摘要:

Si epitaxy is strongly affected by the presence of an adsorbate (surfactant). We have examined both film quality and dopant incorporation in homoepitaxy for Sb, As, and Ga terminated Si(111). The efficency of site exchange between Si and adsorbate depends sensitively on binding energy and binding geometry of the adsorbate. For a weakly bound adsorbate (Ga or Sb), there is no inhibition of epitaxy, but a strongly bound adsorbate (As) kinetically inhibits growth. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114065

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report high resolution (<0.05 cm−1) photoluminescence (PL) spectra of erbium implanted float‐zone (FZ) and Czochralski grown (CZ) silicon. We show that the PL spectrum of cubic Er centers observed in CZ‐Si annealed at 900°C is the dominant emission in FZ‐Si for the same annealing conditions. We assign it to isolated, interstitial erbium. We observe also two other kinds of optically active Er centers with lower than cubic site symmetry: (i) O‐related (found only in CZ Si) and (ii) those related to radiation defects. We conclude that coimplantation with light elements does not lead to the formation of Er‐codopant complexes, but rather to Er forming complexes with implantation induced lattice defects. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114066

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Excitation and relaxation mechanisms of Yb3+ions in InP and InP0.93As0.07alloy have been studied based on optically detected cyclotron resonance (ODCR), temperature dependent photoluminescence (PL), and PL decay measurements. It is shown with use of ODCR that charge carriers, most probably electrons, are captured by Yb3+ions. PL transients show that the decay rate of the Yb3+PL decreases with increasing As contents. Evidence is presented proving that the excited state of the Yb3+ion decays by transfer of energy to the band states of InP, while in the case of InPAs, the energy may also be transferred to an exciton bound at the Yb3+ion. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114067

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Si(111) surface treated with HF solution was studied using Fourier transform infrared reflection absorption spectroscopy for the observation of Si–Fxbond absorption and x‐ray photoelectron spectroscopy for the identification of the adsorbates on the Si surface. Two absorption peaks were observed in the range of 905–925 cm−1, and they were assigned to Si–F2symmetric stretching mode at 918 cm−1and Si–H2bending mode at 910 cm−1. The absorption peak of Si–F2distinctly decreased with de‐ionized water rinse, though the Si–H2peak hardly changed. The absorption peak of Si–F was not observed in all spectra. This result indicates that F atoms selectively adsorbed at a step region rather than on a terrace region on Si(111) surface after HF treatment. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114068

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Misfit dislocation arrays in In0.2Ga0.8As epilayers grown on GaAs substrates tilted 2°–10° away from exact (001) toward varied directions have been studied by transmission electron microscopy. A method has been developed to determine the glide plane and the Burgers vector of each misfit dislocation in the tilted InGaAs/GaAs interfaces. Based on experimental observations and theoretical analyses, it is proposed that a stacking fault surrounded by a 30° partial is at first generated by a growth error, followed by thermally activated nucleation of a 90° partial dislocation that removes the stacking fault and forms a 60° dislocation. From the frequency of nucleation events versus the dislocation glide force, the energy barrier for dislocation nucleation of &agr; and &bgr; 90° partial dislocations was determined to be equal to 1.5 and 1.4 eV, respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114069

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Schottky contacts of TiNxthin films onn‐type Si(100) were fabricated by reactive magnetron sputtering at room temperature.Insituspectroscopic ellipsometry was used to determine the stoichiometry of the TiNxfilms. Dark forward bias current–voltage as well as dark reverse bias capacitance–voltage techniques was used to characterize the diodes in the temperature range from 77 to 300 K. The electrical characteristics of the contacts (i.e., barrier height, ideality factor, and leakage current) as well as the inhomogeneity of the spatial distribution of the barrier heights at the interface are improved drastically for overstoichiometric TiNxfilms obtained by using low negative bias voltage and/or high N2flow rates during the TiNxdeposition. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114070

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The magnetotransport properties in pseudomorphic GaAs/InGaAs/GaAs and AlGaAs/InGaAs/GaAs quantum wells with a Si &dgr;‐doped layer in the barrier close to the quantum well have been investigated. In the GaAs/InGaAs/GaAs system, a giant negative magnetoresistance is observed in the parallel magnetic field configuration. The effect is less pronounced if the doping is performed in the AlGaAs barrier. We attribute this giant negative magnetoresistance to the reduction of an additional impurity scattering process between two‐dimensional states in the quantum well and inhomogeneously distributed donor states in the &dgr;‐doped layer. The experimental results in the GaAs/InGaAs/GaAs system are found to be in excellent agreement with a model that takes into account an oscillation between two‐dimensional states and the &dgr;‐doped layer including an additional momentum in parallel magnetic fields. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114071

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Shubnikov–de Haas (SdH) and van der Pauw Hall effect measurements on In0.52Al0.48As/InxGa1−xAs coupled double quantum wells grown by metalorganic chemical vapor deposition have been carried out to investigate the magnetotransport properties of an electron gas and to determine the subband energies and wave functions in the coupled quantum wells. Transmission electron microscopy measurements showed that In0.8Ga0.2As and In0.53Ga0.47As quantum wells were separated by an In0.25Ga0.75As potential barrier in an active region. The SdH measurements at 1.5 K demonstrated clearly the existence of a quasi‐two‐dimensional electron gas in the quantum wells. The fast Fourier transformation results for the SdH data clearly indicate the occupation of three subbands in the In0.52Al0.48As/InxGa1−xAs coupled quantum wells. Electron subband energies and wave functions in the quantum wells were calculated by a self‐consistent method taking into account exchange‐correlation effects. The first and second excited subband wave functions in the asymmetric quantum well are strongly coupled over both In0.8Ga0.2As and In0.53Ga0.47As wells. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114072

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nb/Al–AlOx–Al/Ta/Nb Josephson junctions for use as energy resolving x‐ray detectors have been fabricated. The junctions have been designed to raise both creation and collection efficiency of quasiparticles. The current–voltage characteristics of the junctions have been investigated on the Al deposition dependence, and found that the characteristics are strongly dependent on the Al deposition rate during the fabrication. The subgap leakage current of those junctions fabricated at higher Al deposition rates exhibit very low leakage current (less than 200 nA at a bias voltage of 100 &mgr;V measured at 0.5 K). ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114073

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We characterized the surface morphology of (110) thin films of 214‐type superconductors epitaxially grown on substrates of 214‐type materials with various degrees of lattice mismatch. By reactive co‐evaporation, (110) thin films of La1.85Sr0.15CuO4and Pr1.85Ce0.15CuO4are grown on (110) substrates of La2CuO4and Pr2CuO4. Reflection high energy electron diffraction, scanning electron microscopy, and atomic force microscopy show the roughness of the film surface is reduced by decreasing mismatch. The surface roughness of La1.85Sr0.15CuO4(110) thin films on La2CuO4substrates is comparably small to that of (001) films on SrTiO3(001) substrates. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114074

出版商:AIP    

年代:1995

数据来源: AIP