摘要:

We observe a polarization instability in circularly symmetric vertical‐cavity surface‐emitting lasers. A relatively long time, 3–5 ns, is required to establish a dominant polarization state. Under high‐speed digital modulation this leads to strong enhancement, 20–30 dB, in polarization resolved low‐frequency relative intensity noise. This polarization instability is accurately described by a simple rate‐equation model. A similar increase in relative intensity noise, under dc bias, is caused by energy partition between orthogonally polarized modes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114746

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Microgun‐pumped lasers, in which electron beam pumping is achieved via an array of low‐voltage, field‐emission microtips, were demonstrated in the blue and blue‐green regions of the spectrum. The devices exploit graded index, separate confinement Zn1−xCdxSe/ZnSe heterostructures grown by molecular beam epitaxy on In1−xGaxAs(100) substrates. Lasing thresholds were in the 4–20 kW/cm2range for temperatures between 83 and 225 K, and the device lifetime exceed several hours at a 12.5% duty cycle for a laser operating at 83 K and a wavelength of 478.4 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114747

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The frequency dependence of the shear stress of metal‐particle/insulating oil electrorheological (ER) fluids under an ac electric field has been studied. The results show that the shear stress of the metal‐particle ER fluid under a fixed electric field increases with increasing frequency and then tends to a saturated value at higher frequency. The shear stress at 103Hz is much larger than that under a dc field. The transition of the shear stress shifts to higher frequency when the conductivity of the fluid is larger. The measurements are consistent with the theoretical model proposed by Davis [J. Appl. Phys.73, 680 (1993)]. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114748

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The influence of nitrogen on the growth of diamond using the gas mixtures of CH4–CO2by microwave plasma chemical vapor deposition was investigated. A clear improvement in the surface morphology and quality of the diamond films indicates the beneficial effect of adding nitrogen to CH4–COgas mixtures. Analysis using Auger electron spectroscopy and secondary ion mass spectroscopy shows very low and uniform levels of nitrogen in the diamond films. Atomic nitrogen plays a dominant role in C/H/O/N plasma chemical vapor deposition processes because of the amount of oxygen atoms increased via the titration reaction of nitrogen atoms (a high‐rate reaction): N+NO→N2+O. This produces a significant influence on diamond synthesis in a CH4–CO2–N2gas mixture. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114749

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Amorphous, 10‐nm‐thick tantalum‐silicon‐nitride (TaSiN) layers were found to be effective diffusion barriers between copper and thermal silicon dioxide. The films were electrically evaluated using TaSiN/Cu/TaSiN‐oxide‐silicon capacitors and bias thermal stress (BTS) treatments; the capacitors were stressed at 300 °C with electric fields in excess of 1 MV/cm for up to 80 h. High frequency capacitance versus voltage characteristics were recorded at room temperature before and after BTS treatment. Based upon comparisons between these (C–V) curves, barrier failure was concluded to have not occurred. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114750

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have found that NdBa2Cu3Ox(NBCO) thin films, fabricated by the laser ablation process, have highly stable and smooth surfaces. Clear spiral patterns with 4–5 terraces are observed all over the film area with an atomic force microscope (AFM) operating in air. We have also obtained atomically resolved image of the spiral terraces using AFM, and also using ultrahigh vacuum scanning tunneling microscope. This study suggests that NBCO film is a good candidate for device applications. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114751

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effect ofinsituphotoexcitation during boron ion implantation on subsequent transient enhanced B diffusion in Si has been investigated. Photoexcitation using a mercury arc lamp was performed during B+implantation at 35 keV for a dose of 5×1014cm−2at 177 K. A reduction in the electrical activation dip, i.e., reverse annealing effect, in the temperature range 550–700 °C was observed. Also, the transient enhanced diffusion of B, measured using SIMS following 800 °C, 30 min annealing, was suppressed. Both effects demonstrate that the creation of self‐interstitials during the implantation process is significantly reduced. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114752

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Be diffusion during post‐growth annealing has been studied in InGaAs epitaxial layers, grown between two undoped InGaAs layers. To explain the observed concentration profiles and related diffusion mechanisms, a general substitutional–interstitial model is proposed. On the one hand, a simultaneous diffusion by dissociative and kick‐out models is suggested and, on the other hand, the Fermi‐level effect is used to explain the functional dependence change of the effective diffusion coefficient of beryllium species with its concentration. The concentration dependent diffusivity has also been covered to perform an improved data fitting of Be diffusion profiles. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114753

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A thin (1–3 nm) Ti layer is shown to improve the uniformity and the thermal stability of CoSi2layers grown on Si substrates. The beneficial effect of the Ti(TiN) cap is demonstrated for a variety of CoSi2layers, including Ti‐interlayer mediated epitaxial (TIME) CoSi2/Si(100), polycrystalline CoSi2/Si(100), and CoSi2/polycrystalline Si. The increased uniformity and stability of the silicide layers are speculated to result from reduced surface and interface diffusion during nitrogen and/or vacuum anneals. In the case of TIME CoSi2/Si(100), both the use of a Ti cap and the removal of a metastable Ti4Co4Si7overlayer prior to high‐temperature anneals are found important for the fabrication of uniform, single‐crystal layers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114754

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The compensating acceptors and donors in nitrogen &dgr;‐doped ZnSe epilayers grown by molecular beam epitaxy using a nitrogen rf‐plasma source are studied by means of photoluminescence (PL) and photoluminescence excitation spectroscopy (PLE). The temperature dependence of PL and PLE spectra obtained from the nitrogen &dgr;‐doped layers is investigated in detail, and a deep acceptor and a deep donor with ionization energies of ∼170 and ∼88 meV are reported for the nitrogen &dgr;‐doped layers. These two deep centers are assigned to N clusters, i.e., NSe‐Zn‐NSefor the deep acceptor and NSe‐NZnfor the deep donor. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115091

出版商:AIP    

年代:1995

数据来源: AIP