摘要:

In this letter we report the measurement result of intrinsic carrier capture time in deep-etched quantum-box (70 nm diameter) lasers at low temperature (2 and 77 K). In order to investigate intrinsic carrier capture and relaxation mechanism, we have to rule out the contribution of the geometry factor and derive the local quantum capture time. For this purpose, lasers with the same box size (70 nm) but different box densities, that are arranged as two-dimensional periodic arrays for distributed feedback operations are prepared and measured. We find that the quantum capture time of the box lasers determined at 2 and 77 K is only about 2.4 ps and is smaller than the corresponding value of the quantum-well lasers. This is a direct experimental indication of the existence of an efficient channel for carrier capture and relaxation in the quantum-box system investigated. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118510

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Subband separation energy dependence of intersubband relaxation time in a wide quantum well (250 Å) was studied by steady-state and time-resolved photoluminescence. By applying a perpendicular electrical field, the subband separation energy in the quantum well is continuously tuned from 21 to 40 meV. As a result, it is found that the intersubband relaxation time undergoes a drastic change from several hundred picoseconds to subpicoseconds. It is also found that the intersubband relaxation has already become very fast before the energy separation really reaches one optical phonon energy.©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.118511

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A long-term delayed increase in the 1/fnoise ofp-channel metal–oxide–semiconductor (MOS) transistors is observed in devices that show significant latent interface-trap buildup after exposure to ionizing radiation. During positive-bias postirradiation anneal, the noise increases by more than an order of magnitude above the level observed after irradiation. The increase in noise precedes the latent buildup of interface traps by at least 4.5 days during room-temperature annealing, and by ∼1 h during 100 °C annealing. The time and temperature dependencies of the increases in noise and interface trap buildup are consistent with the thermally activated motion of protons into the near-interfacial region of the oxide, followed by increases in border trap and interface trap densities. These results suggest hydrogen-related species can significantly affect the 1/fnoise of MOS devices.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118512

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A technique for the selective-area growth of GaAs on a nanometer scale is described. The technique comprises nitrogen (N)-passivation mask formation, scanning-tunneling-microscopy (STM) pattern modification, and metalorganic molecular-beam epitaxy. GaAs (001) surfaces are passivated with N radicals dissociated fromN2molecules and are modified by STM on a nanometer scale. GaAs nanostructures are then grown on the modified areas using trimethylgallium and tertiarybutylarsine. Uniform 6-nm-high and50×50-nm2dots were formed on50×50-nm2STM-modified areas. The advantage of the technique is that size-controlled nanostructures can be fabricated in specific positions and these nanostructures are free from contamination because all processes are performed in a vacuum. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118513

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Large depression ofTcat 7° [100] tilt grain boundaries was observed in bulkBi2Sr2CaCu2O8+&dgr;(Bi2212) bicrystals by measuring the zero-field electrical transport properties of the grain boundaries and the constituent single crystals over an extended range of currents and voltages. TheTc-depressed region was determined to be around 20 nm, comparable to the width of the strain field associated with the observed array of grain-boundary dislocations. Superconducting coupling of the grain boundaries increases sharply as temperature decreases below the grain-boundaryTc≅68K. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118514

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ramp-type Josephson junctions with highly dopedPrBa2Cu3−xGaxO7−&dgr;barrier layers (x=0.7, 1.0) have been investigated by high-resolution electron microscopy. A Ga-rich intergrowth and Ga diffusion in the ion-milledSrTiO3substrate are observed. The Ga segregation is responsible for the deviating electrical behavior as expected from extrapolation of low doping levels (x=0.1–0.4). The Ga diffusion in the ion-milled substrate, and possibly in the base electrode, may hamper Josephson junction fabrication using substitutedREBa2Cu3O7−&dgr;materials (RE=rare earth).©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118515

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A superconducting switch has been developed using the magnetic fringe field of a ferromagnetic film to control the critical current in an underlying superconductingSnfilm. The magnetization of the ferromagnet is rotated in the plane of the film to vary the magnitude of the fringe field applied locally to the superconductor from negligible to substantial values. A large suppression of the critical current is observed. Applications as an amplifier and a nonvolatile storage cell are possible, and a device based on highTcmaterials has promise. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118482

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Epitaxial films (1.7 &mgr;m thick) with the compositionPbFe12.9O22.9and hexagonal lattice parametersa=5.12 Å andc=23.67 Å have been pulsed laser deposited at 600 °C in 50 mTorr ofO2onto single-crystal (0001) sapphire substrates. Epitaxy was determined using standard powder x-ray diffraction (XRD) and grazing incidence XRD. The films were deposited using a single-phase polycrystallinePbFe12O19target. The composition of the films isPbFe12.9O22.9,which was measured using Rutherford backscattering spectrometry. Static magnetic measurements were performed using a vibrating sample magnetometer and SQUID magnetometer in order to measure magnetic anisotropy, magnetic remanence(Mr),coercive field(Hc),and saturation magnetization(4&pgr;Ms)of the films. ThePbFe12.9O22.9films exhibit magnetically isotropic behavior in the film plane with remanence ratio(Mr/Ms)andHcvalues of 88±2.9&percent; and 2500±97 Oe, respectively. However, the films are anisotropic with respect to the film normal such that thecaxis is a magnetically hard direction and all directions normal to thecaxis are magnetically easy (i.e., a planar anisotropy field,HA,with an estimated magnitude of 77.5 kOe). The4&pgr;Msvalue for the films is 630 Gauss at room temperature. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118483

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Anisotropic bulkSm2(Fe,M)17Nxmagnets were prepared by rotation aligning easy planeSm2(Fe,M)17powders followed by sintering and nitriding. Vanadium substitution for iron can help thec-axis alignment compared to the binarySm2Fe17compound. Magnets with an energy product of 15 MG Oe and an intrinsic coercivity of 7 kOe were obtained on a single phaseSm2Fe16.15V0.85Nxcompound with a density of 91&percent; of theoretical density. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118478

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a novel surface-controlled bistable nematic liquid crystal display. This black and white device uses simple monostable planar anchorings and a dielectrically positive nematic. The two bistable textures are, respectively, quasiuniformUand almost half-turn twistedT. Short electric pulses break the surface anchorings. Hydrodynamically coupled breaking of both anchorings createsT.Uis obtained by breaking only one anchoring. Write and erase times for high resolution video are achieved at voltages compatible with the usual drivers.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118479

出版商:AIP    

年代:1997

数据来源: AIP