摘要:

We report the first demonstration of CdTe metal‐semiconductor field‐effect transistors. These transistors were fabricated usingn‐type CdTe films grown by photoassisted molecular beam epitaxy. Using this new film deposition technique, it is possible to obtain highly activatedn‐type orp‐type films suitable for device applications. In the present work, transistor structures with 5 or 100 &mgr;m gate lengths having channel dopings in the range from 2×1016to 2×1017cm−3were fabricated and tested. The 5 &mgr;m gate devices have transconductances as large as 10 mS/mm and pinch‐off voltages of 4.0 V.

ISSN:0003-6951    

DOI:10.1063/1.98805

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have achieved avalanche gain at a wavelength of 10.3 &mgr;m in AlxGa1−xAs/GaAs quantum well superlattices. The photoelectrons are generated by resonant intersubband absorption and tunneling, and then avalanche via hot‐electron impact ionization of carriers out of the quantum wells. Good agreement is obtained between a theoretical calculation of this process and our experiments.

ISSN:0003-6951    

DOI:10.1063/1.98806

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The magnetophotoluminescence peaks in the ‘‘two‐electron’’ satellites of the donor bound exciton transitions corresponding to the shallow donors S, Si, Ge, Sn, and Te have been identified by correlation of photoluminescence measurements with photothermal ionization measurements on the same high‐purity epitaxial GaAs samples. The magnetophotoluminescence measurements were made at 1.7 K and a magnetic field of 9.0 T. These results permit the use of magnetophotoluminescence measurements for the identification of residual donor impurity species in high‐purity GaAs.

ISSN:0003-6951    

DOI:10.1063/1.98807

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have investigated the microstructure and properties of YBa2Cu3O9−&dgr;that contain resistive transitions at 90 and near 290 K using high‐resolution and analytical transmission electron microscopy and Raman scattering techniques. The specimens contain normal orthorhombic (Pmmmspace group) phase associated withTc=90 K, and another phase which we tentatively assign it to be associated with the resistive transitions near 290 K. The new phase has acaxis larger by about 16% and it grows epitaxially on the {100} planes of the orthorhombic (tripled perovskite unit cell) phase havingTc=90 K.

ISSN:0003-6951    

DOI:10.1063/1.98808

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Fabrication of highTcceramic superconductors by an oxide melting method in place of a conventional sintering method has been attempted. Using three different processes, i.e., melt drawing, melt spinning, or preform‐wire melting, it is demonstrated that the Ba2YCu3O7−&dgr;type superconductors can successfully be fabricated into a desired geometry such as wire and ribbon.Tc’s forR=0 were about 92 K. The density of the melt‐processed compound was measured to be as high as 6.2 g/cm3, or ∼98% of the theoretical density 6.3 g/cm3as compared to the value of 80–85% density for sintered samples. The increased density is likely to be responsible for the noted improvements in fracture resistance and in theJcvalue of the melt‐processed compound.

ISSN:0003-6951    

DOI:10.1063/1.98809

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

YBaCuO superconducting thin films were prepared by multilayer deposition on different kinds of substrates. HighTcwith an onset of 94 K and a zero resistance at 84 K has been obtained by deposition on pure ZrO2substrates. The nature of zero resistance as well as thedR/dTcharacteristic aboveTcand the influence of substrates are discussed.

ISSN:0003-6951    

DOI:10.1063/1.98810

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A model is proposed for a novel surface‐to‐surface segregation process which would be observed during growth by vapor deposition of thin polycrystalline films of alloys exhibiting classic surface segregation. The model depends on sufficient surface mobility to allow equilibration between surfaces of different grains and insufficient bulk mobility to allow equilibration between the surface and bulk of each grain before the present surfaces are covered by the next layer of material. This high ratio of surface to bulk mobility is easily found under standard deposition conditions. The model leads to an inhomogeneous film in which the composition of each grain is dependent on its crystallographic orientation.

ISSN:0003-6951    

DOI:10.1063/1.98811

出版商:AIP    

年代:1987

数据来源: AIP