摘要:

We formulate and discuss principles for designing computationally useful networks of Coulomb‐blockade devices. Our particular focus is on locally interconnected synchronous networks in which the numerical discreteness of a computation is represented directly by the quantization of electron charge, i.e., electrons represent bits. To highlight our emphasis on circuits and architectural issues, and on performing locally interconnected computation rather than traditional logic as has been the interest heretofore (single‐electron logic), we refer to our networks as single‐electron digital circuits (SEDCs). In addition to being single‐electron and locally interconnected, the SEDCs we propose have a regular ‘‘cellular’’ structure with occupancy‐independent biasings and with electron‐electron interactions carefully controlled. The chief virtue of SEDCs is their scalability, both as devices (because of their Coulomb blockade basis) and as circuits (because of their local interconnectivity), perhaps even to molecular dimensions. We illustrate our approach with a number of new ‘‘device’’ and network designs based on electron‐pump‐like structures and mostly directed at performing lattice‐gas simulation. For this application we effectively create an electron gas within a SEDC which precisely mimics the lattice gas. Finally, we have validated our designs using numerical simulation and expect that at least some of them should be realizable in current technology. However, their promise of enormous levels of integration and performance should be tempered with a clear awareness of the many obstacles associated with fabrication and economics which must be overcome if they are ever to be the foundation for a practical computer technology.

ISSN:0021-8979    

DOI:10.1063/1.360861

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The molecular‐beam‐epitaxial growth of InxGa1−xAs on GaAs or AlyGa1−yAs leads to a variation of In content with depth, due to In segregation. However, by predepositing In at the beginning of InxGa1−xAs growth, and also thermally removing the excess In at the end, we can produce a layer with the ideal ‘‘square’’ In profile. We find that the performance of AlyGa1−yAs/InxGa1−xAs/GaAs high electron mobility transistors is most enhanced by the predeposition step alone. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360862

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The electrical characteristics of buried‐gate,n‐channel junction‐field‐effect transistors (JFETs) fabricated in epitaxial layers grown on 6H–SiC wafers have been measured as a function of temperature, from 218 to 773 K (−55 to 500 °C). The data are in good agreement with predictions of a model that uses standard abrupt‐junction, long‐channel JFET device equations for which the carrier concentration is calculated based on a two‐level ionization structure for the nitrogen donor. An inverse power‐law dependence of carrier mobility on temperature is assumed based on recent measurements of Hall mobility in epitaxial films of comparable doping. The only free parameter of the model is the compensation density, which is chosen by fitting the calculated saturated drain current to the measured value at room temperature. There are some deviations between the calculated and measuredI–Vcharacteristics at both temperature extremes (218 and 773 K), which are attributed to increased substrate resistivity at 218 K and to increased gate leakage current at 773 K.

ISSN:0021-8979    

DOI:10.1063/1.360863

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The texturing process of Bi–Sr–Ca(Dy)–Cu–O (2212) is optimized by sintering under a magnetic field. The precursor crystalline powder is melted and grown under a 1.2 T magnetic field. Textured samples are characterized by x‐ray diffraction, scanning electron microscopy, electrical resistivity, and magnetic susceptibility. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360864

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Electron paramagnetic resonance (EPR) has been used to detect Ni+impurities substituting for Ag+ions in a single crystal of AgGaSe2. The observed EPR spectrum has axial symmetry about thecaxis of the crystal and is described byg∥=2.635 andg⊥=2.241. A partially resolved hyperfine pattern in thec‐axis spectrum is consistent with equivalent interactions with fourI=3/2 nuclei (e.g.,69,71Ga). The concentration of Ni+ions in the undoped crystal was approximately 7×1017cm−3. These substitutional Ni+impurity ions are suggested to be responsible for the polarized 2.2 &mgr;m absorption band that is presently limiting the use of AgGaSe2as a 2 &mgr;m pumped optical parametric oscillator with mid‐infrared output. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360865

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Thermally induced reactions at SiO2/Al interfaces are investigated by cross‐sectional transmission electron microscopy. For the SiO2/Al interfaces fabricated by chemical vapor deposition of SiO2on polycrystalline Al films, precipitates of reduced Si as the reaction products are observed in the Al films and along the SiO2/Al interfaces, after annealing at 500 °C for more than 2 h. On the other hand, the interfaces fabricated on the single‐Al(111) films show no precipitation even after 4 h of annealing. The differences in the interfacial reactivities are discussed in relation to the existence of grain boundaries and Al film orientations. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360866

出版商:AIP    

年代:1996

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.362719

出版商:AIP    

年代:1996

数据来源: AIP