摘要:

We present a theoretical study of locally interconnected tunneling arrays operating in the Coulomb blockade regime. In these arrays bits of information are represented by single electrons and useful behaviors can be obtained if the size of a ‘‘dressed’’ electron on the array, i.e., an excess electron plus its polarization cloud, is small. Under this condition, we demonstrate (using simple quasistatic tunneling theory) that linear tunneling arrays can be made to act as charge‐coupled devices for single electrons. Such devices could potentially be applied to computational and/or signal processing applications. As a simplest example, we show that these linear arrays can be made to simulate a random walk. These initial results illuminate some of the requirements on locally interconnected quantum device arrays if they are to do useful computation. More speculatively, they suggest that Coulomb blockade‐based arrays could be the basis for future very high‐powered digital processors. For such hardware to be practical, however, ways of dealing with device nonuniformities (particularly associated with ‘‘polarization charge’’) must be found. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359599

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The temperature dependence of the spectrally resolved cathodoluminescence intensity from a 3.5‐ nm‐thick GaAs‐AlGaAs single quantum well prepared by growth interrupted molecular beam epitaxy has been investigated between 5 and 120 K. As the temperature increases, we observe thermally activated carrier transfer from wider quantum well regions to narrower ones. This observation indicates that there is exciton localization within the wider quantum well regions, one or two monolayers larger in width, at low temperatures. The contrast in spectrally resolved cathodoluminescence images of the quantum well is significantly influenced by this exciton localization and therefore does not necessarily reflect the lateral island distribution. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359336

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An electron beam pumped molecular F*2laser with optical pulse widths up to 160 ns, and an output energy of 1.7 J (optical flux of 4.6 MW/cm2) has been realized. The widths of the laser pulses seem only limited by the duration of the excitation pulse (160 ns). For specific output powers up to 100 kW/cm3no signs of self‐terminating laser pulses due to bottlenecking in the lower laser level have been observed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359337

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electrical and optical properties of undoped InP layers grown at low temperatures by solid source atomic layer molecular beam epitaxy are investigated. Phosphorus surface coverage during epitaxy is controlled by monitoring the evolution of reflection high‐energy electron diffraction pattern during growth. An accurate phosphorus supply by means of a valved cracking phosphorus cell is employed. The relation between phosphorus incorporation and the electronic properties of the epilayers is examined, and it is found that, at a substrate temperature of 340 °C, residual electron concentration increases linearly with phosphorus flux. Residual doping of InP layers grown at 340 °C has been reduced down to 1×1016cm−3, and Hall mobilities of 3260 cm2/V s at 300 K and 14 830 cm2/V s at 65 K are reported. Low‐temperature photoluminescence of low background doping layers is dominated by near band transitions. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359338

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Variation of two‐dimensional electron gas mobility with carrier concentrationnshas been examined for different modulation‐doped heterostructures of AlGaAs/InGaAs/GaAs. It is demonstrated that, depending on the method, electrons are distributed among remote impurity sites and different values of mobility can be achieved for the samensand in the same heterostructure. The origin of this finding is associated with the spatial correlations of remote impurity charges which form dipolelike objects consisting positively charged Si donors and negatively chargedDX−states of the same donor. The effect of correlations causes enhancement of mobility of the order of tens of percent and can explain the appearance of the maximum on a mobility versusnsdependence. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359339

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nuclear magnetic resonance (NMR) of1H was employed to study the population of different sites in proton exchanged LiNbO3using a variety of exchange conditions and proton donors. At least two different proton sites of vastly different mobilities were always found to be present. The ratio of their populations was measured in annealed and as‐prepared samples and found to be strongly dependent upon the exchange conditions. A correlation between our NMR data and recent results obtained using other techniques is discussed in connection with various mechanisms that have been proposed for the changes in the refractive indexes. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359340

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The intrinsic carrier concentration and the Fermi level are calculated using an approximation of the three‐bandk⋅pmodel. The approach is suitable for temperatures from 0 to 400 K and includes the contribution of electrons in the lowest conduction band, heavy holes, and light holes. An approximation for the nonparabolic Fermi–Dirac integral is used in the calculation of carrier concentrations. The resulting expressions are simple and depend explicitly on temperature, semiconductor band gap, carrier effective masses, and nonparabolicity factors. Consequently, the present approach seems suitable for the calculation of intrinsic properties of any semiconductor material for which the three‐bandk⋅pmodel is applicable. The model is compared with a numerical integration of thek⋅pmodel for Hg1−xCdxTe (0.17<x<1) and with experimental measurements (0.2<x<0.29). We also present a comparison between the model and a numerical evaluation of the three‐band model for InGaAs. Because of their simplicity the new expressions seem suitable for both numerical and analytical modeling of semiconductor devices and materials. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359341

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We study the formation and propagation of a normal zone in Rutherford‐type superconducting cables. We use a rectangular conductor model to account for the electric current redistribution process between the multifilamentary strands in the presence of a normal zone. We obtain and integrate numerically the diffusion equations for the temperature and the current density distributions. Our simulations show the formation of stable normal domains propagating along the cable for certain values of the current and parameters characterizing the cable and cooling conditions. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359342

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigated the effects of fluorine on boron diffusion in thin silicon oxides used for metal‐oxide‐semiconductor structures, including silicon dioxide and oxynitride. We used secondary ion mass spectroscopy to measure the boron penetration depth fromp+‐polycrystalline silicon to the silicon substrate through the silicon oxides for various fluorine doses. We compared experimental and simulated results and determined the boron diffusion coefficients in the silicon oxides. The diffusion coefficients have an Arrhenius relationship for each fluorine dose. The diffusion coefficients at a fluorine dose of 1×1016cm−2were 30 times larger than with no fluorine dose, and at a fluorine dose of 1×1015cm−2, diffusion coefficients were 5 times larger. With oxynitride, fluorine has the same enhancing effect. With no fluorine, the diffusion coefficients were independent of oxide thickness. When fluorine is implanted into polycrystalline silicon, especially with a high dose, the diffusion coefficient is larger for thinner oxides because of the higher fluorine concentration. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359343

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In order to investigate the behavior of AlxGa1−xAs lattice relaxation caused by opposite directions of biaxial stress, i.e., tensile or compressive stress, AlxGa1−xAs (X=0–0.45) layers were grown on undoped and heavily In‐doped GaAs substrates by organometallic vapor phase epitaxy. Al0.45Ga0.55As layers on undoped GaAs substrates are subject to biaxial compressive stress and have a large coherent length. Al0.3Ga0.7As layers grown on heavily In‐doped GaAs substrates with a lattice constant larger by about 0.1% than that of undoped GaAs are subject to biaxial tensile stress and have much smaller coherent length. Furthermore, it is found that the coherent length depends on the growth temperature and that an increase in coherent length is brought in by the introduction of even a small amount of Al in the layers. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359345

出版商:AIP    

年代:1995

数据来源: AIP