摘要:

Deep levels in GaAs on Si substrates grown by metalorganic chemical vapor deposition (MOCVD) were studied during infrared rapid thermal annealing. For GaAs layers on Si after annealing at 850 °C for 20 s, three electron deep levels at 0.36, 0.27, and 0.20 eV below the conduction band were created as the dominant deep levels. Especially, the 0.36 eV level was found to increase up to 40% of the donor concentration as the thickness of Si substrates increased. These results indicate that rapid thermal annealing of GaAs on Si may induce high‐density deep levels due to a biaxial tensile stress caused by the difference in thermal expansion coefficients.

ISSN:0003-6951    

DOI:10.1063/1.102705

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Photoluminescence at the photon energies of 0.808 and 0.874 eV was observed in silicon containing a high concentration of carbon after a two‐step isochronal anneal. The annealing sequence consisted of a low‐temperature isochronal anneal and a 1050 °C anneal, respectively. The observed luminescence had the photon energies corresponding to those of theDlines which are known to arise from the interstitial‐type dislocation loops. In silicon containing a high concentration of carbon, a formation of the dislocation loops was hypothesized to occur via a condensation of the excess silicon interstitials, originated from the agglomerates of interstitial carbons.

ISSN:0003-6951    

DOI:10.1063/1.102707

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have identified symmetrically strained Si‐Si1−xGexsuperlattices with optimum strength infrared spectra in the range 50–300 meV. The growth structure parameters required for implementing such systems are provided.

ISSN:0003-6951    

DOI:10.1063/1.102708

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Medium wavelength infrared (MWIR) detectors in the 3–5 &mgr;m band are demonstrated using bound to continuum state intersubband absorption in lattice‐matched InGaAs/InAlAs multiquantum well (MQW) structures. Photodetectors with responsivity peaked at 4 &mgr;m wavelength showed low dark current giving a background‐limited detectivityD@B|BL=2.3×1010cm(Hz)1/2/W at temperatures up to 120 K.

ISSN:0003-6951    

DOI:10.1063/1.103186

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A study of the impact of semiconductor superlattices on millimeter wave nonlinearities is reported. &khgr;(3)as large as 10−2esu can be achieved by using 250 GHz radiation. Self‐induced transparency is also predicted, and its competition with the third‐harmonic generation process is quantified.

ISSN:0003-6951    

DOI:10.1063/1.102709

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report cathodoluminescence (CL) imaging and transmission electron microscopy (TEM) studies of patterned GaAs/AlAs quantum well (QW) heterostructures grown by molecular beam epitaxy on periodically corrugated substrates. Faceting and surface diffusion during crystal growth result in significant lateral variations in QW thickness which translate quantum size effects into lateral band‐gap patterning. The CL images directly display lateral periodic modulation in quantum well thickness and indicate the existence of two lateral potential wells formed at the bottom and apex of corrugations. Emission wavelengths are in agreement with TEM data on the patterned structures. Such periodic patterned QW heterostructures should be useful for the realization of arrayed one‐ and zero‐dimensional semiconductor quantum structures, particularly lateral superlattice heterostructures.

ISSN:0003-6951    

DOI:10.1063/1.102684

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The crystal structure and superconducting properties of the Bi‐Pb‐Sr‐Ca‐Cu‐O system with Ca‐ and Cu‐rich nominal composition were investigated. A nearly single‐phased 110 K highTcsuperconductor can be obtained with 852 °C/20 h sintering from the starting composition of Bi1.7Pb0.4Sr1.6Ca2.4Cu3.6Oy. X‐ray diffraction patterns, resistivity measurement, diamagnetic susceptibility results, and scanning electron micrographs all indicate that the Ca‐ and Cu‐rich nominal composition would result in better superconducting properties than those of Ca:Sr=1:1 Bi‐Pb‐Sr‐Ca‐Cu‐O compounds in a much shorter sintering time.

ISSN:0003-6951    

DOI:10.1063/1.103315

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin, superconducting Tl‐Ba‐Ca‐Cu‐O films were grown using a two‐step fabrication process which involved the growth of Ba‐Ca‐Cu‐O films by reactive magnetron sputtering followed byexsituhigh‐temperature crystallization and thallination under thallium oxide vapors. Films were thallinated with both Tl2O3and Tl2Ba2CuO6as the source for thallium oxide vapors. Highly oriented films were obtained with thecaxis perpendicular to the surface of the film. Best films had aTc(R=0) of 104 K and a critical current density of 5×104A/cm2at 77 K.

ISSN:0003-6951    

DOI:10.1063/1.103316

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Epitaxial YBa2Cu3O7films were grown on Al2O3 {1¯012} by a laser ablation technique. X‐ray diffraction shows that films are epitaxial with thecaxis perpendicular to the substrate surface and ‘‘123’’ [110] aligned with sapphire [101¯1], although the full width at half maximum of the rocking curve is larger than those of epitaxial films on SrTiO3. TypicalTc’s are between 85 and 88 K with transition widths between 0.5 and 3 K. The normal‐state resistivity is 270 &mgr;&OHgr; cm at 300 K and extrapolates to zero at zero temperature while the magnetizationJcis as high as 5×106A/cm2at 4.2 K. High‐frequency loss measurements show that 2000‐A˚‐thick epitaxial films on Al2O3 {1¯012} have a surface impedance about 1 m&OHgr; at 13 GHz at 4.2 K.

ISSN:0003-6951    

DOI:10.1063/1.103317

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Low‐leakage, thin‐film planar tunnel junctions made of Y1Ba2Cu3O7−x/ native barrier/Pb were fabricated. The Y1Ba2Cu3O7−xfilms were prepared byinsitumolecular beam epitaxy aided with an activated oxygen source. The as‐grown, smooth superconducting perovskite film surface exhibits quasi‐particle tunneling characteristics very similar to the etched bulk single‐crystal data. The results in agreement are a linear dependence of the normal‐state conductance on voltage, a gap‐like structure at ∼20 mV, asymmetric modulations up to 50 mV, and a finite zero‐bias conductance at low temperature. Junctions of lower resistance show, at temperatures belowTcof Pb, the development of a supercurrent at zero bias and associated hysteretic subgap structure, with a typicalIcR∼0.5 mV. Josephson‐like behavior occurred in response to applied magnetic field and microwaves.

ISSN:0003-6951    

DOI:10.1063/1.103318

出版商:AIP    

年代:1990

数据来源: AIP