with pressure,d&ohgr;/dP, for the principal quasi‐confined LO mode in the Ge layers, is found to be significantly smaller than that for bulk crystalline Ge. This difference is shown to be due to the tuning of biaxial strain in the Ge layers and the pressure response of the confined mode as hydrostatic pressure is varied. Both strain and confinement make comparable contributions tod&ohgr;/dPfor the Ge layers in the superlattice examined here.

ISSN:0003-6951    

DOI:10.1063/1.104894

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The formation and growth of holes and hillocks at grain boundary triple junctions in thin‐film conductors of gold on gallium arsenide and thin‐film conductors of aluminum‐1 wt. % silicon on (oxidized) silicon during the early stages of electromigration have been investigated through measurement of fractional change of electrical resistance &Dgr;R/Rand microstructural characterization by scanning and transmission electron microscopy. Each grain boundary triple junction is characterized by a unique structure factor &Dgr;Y, which defines the degree of cumulative flux divergence and, consequently, the degree of susceptibility to formation and growth of holes or hillocks. Resultant holes are characterized by a shape factor  f, which defines the degree of noncircularity and, consequently, relates fractional change of hole area to &Dgr;R/R. Estimates of the upper limit for &Dgr;Yand the average value of  f  are in good agreement with measured values of &Dgr;R/Rand consistent with observed microstructure.

ISSN:0003-6951    

DOI:10.1063/1.104869

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Mismatched epilayers, for which the coherency strain has been relieved by misfit dislocation introduction, typically exhibit high epithreading dislocation densities. When the misfit is substantial, as for Ge or GaAs grown by molecular beam epitaxy onto (001) Si substrates, the density is regularly over 109cm−2. We have grown Ge on Si (111) and (001) with epithreading dislocation densities in the 106cm−2range by use of chemical vapor deposition. This is because longer, and thus fewer, misfit dislocations appear for strain relief. Potential explanations for this are postulated. The most likely reason is that thermally activated dislocation glide is much faster at chemical vapor deposition growth temperatures.

ISSN:0003-6951    

DOI:10.1063/1.104870

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The structural transformation in self‐ion‐implanted Si has been investigated using Raman spectroscopy and Rutherford backscattering spectrometry. The crystal Si Raman peak at 520 cm−1decreased, broadened, and shifted toward lower wave numbers as the 100 keV Si+dose was increased from 0.8 to 8.5×1014cm−2. These peak shifts can be attributed to uniaxial lattice expansion in the direction normal to the Si surface and they are substantially larger than those predicted in uniaxially strained crystal Si. The results suggest that accumulated defects generated by ion bombardment not only expand the crystal Si lattice but also reduce the force constant which in turn increases plasticity and finally gives rise to amorphization of the Si lattice.

ISSN:0003-6951    

DOI:10.1063/1.104871

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The characteristics of an Al‐Ga top layer on AlGaAs and GaAs surfaces during alternate supply molecular beam epitaxy (MBE) growth are studied byinsituobservation using a MBE scanning electron microscope (SEM) hybrid system. It is found that an Al‐Ga alloy top layer has a pseudo‐self‐limiting nature. It is also found that the migration distance of Al‐Ga atoms on an Al‐Ga alloy top layer is as large as 10 &mgr;m. By utilizing these characteristics, a &mgr;m‐scale Al‐Ga monolayer lateral growth process is realized, and the lateral growth rate, about 1 &mgr;m/s, is observed. Comparison of this growth with migration‐enhanced epitaxy is discussed.

ISSN:0003-6951    

DOI:10.1063/1.104872

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have used the deep level transient spectroscopy signal height as a function of applied stress data and the statistics of the occupancy of theDXcenter to obtain the stress dependence of the thermal binding energy of the neutralDXcenter,EDX. We find thatEDXdecreases with about the same rate for uniaxial stresses along ⟨100⟩ and ⟨111⟩ directions. Our results confirm that theDXcenter is a highly localized center as proposed by Chadi and Chang and disagree with the model assuming theDXcenter being an effective mass state of the doping impurity associated with theLband.

ISSN:0003-6951    

DOI:10.1063/1.104873

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We examine effects of the exchange interaction on the thermalization dynamics of high‐density photogenerated plasmas in quantum wells. A technique for simulating the transient dynamics is presented which combines the conventional Ensemble Monte Carlo method for the carrier‐phonon scattering, with a molecular dynamics scheme for treating the many‐body contributions to the long‐range Coulomb potentials. Account is taken of the exchange‐energy interactions in keeping with the exclusion principle and the Fermi nature of the system. Our results indicate that the exchange corrections slow the cooling of the photogenerated plasma at carrier densities above 1012cm−2. The effect is due primarily to a weakening of the direct Colomb force, and demonstrates that calculations based on simple carrier–carrier scattering alone would underestimate thermalization time constants.

ISSN:0003-6951    

DOI:10.1063/1.105233

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We demonstrated a novel selective growth technology for the fabrication of quantum microstructures utilizinginsitupatterning of contamination resist in the metalorganic chemical vapor deposition system. The results indicate that a GaAs quasi‐quantum wire structure, as narrow as 700 nm, can be successfully fabricated, showing that this technique may be applied to fabrication technologies for quantum microstructures.

ISSN:0003-6951    

DOI:10.1063/1.104874

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on the current‐voltage (IV) characteristics of GaAs/GaN/GaAs semiconductor‐insulator‐semiconductor structures as a function of temperature.IVmeasurements show a strong temperature dependence indicating a thermal distribution of carriers flowing over a barrier. From these data we deduce an effective conduction band barrier of 0.9 eV between GaAs and GaN.

ISSN:0003-6951    

DOI:10.1063/1.104875

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Diethylzinc (DEZn) was used as ap‐type dopant source during metalorganic molecular beam epitaxy of Ga0.47In0.53As and InP. The incorporation efficiency of the Zn was less than 10−3. However, doping levels fromp=1×1017to 3×1019cm−3were obtained at growth temperatures of 485–510 °C. Measurements with secondary‐ion mass spectrometry indicated negligible diffusion of Zn in the Ga0.47In0.53As at these doping levels and growth temperatures. The DEZn was used to dope thep‐type InP cladding layer of broad‐area separate confinement multiquantum well (SCH‐MQW) lasers. Threshold current densities as low as 600 A/cm2were achieved in nonoptimized structures.

ISSN:0003-6951    

DOI:10.1063/1.104876

出版商:AIP    

年代:1991

数据来源: AIP