摘要:

A modulation‐doped system of asymmetric‐coupled quantum wells is shown theoretically to possess a large optical nonlinearity due to the change transfer associated with intersubband transition. The range of parameters leading to optical bistability is detetermined. A novel triple quantum well system is suggested, allowing a few orders of magnitude reduction in switching power density. Novel hybrid optoelectronic devices, incorporating the triple quantum well system into the channel of a modulation‐doped field‐effect transistor, are proposed with potential applications as optoelectronic switches and detectors.

ISSN:0003-6951    

DOI:10.1063/1.101058

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The study of diffusion and drift of Si in AlxGa1−xAs by means of capacitance‐voltage measurements reveals that low substrate temperatures during growth by molecular beam epitaxy are required to achieve &dgr;‐function‐like doping profiles. The diffusion coefficient of Si in Al0.3Ga0.7As is determined. We further show theoretically that the random Poisson distribution (usually assumed for dopant distributions in semiconductors) should be modified at high dopant concentrations due to repulsive interactions of impurities.

ISSN:0003-6951    

DOI:10.1063/1.101059

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

InP samples, which had received a capless anneal in a phosphine/hydrogen atmosphere, were examined for hydrogen contamination by secondary‐ion mass spectrometry. It is found that hydrogen accumulates at the InP surface during annealing. Annealing of Be‐implanted InP leads to similar profile shapes for the Be and H atoms. Passivation of the Be acceptors, if effective at all, appears to be of only minor significance.

ISSN:0003-6951    

DOI:10.1063/1.101060

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The standardn‐type dopant Ga is predicted to change its character from a shallow donor to a deep trap with increasing alloy compositionxin Zn1−xMnxSe. As a result, Ga‐doped Zn1−xMnxSe alloys should bentype for very smallx, but not for Mn‐rich material.

ISSN:0003-6951    

DOI:10.1063/1.101061

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The noise energy of conventional thin‐film dc superconducting quantum interference devices (SQUIDs) flattened out as the operating temperature was lowered below 140 mK. We attribute this saturation to the heating of the electrons in the resistive shunts by the SQUID bias current. This ‘‘hot‐electron effect’’ is a general property of normal metals at low temperatures and arises from the limited rate at which the electrons can transfer energy to phonons. The temperature of the electrons, and hence the noise energy of the SQUIDs, was reduced by a factor of about 3 by attaching large volume ‘‘cooling fins’’ to each shunt.

ISSN:0003-6951    

DOI:10.1063/1.101062

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Improved superconducting and mechanical properties were obtained for Bi(Pb)‐Sr‐Ca‐Cu‐O tapes, prepared by the combined process of doctor‐blade casting, cold rolling, and sintering. The tape has an oriented microstructure with the highTcplate‐like grains having theircaxes perpendicular to the rolling surface. The tape is flexible and can be bent without any degradation ofJcto just before fracture (strain larger than ∼0.12%).

ISSN:0003-6951    

DOI:10.1063/1.101063

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Convenient methods for obtaining extremely low resistivity contacts to bulk highTcsuperconductors ( &rgr;cin the range of 10−11–10−12&OHgr; cm2) are described. Three different configurations of silver contact metal in Y‐Ba‐Cu‐O have been employed, i.e., embedded Ag wire, embedded Ag particles, and selectively patterned Ag clad on superconductor wire. In all three cases, the low‐resistivity metallic contacts are formedinsituduring the sintering or melt processing of the superconductor, thus eliminating the need for separate steps of contact preparation such as vacuum deposition of contact metal and additional heat treatment. The distribution and morphology of the silver contacts will be discussed. The measured contact resistivities in the present work are the lowest reported for the highTcsuperconductors, and these methods may serve as a useful basis for important contact technologies needed for bulk superconductor applications.

ISSN:0003-6951    

DOI:10.1063/1.101038

出版商:AIP    

年代:1989

数据来源: AIP