摘要:

AmorphousSiO2was deposited on three single-crystalline substrates: alumina,CaF2,and hydrogen-terminated silicon, by chemical vapor deposition (CVD) using tetraethoxysilane (TEOS) and ozone(O3).The deposited layers were then examined by using atomic force microscopy (AFM). For deposition times of 3, 8, 15, and 180 s, the film thickness ranged from less than 2.4 to 150 nm, respectively. Comparison of the surface roughness with the film thickness, as determined independently by ellipsometry, indicated that the thinnest film formed on the silicon surface (2.4 nm) was continuous. During film formation, for all three substrates, the surface roughness increased initially, reached a maximum, and then decreased. Surprisingly, the surface became smooth (within the resolution of 0.2 nm of our AFM). For the silicon substrate, this smoothing occurred between 3 and 8 s, which corresponds to 2.4 and 6.4 nm of deposition, respectively. Furthermore, just before the smoothing started, the surface of the deposited film contained protuberances, 1.6 nm high and 16 nm×16 nm in area. This indicates that smooth film of a few tens angstroms in thickness can form on the silicon. The smoothing of the protuberances occurred between 3 and 8 s for theCaF2substrate, and between 15 to 180 s for the alumina substrate. The initial formation of a rough surface followed by smoothing is likely to be inherent inTEOS/O3CVD systems, irrespective of substrate type. Surface-tension-induced flows of the surface, which has liquidlike properties, is a plausible mechanism. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366081

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The use of a new highly luminescent conjugated polymer as an emissive layer in single and multilayer electroluminescence devices is reported. Poly(m-phenylenevinylene-co-2,5 -dioctyloxy-p-phenylenevinylene) [PmPV-co-DOctOPV] was prepared via a Wittig synthesis reaction. The resulting polymer has a high photoluminescence quantum efficiency in the solid state with an emission spectrum peaked at 506 nm (2.45 eV) in the green. Electroluminescence devices were fabricated with an ITO anode and a MgAg cathode. Three different structures were studied: (i) single layer devices containing only PmPV-co-DOctOPV; (ii) double layer devices with PmPV-co-DOctOPV and an evaporated film of 1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazoyl) phenylene [OXD-7] as an electron transport layer; (iii) triple layer devices containing PmPV-co-DOctOPV, OXD-7 and in addition a polyvinylcarbazole hole transport layer. Electroluminescence external quantum efficiencies for these devices were found to be up to 0.08&percent;, 0.55&percent;, and 1&percent;, respectively, corresponding to luminous efficiencies of≈0.5,≈3,and≈6 lm/Wand power efficiencies of8.5×10−5,5.9×10−4,and6.0×10−4 W/W.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366097

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Experimental results on low frequency noise in quasiself-aligned bipolarn-p-njunction transistors, with widely varying emitter/base junction dimensions are presented and compared with former results obtained on devices of the same type. The power spectral density of base current fluctuations was found to depend linearly on the inverse of the area of the emitter/base interface junction, implying localization of the low frequency noise sources on the interface, rather than on the transistor perimeter. An application of current-to-voltage converters for studies of current fluctuations is also discussed and compared with a more conventional technique. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366082

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effects of electrical stress on static characteristics and power spectral density,SIb,of base current,Ib,fluctuations at low frequencies,f<1kHz, have been studied in quasiself-aligned bipolarn-p-njunction. In as-fabricated devicesSIb∝1/AE,whereAEis the transistor emitter area, whereas in strongly degraded transistorsSib∝1/PE,wherePEis the transistor perimeter. The latter demonstrates directly that hot carrier-induced noise sources are generated at the periphery of the transistors, in agreement with former work on hot electron-induced aging of bipolar junction transistors. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366083

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

8–12 &mgr;m InGaAs/GaAs quantum well infrared photodetectors with two different well doping concentrations have been studied. The devices with and without surface gratings are compared for normal incident operation. It is found that the TE to TM absorption ratio depends on the doping density in the quantum wells. A higher doping density increases TE absorption. A detectivity about1×1010 cm Hz1/2/Wand a peak responsivity of 0.23 A/W at 9 &mgr;m have been obtained for the grating-free devices. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366084

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This article discusses the electrical characterization of low-temperature intrinsic Si films deposited by remote plasma-enhanced chemical vapor deposition. Metal-oxide-semiconductor (MOS) capacitors were fabricated on films deposited over a range of temperatures. Conventional MOS measurements such as capacitance versus voltage, breakdown voltage, Zerbst plot, and charge-to-breakdown were used to analyze the capacitors. The results of these measurements not only yielded information about the electrical properties of the films, but also led to conclusions regarding structural quality and the presence of metal contamination. This, coupled with the fact that capacitor fabrication requires only a simple, moderate-thermal budget process, makes MOS capacitor measurements an attractive technique for the characterization of low temperature epitaxial Si films. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366085

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A formula in terms of the equivalent circuit parameters of a resonant tunneling diode (RTD) and its loading for three different equivalent circuit models of RTD’s is derived to describe the apparent change, occurring in the presence of unstable oscillation, in the negative differential conductance (NDC) region of dc current-voltage(I-V)characteristics measurements. The measured experimentalI-Vdata and the related parameters of RTD’s from several fabricated devices are applied to the formula in terms of the stability and instability criteria to do the numerical verification. It has shown good agreement between the derived formula and the experimentalI-Vdata of RTD. Simulated program with integrated circuits emphases (SPICE) simulation shows the flattened and the broken sections, which represent the occurrence of the unstable oscillation, appearing in the NDC region ofI-Vcurve, which also validates the applicability of the derived formula. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366086

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The carrier transport equations for a siliconp-i-nphotodiode have been linearized, and analytic solutions of the responsivity have been obtained for a step function of weakly absorbed radiation. These solutions have been used to calculate the responsivity toQ-switched pulses (tens of nanoseconds) from a Nd:YAG laser. Examples of the tradeoff between responsivity and electrical pulsewidth are given. Finally, the use ofp-i-nphotodiodes to detect mode locked (tens of picoseconds) pulses by taking advantage of the long period between pulses is shown to be feasible if the pulse shape does not have to be resolved. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366087

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Stochastic resonance (SR) occurs in bistable nonlinear systems subject to noise, as the entrainment of their output by a weak periodic modulation added to the input. Electronic computation involves switching of memory elements between two states that correspond to 1 and 0, respectively. The possibility of switching errors due to SR in memory elements is considered, showing that it represents a negligible danger to reliable computation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366088

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have examined the Raman spectra of violet and infrared emittingGe+-implantedSiO2films with special emphasis upon annealing temperature (AT) dependence of Raman scattering. We found that the complete spectrum mainly consists of three bands at 220–280, 300, and 430cm−1, corresponding to scattering of Ge-related components, Ge nanocrystallites, and localized Si–Si optical phonons in the Ge neighborhoods, respectively. The Ge crystalline band shows an obvious AT dependence. The theoretical result from the phonon confinement model can predict its linewidth change with AT, but cannot explain its constant peak frequency. Based on the experimental result from x-ray diffraction, we attributed the discrepancy mainly to the compressive stress exerted on Ge nanocrystallites, which leads to the upshift of Ge crystallite peak thereby basically compensating the downshift caused by the confinement on phonon frequency. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366089

出版商:AIP    

年代:1997

数据来源: AIP