摘要:

In this letter, we report the observation of the enhanced electron mobility in three different Al0.08Ga0.92N/GaN heterostructures. These structures were deposited on (0001) 6H-SiC substrates by using the low-pressure metalorganic chemical vapor deposition method. The structure was composed of 500 Å AlGaN compositional stair-step layer deposited onto 1.3&mgr;m GaN epitaxial layer. There is a 100 Å GaN Cap layer on top of the AlGaN layer to prevent the oxidation of the AlGaN layer. By using the van der Pauw method of Hall measurement, the sheet carrier density and mobility for Al0.08Ga0.92N/GaN heterostructure are 6.6×1012cm-2and 5413 cm2/Vs at 77 K, respectively. This high value of mobility is, to the best of our knowledge, the first observed two-dimensional electron gas (2DEG) at the AlGaN/GaN stair-step type of heterostructure. Other interface structures such as graded composition and bulk composition structures were also prepared and 2DEG properties were observed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118940

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

InAs nanocrystals embedded inSiO2matrix have been fabricated by a radio-frequency magnetron co-sputtering technique without postannealing. X-ray photoelectron spectra and Raman spectroscopy strongly suggest the existence of InAs nanocrystals in theSiO2matrix. From the optical absorption spectrum, the absorption edge exhibits a very large blueshift of 3.3 eV with respect to that of bulk InAs. The double-peak ultraviolet photoluminescence is observed. Our experimental results show that this double-peak phenomenon originates from the radiative recombination of the quantum-confined electron-heavy hole excitons and electron-split-off hole excitons. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118926

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have investigated thein situchemical beam etching (CBET) process of (Al)GaAs using tris-dimethylaminoarsenic (TDMAAs) within a chemical beam epitaxy chamber. The optimal CBET condition of (Al)GaAs is established, according to the analysis of atomic force microscopy, capacitance–voltage carrier profiles, and current–voltage(I–V)measurements. This CBET process using TDMAAs is shown to provide a good etching selectivity (>20) of GaAs overAlxGa1−xAs(x⩾0.35)with a very smooth etched surface at the nanometer scale and a clean etched/regrown interface for regrowth applications. ImprovedI–Vcharacteristics of etched/regrownp-nAlxGa1−xAs(x⩽0.35)junctions is also successfully demonstrated when the GaAs cap layer is preferentially etched first by TDMAAs before regrowth ofAlxGa1−xAs.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119087

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The ability to form low resistance Ohmic contacts to InAlN using refractory metallization on In-containing contact layers has been investigated. The crystal quality as measured by surface roughness and x-ray diffraction was found to be a determining factor in the contact resistance which could be obtained usingWSixcontacts. InN growth conditions which resulted in poorer structural quality, such as the use of GaAs rather than sapphire substrates, low nitrogen flows, and low growth temperatures, resulted in contact resistances of10−4–10−3 &OHgr; cm2, as compared to∼10−5 cm2for InAlN alone. Using optimized conditions, contact resistances to InAlN of∼3.5×10−6 &OHgr; cm2were obtained. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118927

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new method to determine the off-diagonal element of the dielectric tensor from the measurements ofp- ands-wave Kerr rotation angles, without measuring the ellipticity is reported on in this letter. The method has been verified by determining the off-diagonal elements of Cu/Co multilayer having in-plane magnetization and Co/Pd multilayer having perpendicular magnetization. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118928

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Magnetic resonance force microscopy (MRFM) is a new microscopy technique that combines the spin selective detection of nuclear or electron spin resonance with the high spatial resolution of atomic force microscopy. In this letter we present MRFM measurements on a three-layer system in the micron range. We detected the one-dimensional distribution of proton spins in a sample that consisted of two-ammonium sulphate layers and an intermediate layer of sodium chloride. The experiments were done at room temperature and normal pressure, in contrast to earlier MRFM measurements that have been carried out in vacuum at room temperature or low temperatures. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.118929

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have fabricated novel magnetostrictive composites consisting ofSmFe2embedded in an Fe or Al matrix which feature high magnetostriction and good mechanical strength. Hot pressed composites of 50&percent;SmFe2/50&percent;Fe or Al by volume have magnetostrictive strains parallel to the applied magnetic field,&lgr;∥,between−280and−440ppm when consolidated at 610 (Fe) or 540 °C (Al). One unique feature of this work is the production of the magnetostrictiveSmFe2component by melt spinning; ribbon-based composites with Al combine significant magnetic coercivity,Hci=3 kOe,with high magnetostriction (&lgr;∥=−280 ppm). Unlike their brittleSmFe2parent materials, the composites are easily machinable. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118930

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

By tailoring the microcrystalline structure of MnBi films, using Al interlayers, a reduction of the high-temperature coercivity by a factor of 3 is achieved. The separation of Bi/Mn bilayers by Al interlayers acts as a diffusion barrier perpendicular to the surface. After annealing, the MnBi layers contain single-domain particles surrounded by an Al matrix exhibiting no significant increase of the coercive field with increasing temperature. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118931

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Finite element modelling was applied to the bending behaviour of a cantilever coated with a magnetostrictive film. The model is verified by comparison with accepted analytical solutions, then extended to the more realistic case in which one end of the cantilever is rigidly clamped across the width. It is shown that the central deflection of the end of the cantilever is a function of the geometric aspect ratio. An empirical correction factor is suggested to account for this variation. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118932

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We show that shape anisotropy can be used to control the response characteristics of magnetic tunnel junctions. By varying the junction shape, the resistance versus field curve was made to vary from a nonhysteretic linear curve with a high-field sensitivity (0.3&percent;/Oe) to a hysteretic response curve with high squareness. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118933

出版商:AIP    

年代:1997

数据来源: AIP