摘要:

We report differential conductance measurements through a double quantum dot with adjustable interdot tunneling rate. The Coulomb gap of the double dot decreases continuously as the interdot tunnel conductanceGintis increased, from the gap of two isolated dots (whenGint∼0)to the gap of a single large dot of twice the total capacitance (whenGint=2e2/h).Excited electronic states in differential conductance measurements on single dots show a spectrum which is essentially independent of the number of electrons in the dot, but is not uniform. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119656

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The generalized photon-carrier rate-equation formalism is used to evaluate the carrier capture process in pseudomorphically strained wurtzite GaN quantum-well lasers. Our results show that both the carrier capture time and the carrier escape time vary significantly with the injected carrier density and strain-induced piezoelectric field. Thus, it is demonstrated that in place of the flatband conditions adopted in most treatments, a self-consistent adjustment of the carrier capture process is essential for achieving an accurate description of carrier dynamics in wurtzite GaN quantum-well lasers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119657

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Infrared laser annealing at a variety of wavelengths (10.0–13.0 &mgr;m) was performed under room temperature for cubic silicon carbide(3C-SiC) films after N-ion implantation by using a free electron laser with features of wide-range tunability, ultrashort pulse operation(∼10 ps),and intense peak power(∼MW).Infrared absorption spectroscopy indicated that the annealing at 12.6 &mgr;m, which corresponds to the absorption peak of Si–C stretch mode, was effective for removing the crystalline damage induced by the ion implantation. On the other hand, Hall effect measurements showed an increase of carrier density for samples annealed at around 10.4 &mgr;m, whereas the absorption was weak at this wavelength. This important result is most likely attributed to the activation of N donors caused by the direct excitation of a local vibration mode associated with N atoms in the SiC matrix. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119668

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Room temperature conductance transients in theSiNx:H/Siinterface are reported. Silicon nitride thin films were directly deposited on silicon by the low temperature electron-cyclotron-resonance plasma method. The shape of the conductance transients varies with the frequency at which they are obtained. This behavior is explained in terms of a disorder-induced gap-state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119658

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Residual strains have been evaluated in a variety of GaN layers grown on sapphire or 6H-SiC from wafer curvature at 293 K, which avoids needing to know the unstrained lattice parameters or energy gap of GaN in advance. Estimated strains at 1.7 K are correlated with the energy of theAfree exciton to determine its strain dependence. We find that strain-free GaN has anAexciton energy of3.468±0.002 eVat 1.7 K, and 293 K lattice parametersa=3.1912 Åandc=5.1836 Å.These values imply that GaN on SiC is frequently under net biaxial compressive stress due to residual lattice mismatch stress, and that several hundred &mgr;m thick GaN layers on sapphire and homoepitaxial layers grown on bulk platelets grown at high pressure are both under about1×10−3in-plane compressive strain. These conclusions conflict with most previous assumptions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119659

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The energy dependence of the cumulative fraction of the damage produced by protons in shielded GaAs solar cells in space is presented. The results show that typically<20&percent;of the damage is produced by protons emerging into the cell with energies<0.1 MeV,including those protons that stop in the active regions of the cell. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119660

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Na-incorporatedCu(In1−xGax)3Se5(Cu(In1−xGax)3Se5:Na)films were prepared by the deposition ofCu(In1−xGax)3Se5layers onNa2S-coated substrates. Electrical properties of theCu(In1−xGax)3Se5:Nafilms were evaluated byI–Vand spectral response measurements of devices with anITO/ZnO/CdS/Cu(In1−xGax)3Se5:Na/Mo/glassstructure. TheCu(In1−xGax)3Se5:Nafilms withx>0showedp-type conduction, whereas forCu(In1−xGax)3Se5without the addition ofNa2S,films withx<0.3showedn-type conduction. The addition of Na was found to have a strong influence on the electrical properties ofCu(In1−xGax)3Se5films as well asCu(In1−xGax)Se2films. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119661

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The dependence of the absorption spectral linewidth of quantum well intersubband transitions on the electron population in the well is experimentally demonstrated. We show that the dependence of the spectral linewidth on the population is substantial and accounts for some of the broadening previously attributed to donor scattering. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119662

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have performed ion channeling characterizations on the (001) and (100) surfaces ofYBa2Cu3O7−xsingle crystals, using 950 keVHe+ions at temperatures ranging from 20 to 780 °C. In oxygen pressures below5×10−5 Torr,we directly observed the surface changes as the sample temperature was increased, and found that the compositional and structural changes occurred from around 400 °C. At higher oxygen pressures, we heated the crystals and performed channeling analysis before and after the heating. We found that theYBa2Cu3O7−xcrystal surfaces were stable at temperatures up to 780 °C in the oxygen pressure range of 1 mTorr–1 Torr. Beyond this range, the surfaces deteriorated at high temperatures. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119663

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The ferromagnetic compoundLa3−3xCa1+3xMn3O10with a triple perovskite structure can be successfully synthesized by using a thin-film growth method. Sputtereda-axis thin films withx=0.3have been examined with respect to their magnetotransport properties. For the triple perovskite compound, we have observed the features, including the enhanced magnetoresistene (MR) effect and the characteristic low-temperature MR effect resulting from intragrain spin-polarized tunneling, which were reported for the double perovskite manganites. A comparison of the magnitude of these features in triple and double perovskite manganites suggests that the features are actually determined by thec-axis Mn–O bond configuration in a layered-perovskite ferromagnet. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119664

出版商:AIP    

年代:1997

数据来源: AIP