摘要:

We report on single electron transport through an asymmetric double dot structure with well-defined dot potential profiles. As the two dots are coupled, the conductance exhibits two pronounced types of Coulomb blockade oscillations. An analysis of the small short-period oscillations indicates the presence of interdot interaction. When the coupling strength is reduced, the oscillations become few irregular peaks but they develop into periodic oscillations again as the drain voltage is increased to 0.6 mV. This appearance with increasing drain voltage is well explained by our model which is based on the stochastic Coulomb blockade model and nonresonant tunneling. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120100

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Transient luminescence spectra are investigated in highly photoexcited CdS nanocrystals (average radii 5.4–100 nm) embedded in glass. Luminescence-intensity kinetics exhibits distortion attributed to carrier-temperature-activated nonradiative recombination due to multiphonon emission. The distortion enhances with reduced crystallite size indicating that the photomodified semiconductor-glass interface originates deep traps with localization barrier of 130 meV. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120101

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electroluminescent devices have been fabricated based onGe+-implantedSiO2films thermally grown on crystalline silicon. Both room-temperature electroluminescence and photoluminescence spectra are found to have three luminescent bands peaked at 3.1, 2.1, and 1.6 eV. The electroluminescent devices have onsets for emission under forward bias of 5 V and under reverse bias of−13 V.Its emission is stable and reproducible. Spectral analyses suggest that the electroluminescent excitation of the 3.1 eV band may be related to the impact ionization by hot electrons, whereas that of the 2.1 and 1.6 eV bands to the radiative recombination of hole-electron pairs. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120102

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The authors demonstratep-i-ntraveling wave photodetectors utilizing low-temperature-grown GaAs as the absorption layer. The electro-optically measured impulse response was found to exhibit a pulsewidth of 1.1 ps full width at half maximum, corresponding to a−3 dBbandwidth of 370 GHz with an external quantum efficiency of 8&percent; at 800 nm. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120115

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Clear exciton absorption peak has been observed at room temperature by photovoltaic spectra, on a GaN layer grown on (0001)-plane sapphire by metalorganic chemical vapor deposition. From the spectra, we obtained the wurtzite GaN room temperatureAandBexciton transition energies, and the energy gap to be 3.401, 3.408, and 3.426 eV, respectively. We have also performed photovoltaic measurements with varied light incidence angles, and observed the polarization behavior of exciton absorption in GaN. In conjunction with previous room temperature photoreflectance measurements, this work provided direct and reliable assessment of GaN semiconductor crystal layers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120103

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The magnetic field dependence of the chemical potential of an electron system can be measured using a metallic single-electron transistor (SET). To demonstrate the method, a SET made of aluminum was fabricated on top of a GaAs/AlGaAs heterostructure containing a two-dimensional electron system (2DES). A change in the chemical potential of the 2DES causes a change in the contact voltage between the SET leads and the 2DES below the SET island which affects the current flow through the SET island. Tuning a voltage which is externally applied in series to the contact voltage, the change in the intrinsic contact voltage can be compensated to keep the SET current constant. With this tuning voltage, the change of the chemical potential by the magnetic field is directly measured. The method described here is applicable to other materials and other parameters affecting the intrinsic contact voltages. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120104

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of lateral dimensions on the relaxation and surface topography of linearly gradedSi1−xGexbuffer layers has been investigated. A dramatic change in the relaxation mechanism has been observed for depositions on Si mesa pillars of lateral dimensions 10 &mgr;m and below. Misfit dislocations are able to extend unhindered and terminate at the edges of the growth zone, yielding a surface free of cross-hatch. For lateral dimensions in excess of 10 &mgr;m orthogonal misfit interactions occur and relaxation is dominated by the modified Frank–Read (MFR) mechanism. The stress fields associated with the MFR dislocation pile-ups result in a pronounced cross-hatch topography. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120105

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Lattice deformation induced in surface GaAs layers by the selective lateral oxidation of buriedAlxGa1−xAslayers was determined from the energy shift of the GaAs phonon line in Raman spectra excited with a focused laser beam. The procedure included a correction for the laser beam induced heating effects. The surface GaAs layer was found under small tensile stress in the oxidized regions of our samples with respect to the unoxidized regions. The deformation is8×10−4and is the same, within experimental error, for heterostructures incorporating pure AlAs layers orAl0.98Ga0.02As.Strong differences in Raman efficiency, as well as in photoluminescence efficiency, were observed for different samples, which are discussed in terms of the GaAs/oxide interface nonradiative recombination efficiency. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120420

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A dual temperature method has been developed for subtracting the 77 K thermally smoothed background from 4.2 K inelastic electron tunneling spectra of ultrathin dielectric metal-insulator-semiconductor junctions. A mode resolving method applied to the remaining spectrum clearly identifies electrode and insulator vibrational modes. The ability to track these relative mode positions and amplitudes shows promise as a unique interface analysis and process diagnostic method. Results are reported on polycrystalline silicon gate, 1.5-nm-thick oxide devices fabricated on 1–10 &OHgr; cm,N-type, (100) silicon substrates by a standard industrial process sequence. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120106

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have created YBCO thin film ramp edge Josephson junctions by modification of the edge surface prior to counterelectrode deposition. No deposited interlayer or barrier layer is employed. These devices are uniform and reproducible, and they display resistively shunted junction current-voltage characteristics with excellent magnetic field modulation.IcRnvalues over the range 0.5–3 mV and correspondingRnAvalues of6×10−8–1.2×10−9 &OHgr; cm2at 20 K are easily attained by varying the process. We believe these junctions offer significant promise as the building blocks of a highTcelectronics technology. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120107

出版商:AIP    

年代:1997

数据来源: AIP