摘要:

A thermodynamic formalism is developed for illuminating the predominant point defect mechanism of self- and impurity diffusion in silicon and is used to provide a rigorous basis for point defect-based interpretation of diffusion experiments in biaxially strained epitaxial layers in the Si–Ge system. A specific combination of the hydrostatic and biaxial stress dependences of the diffusivity is±1times the atomic volume, depending upon whether the predominant mechanism involves vacancies or interstitials. Experimental results for Sb diffusion in biaxially strained Si–Ge films andab initiocalculations of the activation volume for Sb diffusion by a vacancy mechanism are in quantitative agreement with no free parameters. Key parameters are identified that must be measured or calculated for a quantitative test of interstitial-based mechanisms. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119066

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate the growth of a relaxed, only 1 &mgr;m thick, stepwise graded buffer based on a combination ofSi1−xGexandSi1−x−yGexCy.This buffer concept relies on the retardation of dislocation glide inSi1−x−yGexCyrelative to strain equivalentSi1−xGexon silicon. The homogeneousSi1−xGexlayer withx=30&percent;on top of the buffer structure is(73±5)&percent;relaxed. For the nonoptimized buffer growth, we already find a threading dislocation density below105 cm−2.A steppedSi1−xGexbuffer with the identical thickness and strain profile grown with the same temperature ramp yields a threading dislocation density above107 cm−2.This indicates that the addition of carbon is a promising way for new relaxed buffer concepts with low threading dislocation densities. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119067

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Biaxially aligned cerium oxide(CeO2)and yttria stabilized zirconia (YSZ) films were deposited on Ni-based metal (Hastelloy C276) substrates held at room temperature using ion beam assisted (IBAD) magnetron deposition with the ion beam directed at 55° to the normal of the film plane. In addition, we achieved, room-temperature epitaxial growth ofCeO2by bias sputtering to form biaxially alignedCeO2/YSZbilayers. The crystalline structure and in-plane orientation of films was investigated by x-ray diffraction techniques. Both the IBADCeO2and YSZ films, and theCeO2/YSZbilayers have a (111) pole in the ion beam direction. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119017

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate that di- and monohydride desorption peak temperatures are shifted lower for boron-doped films and higher for phosphorus-doped films compared to intrinsic Si(100). This observation is exploited to show that the shifts in di- and monohydride desorption peak temperatures with doping are accompanied by shifts in the growth mode transition temperatures, with one exception which is discussed. This work suggests that dihydrides lead to breakdown of epitaxial growth while monohydrides promote three-dimensional epitaxial growth. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119207

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optical spectra of the bulk three-dimensional InGaN alloys were measured using the commercially available light-emitting diode devices and their wafers. The emission from undopedInxGa1−xN(x<0.1)was assigned to the recombination of excitons localized at the potential minima originating from the large compositional fluctuation. The emission from heavily impurity-doped InGaN was also pointed out related to the localized states. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119013

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have experimentally observed a new kind of current bistability in the time-averaged current-voltage (I-V) characteristic of doped, weakly coupled GaAs/AlAs superlattices, in which the transport is dominated by sequential resonant tunneling between adjacent quantum wells. Time-resolved current measurements show that in some cases the bistability is correlated with a subcritical Hopf bifurcation, while in other cases a discontinuous change of the current oscillation frequency is observed in the bistable region. The origin of this new bistability is attributed to a change of the space charge layer in the superlattice involving charging and discharging effects, which creates a feedback to the external bias. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119014

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new fabrication process to create InGaAs/InP quantum wires on (100) GaAs substrates is demonstrated. The process is based on the selectivity of the growth of InP on lines created by focused ion beam bombardment, together with the selectivity of the growth of InGaAs on the InP wires. Intense photoluminescene is observed from the wires and the emission shows clear polarization parallel and perpendicular to the wires. Cathodoluminescene images confirm that the luminescence originates from the wires. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119015

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We describe epitaxial growth of solid solutions ofGaAs1−xNxwith high nitrogen concentrations. The equilibrium constants of reactions needed for the formation of single phase alloys are calculated and compared with experimental pressure and growth temperature data. We show good agreement between the experiment and the calculated thermodynamic growth conditions. In addition, our calculations indicate that at room temperature the alloys ofGaAs1−xNxare either unstable or metastable with respect to decomposition, for the entire range of compositions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119016

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A full theory of thermoelectric transport in superlattices, including the well width and energy dependence of the optical and acoustic phonon scattering and the effects of confinement in raising valley degeneracy is developed. It is shown that these features result in qualitatively significant modifications in the predicted figure of merit of superlattice systems. Results are given for PbTe superlattices, and comments are made on recent experimental results for such systems. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119018

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report a photoluminescence (PL) study ofSi1−xGex/Sisurface quantum wells (SFQWs). The PL peak energies are found to be affected by strain relaxation in Ge-rich SFQWs while a PL energy lowering was observed forx⩽0.47as compared to buried quantum wells capped with Si. Exciton localization in the lateral direction is suggested to be the dominant PL mechanism in SFQWs rather than perpendicular confinement effects that are expected for SFQWs. PL degradation and a spectral dominance switch over to newly developing lower energy peaks were clearly observed after prolonged air exposure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119019

出版商:AIP    

年代:1997

数据来源: AIP