摘要:

We report on quantum transport in the presence of an electron reflection grating fabricated within a high electron mobility transistor structure. The grating was composed of a periodically corrugated potential wall by which the electron waves are diffracted. The low temperature conductance shows a number of peaks with respect to the gate voltage, which are consistent with the electron diffraction effect and are predicted by the Fraunhofer diffraction condition. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120389

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We propose a novel photodetector capable of multi-spectral channel operation. The device makes use of the ability of a quantum dot plane to capture an optical spectrum, and of a resonant-tunneling structure to perform spectrally sensitive read-out. We present a design made out in theInAs–GaAs–AlxGa1−xAssystem. We also present realistic simulations of the optical channel capabilities, as well as a discussion of the possible problems of the device. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120390

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a smart pixel with surface-normal optical input and output beams using a vertical cavity surface-emitting laser. In its present nonoptimized hybrid version, the smart pixel exhibits opto-optical switching with a contrast of 35 dB, an optical gain of 55 dB and a 3 dB bandwidth of 90 MHz. The optical switching energy is 715 fJ. NOR, and NAND logic operations at 4 Mbit/s with a fan-out of 5 are also demonstrated. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120391

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Germanium quantum dots have been grown on Si substrates at various temperatures for different durations and studied with atomic force microscopy to determine the growth conditions for the smallest and most uniform size quantum dots.Ge1−xCxquantum dots grown at varying Ge:C ratios have been characterized to study the effects of strain compensation by C. The effects of P and B doping on both Ge andGe1−xCxdots have also been investigated. The results show fewer quantum dots inGe1−xCxdue to strain compensation of Ge by C, and suggest the formation of larger dots with P doping and smaller and more uniform dots with B doping. X-ray diffraction measurements on the samples show the strain in the films, with the rocking curves changing with the ratio of C in the quantum dots. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120392

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Relaxed SiGe thin films are used as templates to control the nucleation of three-dimensional Ge islands on Si(100) substrates. Using the relaxed template, Ge islands form a rectangular array with all islands located exclusively above the intersections of dislocations. The registration is lost when the Ge growth temperature is lowered to 300 °C, and the Ge coverage is decreased to 0.4 nm. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120393

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have demonstrated that GaN can be grown epitaxially by atmospheric pressure metalorganic chemical vapor deposition on an aluminum oxide compound layer utilized as an intermediate layer between GaN and a Si(111). X-ray diffraction measurement indicates that single-crystal hexagonal GaN with its basal plane parallel to the Si(111) plane is grown. Using a scanning electron microscope, the macroscopic evolution of GaN grown on theAlOx/Si(111)substrate is found to be similar to that of GaN grown on a sapphire(0001) substrate. Cathodoluminescence (CL) spectrum shows a unique emission that consists of several peaks with the intensity comparable to that of the near-band-edge emission. Unique characteristics in CL spectrum are discussed in terms of a possible oxygen contamination of GaN grown on theAlOx/Si(111)substrate. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120394

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

WhenNdBa2Cu3O7−&dgr;(Nd123) is melt-textured in low oxygen partial pressure(Po2)and subsequently annealed in oxygen to produce the superconducting phase, there is a considerable enhancement of flux pinning compared to Y123. This enhancement is accompanied by a precipitation mechanism due to a change of the solubility limits ofNd1+xBa2−xCu3O7−&dgr;between the high temperature lowPo2conditions used in melt-textured growth and the low temperature oxygen annealing. Transmission electron microscopy reveals a coherent intermediate precipitate structure with a composition ofBaCuO2and a high density of dislocations. We believe these defects are responsible for the strong flux pinning in this material. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120395

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

SuperconductingNb–In0.53Ga0.47As/In0.77Ga0.23As/InP–Nbcontacts with an electrode separation of 450 nm were fabricated. Due to the high mobility of the two-dimensional electron gas, the current transport can be described within the clean limit regime. At 0.3 K a critical current of 3.8 &mgr;A was obtained for 6 &mgr;m wide contacts leading to a characteristic voltage of 190 &mgr;V. The decrease of the critical current with increasing temperature can be explained by a theory developed by A. Chrestin, T. Matsuyama, and U. Merkt [Phys. Rev. B49, 498 (1994)], which takes &dgr;-shaped barriers at the superconductor/semiconductor interfaces into account. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120410

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report low voltage (1.5–3 V) performance of ferroelectricPb(Zr,Ti)O3based capacitors. La substitution up to 10&percent; was performed to systematically lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a(Ti0.9Al0.1)N/Ptconducting barrier composite. Ferroelectric capacitors substituted with 10&percent; La show significantly lower coercive voltage compared to capacitors with 0&percent; and 3&percent; La. This is attributed to a systematic decrease in the tetragonality (i.e.,c/aratio) of the ferroelectric phase. Furthermore, the samples doped with 10&percent; La showed dramatically better retention and pulse width dependent polarization compared to the capacitors with 0&percent; and 3&percent; La. These capacitors show promise as storage elements in low power high density memory architectures. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120396

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Scanning near-field optical microscopy using a slit-type probe is discussed. The slit-type probe has a width of much less than a wavelength, &lgr;, and a length on the order of &lgr;, and thus has high transmission efficiency. Two dimensional near-field images of objects have been constructed using an image reconstruction algorithm based on computerized tomographic imaging. Experiments performed at 60 GHz(&lgr;=5 mm)show that this type of near-field microscopy can achieve a spatial resolution of better than&lgr;/45for two dimensional imaging. A method for fabricating a submicron width slit probe at the end of an optical fiber is presented for extending this microscopy to optical waves. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120397

出版商:AIP    

年代:1997

数据来源: AIP