摘要:

The dynamic behavior of ferromagnetic cobalt granules in ion‐beam cosputtered Co22Ag78samples under annealing treatment was examined by transmission electron microscopy (TEM), using a real‐time video recording system. Cobalt granules about 10 nm in average size were embedded in a nonmagnetic silver matrix. It was observed that,insitu, the cobalt granules changed continually in shape and size with annealing temperature and time. We have estimated the changes of cobalt granule size from the results of TEM. The ferromagnetic resonance method was employed to study the evolution of the shapes of cobalt granules. It shows that cobalt granule shapes and sizes change mainly along the plane of the film during the process of annealing. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114772

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report here an anomaly that the photorefractive phase conjugate reflectivity increases sharply near 55, 70, and 110 °C in three different doped‐LiNbO3crystals. The anomalous phenomenon is possibly concerned with the structural phase transformation of the crystal, which induces an extra internal electric field and enhances the reflectivity. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114773

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Interface recombination in GaAs at the GaAs/AlAs interface has been investigated before and after selective ‘‘wet oxidation’’ of the AlAs layer. Time‐resolved photoluminescence of the band‐edge GaAs emission has been used to characterize the interface recombination. Prior to oxidation, the interface recombination is low. After oxidation, the interface recombination has greatly increased, and is comparable to a free GaAs surface in air. However, isolating the GaAs layer from the oxide by a 30 nm layer of Al0.3Ga0.7As allows the interface recombination to remain low after the oxidation. These results help explain the low threshold currents which have been observed in vertical cavity lasers which use wet oxidation of AlAs for current confinement. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114774

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Low energy and low dose B+‐implanted Si has been studied using transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS). Czochralski‐grown (100) Si wafers were implanted with 4 keV B+to a dose of 1×1014/cm2. Subsequently, anneals were performed between 700 and 800 °C for times between 15 s and 8 h in an ambient atmosphere of N2. SIMS results show transient enhanced diffusion (TED) of the boron that saturates in less than 15 min for all annealing temperatures studied. TED results in an increase in the junction depth by at least 60 nm at a 1×1016/cm3concentration. TEM studies show that, even for the shortest times before TED is observed, {311} defects are not detected. These results imply that there may be more than one source of interstitials for TED. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114775

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Large‐area GaN photovoltaic structures withp‐njunctions have been fabricated using atmospheric pressure metalorganic chemical vapor deposition. The photovoltaic devices typically exhibit selective spectral characteristics with two narrow peaks of opposite polarity. This can be related top‐njunction connected back‐to‐back with a Schottky barrier. The shape of the spectral characteristic is dependent on the thickness of then‐ andp‐type regions. The diffusion length of holes in then‐type GaN region, estimated by theoretical modeling of the spectral response shape, was about 0.1 &mgr;m. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114776

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The contribution of more than one carrier to the conductivity in modulation‐doped field effect transistors (MODFET) affects the resultant mobility and complicates the characterization of these devices. Mixed conduction arises from the population of several subbands in the two‐dimensional electron gas (2DEG), as well as the presence of a parallel path outside the 2DEG. We characterized GaAs/AlGaAs MODFET structures with both delta and continuous doping in the barrier. Based on simultaneous Hall and conductivity analysis we conclude that the parallel conduction is taking place in the AlGaAs barrier, as indicated by the carrier freezeout and activation energy. Thus, simple Hall analysis of these structures may lead to erroneous conclusions, particularly for real‐life device structures. The distribution of the 2D electrons between the various confined subbands depends on the doping profile. While for a continuously doped barrier the Shubnikov–de Haas analysis shows superposition of two frequencies for concentrations below 1012cm−2, for a delta doped structure the superposition is absent even at 50% larger concentrations. This result is confirmed by self‐consistent analysis, which indicates that the concentration of the second subband hardly increases. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115068

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The crystal damage in optoelectronic devices caused by dry etching methods [ion beam etching, reactive ion etching, etching with plasmas excited by electron cyclotron resonance (ECR)] was evaluated. The analytics applied are photoluminescence and Fabry‐Perot damping measurement which were applied to waveguides. A significant improvement is observed using ECR etching as low damage combined with high etching rates is concerned. To evaluate a method as soft or hard etching, Fabry‐Perot damping measurement has emerged to be the most discriminate and decisive tool. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115069

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have performed lateral diffusion measurements of photo‐excited electron‐hole pairs in a GaAs/AlAs multiple quantum well structure under magnetic fields applied perpendicular to the wells, by using an all‐optical time‐of‐flight technique with a single‐mode optical fiber probe. Remarkable suppression of exciton diffusion is observed, and is ascribed to the magnetic perturbation by which moving excitons are affected proportionally to the square of wave vectors. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115070

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A fundamental issue in silicon selective epitaxial growth (SEG) processes is the impact of the pre‐epitaxy silicon surface treatments and the SEG ambient on the properties of thin insulating materials exposed to the preclean environment. In this study, we compare pinhole formation in 10–50 nm thermal oxides with more robust oxide/nitride composites of similar thickness. The degradation of thin thermal oxide is attributed to pinhole formation and expansion in the ultrathin oxide layers duringexsitupre‐epi surface treatments,insituH2prebake, and selective epitaxial deposition process. The superior resistance of oxide/nitride/oxide (ONO) structures to dielectric degradation may be attributed to the existence of the sandwiched silicon nitride layer which suppresses the mechanism of oxide decomposition during the pre‐epitaxy wet cleaning, and the selective epitaxial growth processes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115071

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A comparative study of the Raman spectra of ZnSe films grown by molecular beam epitaxy on GaAs(100) substrates passivated byNH4)2)SxandS2Cl2solutions is presented. Based on the analysis of the line shape of the first‐order longitudinal‐optical phonon of ZnSe with spatial correlation model of Raman scattering, it is shown that the ZnSe films grown on the GaAs substrates passivated byS2Cl2solutions have longer coherence lengths, which indicate that their crystalline qualities are better than those passivated byNH4)2Sxsolutions. In addition, the barrier heights of ZnSe/GaAs interfaces for different S passivations have been obtained from the ratios of the intensity of the coupled longitudinal‐optical phonon‐plasmon mode to that of the longitudinal‐optical mode of GaAs Raman peak. The results show that the ZnSe/GaAs samples passivated byS2Cl2solutions have lower density of interfacial states. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115072

出版商:AIP    

年代:1995

数据来源: AIP