摘要:

We report a study of transport in crossed electric and magnetic (B) fields in a double‐barrier tunneling structure with a wide (600 A˚) well atT=1.5 K and 0<B<23 T. AtB=0 we observe 21 resonances, 11 of which correspond to extended‐state resonances for biases >0.85 V. Under a transverse magnetic field, the bound resonances evolve into magnetoelectric states and are shifted to higher biases. In the low bias range, for high magnetic fields, additional resonances from barrier‐bound skipping states are observed. A semiclassical model for ballistic motion in crossed fields is used to determine boundaries between the different trajectory regimes (i.e., traversing, skipping, bulk‐like) in the magnetic field‐bias voltage space of the resonances. The model shows excellent quantitative agreement with experiment when nonparabolic corrections to the effective mass are included. In addition, theB‐induced shift in the transition from bound to extended‐state tunneling resonances is explained with this simple description.

ISSN:0003-6951    

DOI:10.1063/1.103095

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

High quality, epitaxial, relaxed GexSi1−xlayers have been grown by rapid thermal processing chemical vapor deposition. Relaxation is believed to be due primarily to the high deposition temperature of 1000 °C and occurred through the formation of an asymmetric misfit dislocation network aligned along the ⟨110⟩ directions and confined to the interface. The only other defects observed were single threading dislocations at the ends of misfit dislocations.

ISSN:0003-6951    

DOI:10.1063/1.103096

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Shallown+‐pjunctions were formed by utilizing aninsitudoped thin polycrystalline silicon layer as a diffusion source. Theinsituarsenic‐doped polycrystalline silicon films were deposited by rapid thermal processing chemical vapor deposition. The dopant pileup phenomena were observed at both the polycrystalline silicon/silicon interface and at the surface. The dopant concentrations were higher when the deposition temperatures were lower. The observed pileup phenomena at the polycrystalline silicon/silicon interface were temperature dependent and mainly due to the segregation of arsenic at the grain boundary. The dopant distribution was mainly due to the grain boundary diffusion and grain growth mechanisms. Extremely shallown+‐pjunctions were achieved and laterally uniform delineated junctions were observed. The dopant concentration in the Si substrate drops two orders of magnitude in less than 500 A˚.

ISSN:0003-6951    

DOI:10.1063/1.103097

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have deposited diamond films with micron‐size crystals on Si⟨111⟩ using low‐pressure hot‐filament‐assisted chemical vapor deposition. These films have been characterized by positron annihilation, Raman spectroscopy, scanning electron microscopy, and x‐ray photoelectron spectroscopy. In addition to the results for the electronic structure and morphology, we also present new results for the lattice defects present in these films.

ISSN:0003-6951    

DOI:10.1063/1.103098

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have investigated the lattice location of Sn atoms in Sn‐doped GaAs thin films grown by molecular beam epitaxy using ion channeling techniques. Accumulation of ≊2×1014atoms/cm2of Sn on the GaAs surface was detected. These surface Sn atoms were determined to be randomly distributed within ≊20 A˚ of the surface of the GaAs. Angular scans of the Ga K&agr;, As K&bgr;, and Sn Lx rays across the ⟨100⟩, ⟨110⟩, and ⟨111⟩ axial channels indicated that the Sn atoms in the GaAs layer are mostly substitutional. No displacement of the Sn atoms larger than 0.14 A˚ from the substitutional sites was detected.

ISSN:0003-6951    

DOI:10.1063/1.103099

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of implantation damage on B diffusion are analyzed through the use of29Si implants. Implant doses of29Si ranging from 1×1012/cm2to 1×1014/cm2were used to create controlled amounts of damage. Temperatures ranging from 800 to 1000 °C were used to anneal the implant damage. For all anneal temperatures, the peak B concentration was well below the intrinsic electron concentration. Even for29Si doses as low as 1×1012/cm2significantly enhanced B diffusion was observed. The largest enhancement in B diffusion was observed for the highest29Si implant dose and lowest anneal temperature. The kinetics of damage annealing determine the transient enhancement in the B profile. These results have important implications for the formation of shallow junctions using ion implantation.

ISSN:0003-6951    

DOI:10.1063/1.103100

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Problems associated with quantum mechanical reflection of miniband carriers at the ends of superlattices are examined. Mo¨bius transformations which map miniband Bloch wave reflectivity into plane wave reflectivity and vice versa are derived. These transformations facilitate the design of blocking and antiblocking layers which are analogous to reflective and antireflective coatings on optical elements. An example of termination layer design which is easy to implement is given. Applications include superlattice infrared detector design.

ISSN:0003-6951    

DOI:10.1063/1.103101

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We show that the current‐voltage characteristics of resonant tunneling structures are drastically influenced by the difference of electronic effective masses between the electrodes and the quantum well. In particular, if the mass in the well is larger than that in the emitter, the current peak is shifted to lower voltages, relative to the more conventional case of equal masses. This situation is illustrated experimentally with GaAs/AlAs/GaAs heterostructures, in which &Ggr; electrons emitted from GaAs tunnel resonantly through the AlAsXpoint, where the mass is considerably heavier.

ISSN:0003-6951    

DOI:10.1063/1.103102

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Room‐temperature MeV Au++implantation into silicon with energies above 1.8 MeV shows a splitting of the Au concentration profile in the Rutherford backscattering spectrometry (RBS) spectra. Cross‐section transmission electron microscopy micrographs show two distinct regions of Au precipitates corresponding to the peaks in the RBS spectra. The double peaks can be explained by the segregation of Au into the highly damaged region near the end of the implant range and Au segregation along a dislocation network. These dislocations arise from dynamic beam annealing during the implant and act as paths for rapid diffusion. Precipitation occurs when the Au concentration exceeds the solubility limit. Lower energy implants resulted in the expected Gaussian distributions.

ISSN:0003-6951    

DOI:10.1063/1.103103

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

For the first time, fabrication of high‐temperature superconducting Tl‐Ca‐Ba‐Cu‐O (TlCaBaCuO) thin films on LaAlO3substrates is reported. TlCaBaCuO thin films were deposited by rf magnetron sputtering of a single composite powder target in a pure argon plasma. The films were sintered in an excess thallium ambient at 850 °C for 15 min followed by a 30 min oxygen annealing at 750 °C. Scanning electron microscopy and x‐ray diffraction results showed the smooth and highlyc‐axis oriented nature of the thin films. The temperature dependence of resistance showed the onset of critical transition temperature (Tc) at 114 K, and zero resistance at 103 K.

ISSN:0003-6951    

DOI:10.1063/1.103104

出版商:AIP    

年代:1990

数据来源: AIP