摘要:

GaAs has been grown on pseudomorphic Si (100) surfaces and (100) surfaces misoriented 4° toward [011] and [001] in order to study the quality of the GaAs on Si interface in the absence of misfit dislocations. We obtain completely two‐dimensional single‐domain GaAs epitaxy after only 80 A˚ of deposition as observed byinsituhigh‐energy electron diffraction. Transmission electron microscopy verifies that the GaAs grown on pseudomorphic Si is free of antiphase domains and other notable defects.

ISSN:0003-6951    

DOI:10.1063/1.102768

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Diffusion of Si in GaAs is studied using implanted Si in undoped GaAs, implanted Si in Se‐, Si‐, and Zn‐doped GaAs, and grown‐in Si in epitaxial layer structures. No diffusion is observed in the undoped and Zn‐doped GaAs cases, a moderate level is observed in the Si‐doped case, and a significant amount is found for the Se‐doped and nonimplanted Si‐doped epitaxy cases. These results indicate that the diffusion is controlled by a Fermi level mechanism (probably via ionized gallium vacancies) and that implant damage inhibits diffusion by keeping the electron concentration and/or the ionized gallium vacancy concentration low.

ISSN:0003-6951    

DOI:10.1063/1.102769

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Electroabsorption of strained‐layer InxGa1−xAs/GaAs superlattice structures grown by molecular beam epitaxy on GaAs substrates was experimentally investigated. Its spectral characteristics were found to be similar to those of Franz–Keldysh electroabsorption of bulk semiconductor materials, and suggest that the widths of ground‐state electron and hole minibands might be larger than the maximum tilt of the potential well caused by an applied voltage. We attribute the electroabsorption of such superlattices to photon‐assisted tunneling between ground‐state electron and heavy hole minibands.

ISSN:0003-6951    

DOI:10.1063/1.102770

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Epitaxial layers of nominally undoped GaAs have been grown by metalorganic chemical vapor deposition using liquid tertiarybutylarsine and triethylgallium.n‐type layers were obtained having total residual shallow acceptor concentrations of ∼1013cm−3and Hall mobilities comparable to those obtained with arsine and triethylgallium in the same reactor. Liquid‐nitrogen Hall mobilities up to 116 000 cm2/V s were observed.

ISSN:0003-6951    

DOI:10.1063/1.102771

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We describe a new method of producing ultrasmall structures on thick substrates with electron beam lithography. Using an innovative exposure technique, we obtain features with lateral sizes smaller than the incident beam diameter. These patterns are transferred into GaAs/AlGaAs quantum well heterostructures using chemically assisted ion beam etching, and uniform arrays of structures with lateral dimensions below 10 nm are produced. We employ reflection electron microscopy measurements to correlate the structure size with the exposure and development conditions for this fabrication scheme.

ISSN:0003-6951    

DOI:10.1063/1.102772

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Low dislocation density (4×105cm−2) GaAs films on Si substrates have been obtained with a GaAs film thickness of 180 &mgr;m using vapor mixing epitaxy based on GaCl‐AsH3(hydride) vapor phase epitaxy for the first time. Dislocation density decreases as the GaAs film thickness increases. Dislocation density is inversely proportional to film thickness in the film thickness region of <10 &mgr;m. However, in the film thickness region >50 &mgr;m (and/or of dislocation density <107cm−2), dislocation density is exponentially proportional to the film thickness. Assuming that this dependence results from a dislocation reaction during GaAs growth, it can be interpreted that the dislocation‐dislocation coalescence reaction mainly occurs with high dislocation density crystals, and additionally, a dislocation annihilation reaction, deflection, occurs with low dislocation density crystals.

ISSN:0003-6951    

DOI:10.1063/1.102773

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The superconducting transition temperatures in Bi2Ca1−xLnxSr2Cu2O8+&dgr;, TlCa1−xLnxSr2Cu2O6+&dgr;, and Tl0.8Ca1−xLnxBa2Cu23O6+&dgr;(Ln=Y or rare earth) vary with composition and show a maximum at a specific value ofxor &dgr;. This observation suggests that an optimal carrier concentration is required to attain maximumTcin such cuprates which seem to be two‐band systems.

ISSN:0003-6951    

DOI:10.1063/1.103296

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Results of growth of InAs on a superconducting TlCaBaCuO (2‐1‐2‐2) thin film are reported. The InAs was grown by molecular beam migration‐enhanced epitaxy at a substrate temperature of 250 °C. TheTc(zero) of the Tl film before and after InAs deposition was 106 and 100 K, respectively. X‐ray diffraction and reflection electron microscopy studies showed the InAs to be polycrystalline, having grains in the 300 A˚ size range. This is the first report of deposition of a III‐V semiconductor on superconductor, without significant degradation ofTc.

ISSN:0003-6951    

DOI:10.1063/1.103297

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

For the Bi‐Pb‐Sr‐Ca‐Cu‐O (BPSCCO) system, a consistent set of data forTc, x‐ray diffraction, and scanning electron microscopy shows that Ag additions strongly react with BPSCCO to destabilize the 110 K superconducting phase, resulting in a strong depression inTcand lattice parameters when samples are treated in air or pure oxygen. This is in contrast to the behavior for the Y‐Ba‐Cu‐O and Bi‐Sr‐Ca‐Cu‐O systems, which do not show such degradation. However, Ag additions show no effects onTcand lattice parameters when samples are treated under low oxygen pressure. The formation of a low‐melting eutectic liquid with Ag2O‐PbO‐CuO solid solution affects the composition of the superconducting phase and degrades superconductivity, while the eutectic may be suppressed by reducing the oxygen partial pressure.

ISSN:0003-6951    

DOI:10.1063/1.103298

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Large arrays of coupled nonlinear oscillators can suffer a noise sensitivity due to competition between huge numbers of coexisting states. We have found direct numerical evidence that a Josephson junction series array can exhibit attractor crowding. Thus, for the parameter values considered, no matter how small the noise level, there is a limit to the size of the array beyond which noise corrupts the in‐phase dynamical state.

ISSN:0003-6951    

DOI:10.1063/1.102774

出版商:AIP    

年代:1990

数据来源: AIP