摘要:

Tuning of the propagation constant difference &Dgr;&bgr;=&bgr;TM−&bgr;TEin single‐mode symmetrical yttrium iron garnet (YIG) film waveguides over a range of 250°/cm by means of external stress is demonstrated. Anaposteriori, precise setting of phase match &Dgr;&bgr;→0, which is a precondition for nonreciprocal mode coupling type components, can be achieved by this method.

ISSN:0003-6951    

DOI:10.1063/1.97235

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Regenerative amplification of temporally compressed picosecond pulses is demonstrated in neodymium: yttrium aluminum garnet (Nd:YAG) at 2 kHz. The seed to the regenerative amplifier originates from a chirped cw mode‐locked Nd:YAG laser pulse. The initial 100 nJ ∼80 ps full width at half‐maximum pulses are amplified and temporally compressed to ∼200 &mgr;J/pulse at a repetition rate of 2 kHz with a pulse width of 12 ps.

ISSN:0003-6951    

DOI:10.1063/1.97621

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We describe an experimental method to detect and measure a thin air gap between an opaque film and a substrate. The method is pulsed photothermal radiometry with signal shape analysis at suitable delayed times. This relies on the use of a short light pulse to heat up the surface of the opaque film by∼10 °C, and detecting the infrared thermal emission from the surface as a function of time for a sufficiently long time. A numerical computation as well as an analytical approximation is developed to explain the dependence of the photothermal radiometry signal shape on the air gap thickness in the range of ten to hundreds of microns. Our work has applications not only for detecting subsurface air gaps and delaminations, but also for measuring the thermal resistance between layers for nondestructive characterization of adhesion bond strengths.

ISSN:0003-6951    

DOI:10.1063/1.97236

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The microstructure of thin layers of GaAs grown on Si substrates at low growth temperatures by molecular beam epitaxy was examined using transmission electron microscopy and MeV4He+ion channeling angular scan analysis. Crystalline island formation is observed at temperatures as low as 325 °C, with epitaxial orientation and distinct nucleation habits apparently tied to the symmetry of the misoriented substrate. For films with no exposure to temperatures above 405 °C, the planar strain is found to be compressive, up to a thickness of 100 nm.

ISSN:0003-6951    

DOI:10.1063/1.97237

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The observation of a variant of the SiE’center which is possibly unique to thin films of SiO2is reported. This center which has not been reported for bulka‐SiO2is detected after x irradiation of films grown on (111) and (100) wafers of silicon. The center contains two threefold coordinated Si atoms with one having axial symmetry and the other having orthorhombic symmetry. Evidence indicates that this defect is very near the Si‐SiO2interface. The annealing behavior of the defect has a bias dependence which is very similar to that observed for fixed oxide charge in metal‐oxide‐semiconductor devices.

ISSN:0003-6951    

DOI:10.1063/1.97238

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Striking effects of dopant atoms on the formation of Ni silicides were observed. Epitaxial NiSi2was found to grow on both BF+2‐ and B+‐implanted (001) and (111)Si at 250–280 °C. The formation of Ni2Si was suppressed. It is conjectured that the presence of dopant atoms may lower the activation energy substantially to promote the formation of epitaxial NiSi2at low temperatures. The effects may be exploited to grow other epitaxial silicides on silicon at low temperatures.

ISSN:0003-6951    

DOI:10.1063/1.97239

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Interference peaks in double‐crystal x‐ray rocking curves have been observed in GaAlAs laser structures. The interference has been shown to arise from phase coherence of the x‐ray waves across a thin heteroepitaxial layer sandwiched between two layers of equal composition. It is shown that the interference fringes can be used to measure active layer thicknesses to ±200 A˚. This is despite the fact that the active layer peak cannot be resolved in the rocking curve.

ISSN:0003-6951    

DOI:10.1063/1.97240

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

In this work, we report on the effect of annealing on the distribution of indium in the surface region of In‐alloyed GaAs crystals. Auger, secondary ion mass spectroscopy, and photoluminescence were used as the analytical tools. It is shown that In migrates and piles up over a depth of several tens or a few hundreds of angstroms from the surface leaving behind an In‐depleted region. The In redistribution results in modifications of the band gap in the surface region of annealed GaAs:In substrates; these modifications take place even at temperatures as low as 400 °C.

ISSN:0003-6951    

DOI:10.1063/1.97241

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

By optimizing its structure, we have improved the current gain and collector‐current peak‐to‐valley ratio of a resonant tunneling hot‐electron transistor. The device has an asymmetric resonant tunneling barrier with an optimal well thickness to attain a higher peak‐to‐valley ratio for the collector current. Also, the device uses a graded collector barrier and decreased base thickness, exhibiting a common emitter current gain of 5.1 (at 77 K), the highest value ever reported for an AlGaAs/GaAs hot‐electron transistor.

ISSN:0003-6951    

DOI:10.1063/1.97242

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new approach to the lateral confinement of electrons in the two‐dimensional electron gas of GaAs‐AlGaAs heterojunctions has been developed. The electrons are electrostatically confined by a shallow mesa structure etched in the uppern‐doped AlGaAs layer. This structure is fabricated using electron beam lithography and reactive ion etching. The undoped AlGaAs spacer layer is not removed in order to avoid mobility degradation and channel depletion. Long narrow channels have been made for the study of electrical transport properties. The effective channel width in the submicron range is smaller than the width of the mesa structure. Preliminary low‐temperature magnetoresistance data are presented.

ISSN:0003-6951    

DOI:10.1063/1.97243

出版商:AIP    

年代:1986

数据来源: AIP