摘要:

A silicon single electron tunneling transistor (SETT), which shows an inverting voltage gain greater than unity and as high as 3.7, has been fabricated. The blockade voltage as a function of gate voltage shows sawtooth oscillations when biased with a small current and measured at a temperature of 4.2 K. The SETT is fabricated in highly doped and oxidized silicon quantum wires of less than a40 nm×50 nmcross section and 1.5 &mgr;m length. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120543

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Aluminum gallium nitride(AlxGa1−xN)films withx=0tox=0.36,grown by metal–organic chemical vapor deposition on sapphire, were characterized by cathodoluminescence (CL) imaging and spectroscopy, photoluminescence (PL) spectroscopy, and optical microscopy. In each film, the CL and PL spectra excited from the top surface show a narrow band-edge peak and a broad deep-level peak. In some films, the PL spectrum excited from the film–substrate interface (through the sapphire substrate) shows an additional narrow peak below the band edge, which is attributed to interfacial defects. CL imaging and optical microscopy reveal two types of large-scale defects: networks of lines, which are probably microcracks, and roughly hexagonal raised areas. The hexagonal areas occur only in the lower-xfilms, while the microcrack density increases withx. Spatially resolved CL spectra taken near the large-scale defects show large peak shifts attributed to stress relaxation, and below band-edge peaks attributed to localized states. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120520

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The defects generated inSiO2during irradiation with energetic (10 eV) photons were found to trap electrons at a level 3.1 eV below the oxide conduction band. The electron spin resonance data and the behavior upon hydrogen passivation indicate that the optically active state may be ascribed to a H-complexed oxygen vacancy inSiO2.The observed injection of electrons to these traps from Si advances the revealed defects as the possible origin of the degradation-induced electrical conduction of thinSiO2layers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120521

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

ZnS1−xTex-based Schottky photodiodes have been fabricated on various substrates using the molecular beam epitaxy technique. The photovoltage output of these photovoltaic devices is determined using Fourier transform interferometric spectroscopy. The results show that these devices (withTe<10&percent;) are highly sensitive in the ultraviolet but are visible blind. An external quantum efficiency of over 50&percent; has been achieved on a device grown on a GaP substrate and over 40&percent; on a Si substrate. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120522

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

It has been shown that a two-peak green photoluminescence (PL) of porous silicon (PS) can be obtained from a continuous blueshift of a red PL by positron irradiation. At room temperature, PS samples were irradiated in air by energetic positrons coming from the conventionally used isotope22Na(∼20 &mgr;Ci).With increasing positron irradiation time, an originally red PL shifted continuously to green, then a two-peak PL appeared with a weak high-energy emission band (529 nm) and a low-energy dominant band (562 nm). The intensity of this high-energy band was enhanced by prolonged positron irradiation. The electron-spin-resonance signal combined with infrared absorption showed that positron irradiation created dangling bonds and stimulated oxide growth in PS. An interpretation is given on the basis of quantum confinement and atomiclike nature for very small nano-Si crystallites. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120523

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Organic thin film transistors (TFTs) have been fabricated using thermally evaporated films of the oligophenylsp-quaterphenyl (p-4P),p-quinquephenyl (p-5P), andp-sexiphenyl (p-6P). The field-effect mobility of these TFTs ranges from10−2 cm2/V sforp-4P to10−1 cm2/V sforp-6P with on/off current ratio from105to106.These values are comparable to those achieved using the more widely studied organic semiconductors alpha-sexithienyl (&agr;-6T) and pentacene. X-ray diffraction reveals a high degree of molecular ordering, believed to be important for obtaining high field-effect mobility in organic TFTs. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120524

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We show how optical phonons can be used as efficient probes in self-organizedSi1−xGexislands grown on Si(001). Both the alloy composition and residual strain in the islands were originally determined from the phonon frequencies and Raman intensities. The experimental results are in good agreement with the strain relaxation simulated by means of the finite element method. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120525

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Using high resolution transmission electron microscopy, a thin pseudomorphic AlN layer (2–3 nm) has been observed at the metal/GaN interfaces of Ti/Al(35/115 nm)and Pd/Al(25/125 nm)ohmic contacts ton-type GaN annealed in Ar at 600 °C for 15 and 30 s, respectively. The interfacial layer has ac-plane (002) lattice spacing of2.48±.03 Åand ana-plane (100) spacing matching that of GaN (2.76 Å), and the identification of this layer as AlN is consistent with chemical analysis by energy dispersive x-ray spectroscopy. The formation of this interfacial AlN layer coincides with the onset of ohmic behavior in Ti/Al and Pd/Al contacts annealed at 600 °C and may be the cause. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120526

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The relative contributions of interstitials and vacancies to diffusion of a dopantAin silicon are specified by the interstitial fraction of diffusivity,fA.Accurate knowledge offAis required for predictive simulations of Si processing during which the point defect population is perturbed, such as transient enhanced diffusion. While experimental determination offAis traditionally based on an underdetermined system of equations, we show here that it is actually possible to derive expressions that give meaningful bounds onfAwithout any further assumptions but that of local equilibrium. By employing a pair of dopants under the same point-defect perturbance, and by utilizing perturbances very far from equilibrium, we obtain experimentallyfSb⩽0.012andfB⩾0.98at temperatures of∼800 °C,which are the strictest bounds reported to date. Our results are in agreement with a theoretical expectation that a substitutional dopant in Si should either be a pure vacancy, or a pure interstitial(cy)diffuser. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120527

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The light beam induced current (LBIC) technique was used to characterize the interface formed by the wet oxidation of AlAs andAlxGa1−xAs(x=0.98and 0.95). LBIC scans were used to calculate the diffusion lengths of minority carriers both in the bulk and near these interfaces; and the corresponding interface recombination velocities were estimated. The interface recombination velocity at the oxide/semiconductor interface is3.13×105 cm/sfor AlAs, and1.90×104 cm/sforAl0.98Ga0.02As.It is found that the addition of gallium in the AlAs can significantly improve this property. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120545

出版商:AIP    

年代:1997

数据来源: AIP