摘要:

The effects of sputter etching and subsequent surface treatments including thermal annealing and oxygen exposure onn‐InP surfaces have been studied by measuring the photoemission spectra using both Al K&agr; and synchrotron radiation. Results indicate that sputtering with Ar+at 1–3 keV and low current density leaves an In‐rich surface (In/P=2) and, from the movement of the Fermi level relative to the conduction‐band minimum, is seen to introduce acceptor‐type defects. Annealing of the surface causes dissolution of some excess In into the bulk as well as removal of some of these defects. The behavior of the annealed surface to oxygen exposure is similar to that of the cleaved surface with the creation of donor defects.

ISSN:0003-6951    

DOI:10.1063/1.98914

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Here we present the first report of electrical transport measurements (Hall effect and Shubnikov de Haas) on modulation‐doped InP/In0.53Ga0.47As multiquantum wells grown by atmospheric pressure metalorganic chemical vapor deposition. Measurements were made on samples containing from 4 to 50 doped quantum wells. The carrier density per well was observed to be constant, approximately 1×1012cm−2independent of the number of wells, with 4 K mobilities from 70 000 to 90 000 cm2 V−1 s−1. Very little persistent photoconductivity was observed in any of the multiple quantum well structures.

ISSN:0003-6951    

DOI:10.1063/1.98915

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Cathodoluminescence and electroacoustic detection have been used for the characterization of Be‐doped GaAs epilayers grown by molecular beam epitaxy for the doping levels greater than 6.5×1017at. cm−3. The Be concentration dependence of cathodoluminescence intensity as well as electron acoustic intensity shows the presence of nonradiative centers for concentrations greater than 1018at. cm−3. Besides, extended defects and doping striations are revealed by electron acoustic images for heavily Be‐doped GaAs (1020at. cm−3).

ISSN:0003-6951    

DOI:10.1063/1.98916

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An enhanced‐overpressure capless annealing technique suitable for annealing ion‐implanted InP at temperatures of 900 °C is described. The technique utilizes a Sn‐coated InP wafer and is based on the same principle as the In‐Sn‐P liquid‐solution method for eliminating InP surface degradation prior to epitaxial growth. InP samples implanted with 140 keV, 1014cm−2Si+and annealed at 900 °C for 10 s exhibited improved electrical characteristics over samples annealed at 750 °C for 5 min using conventional encapsulation techniques.

ISSN:0003-6951    

DOI:10.1063/1.98917

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Solid‐state interface reactions between metal thin films and (100) GaAs substrates at elevated temperatures are studied by conventional and heavy‐ion Rutherford backscattering spectrometry, x‐ray diffraction, and transmission electron microscopy. Metals investigated in this study include Pt, Pd, Ni, Co, Rh, and W. Electrical properties of the metal/n‐GaAs diodes undergoing annealing treatments at various temperatures were also measured with the current‐voltage dependence. Optimum diodes with maximum barrier heights as well as minimum leakage currents are obtained for diodes annealed at temperatures at which a uniform thin layer of reacted phase is observable at the interface. The barrier heights of the optimum diodes show a linear dependence on the work functions of the various metals. The range of these barrier heights is limited by nonstoichiometry related defects as suggested by a recently proposed amphoteric native defect model.

ISSN:0003-6951    

DOI:10.1063/1.98918

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A bevel has been etched in a GaAs epitaxial film grown on a Si substrate, so that the Raman spectrum of the GaAs layers can be measured as a function of distance from the GaAs/Si interface. The amount of strain and disorder in the GaAs film has been estimated from the GaAs longitudinal optical phonon line shape and frequency. Both the strain and the amount of disorder were found to decrease with increase in the distance from the interface.

ISSN:0003-6951    

DOI:10.1063/1.98919

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The electrical characteristics of Al/ZnS/p‐Si diodes have been investigated. The behavior is shown to be very similar to that of the tin oxide /ZnS/p‐n+diodes used previously for electroluminescent diodes indicating that current through the ZnS is limited by the rate of generation of minority carriers in thep‐Si. The fact that the current is limited is the surest indication that no breakdown is occurring either in the ZnS or the silicon. These results are discussed, both in the context of device manufacture and in the context of a recent theory of breakdown in electroluminescent diodes.

ISSN:0003-6951    

DOI:10.1063/1.98920

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have measured the effective dynamic viscosity of molten GaAs and InSb as a function of axial magnetic field by the oscillating vessel method. Effective viscosity of these semiconductor melts is observed to increase with the axial magnetic field intensity in the range of 0 to 5 kG.

ISSN:0003-6951    

DOI:10.1063/1.98921

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have fabricated superconducting quantum interference devices (dc SQUID’s) from thin films of the superconducting oxide YBa2Cu3Oy. The devices were made by first lithographically patterning an ion implant mask containing a 40 by 40 &mgr;m loop and two 17‐&mgr;m‐wide weak links over a ∼1‐&mgr;m‐thick oxide film. Ion implantation was then used to destroy the superconductivity in the film surrounding the device without actually removing material, resulting in a completely planar structure for the SQUID’s. The SQUID’s were operated in the temperature range from 4.2 to 68 K. The superconducting flux quantum was measured to beh/2ein these materials.

ISSN:0003-6951    

DOI:10.1063/1.98922

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Commercially useful, bulk superconductors typically require stabilization using a normal metal cladding for reasons of electrical, thermal, and mechanical protection and, in general, need to be drawn into fine fibers and wound into a magnet configuration. The recent discovery of high‐TCsuperconductor materials such as Ba2YCu3O7stimulated worldwide interest in the subject, however, with much concern about fabricability of such brittle ceramic materials into desirable fine wire geometry. In this letter, we report preliminary success in the fabrication of fine‐wire, composite superconductors consisting of a high‐conductivity normal metal shell such as Ag or Cu/Ni/Au and a superconducting core of Ba2YCu3O7oxide. The wire is would into a coil, and then heat treated to produce the desired chemistry in a dense structure. The resistivity of the composite wire is measured to be zero at ≊90 K (in zero field) with a zero‐field critical density of ≊175 A/cm2. Microscopy and x‐ray analysis show that the superconducting core is continuous, and retains phase composition after wire drawing and heat treatment. These results demonstrate the feasibility of producing superconducting ceramic composite wire, although the practical applications must await the resolution of many practical problems and reliability issues.

ISSN:0003-6951    

DOI:10.1063/1.98923

出版商:AIP    

年代:1987

数据来源: AIP