摘要:

Knowledge of the Hg(3P1) spatial distribution in Hg rare gas low pressure discharges is important for understanding radiation transport, and aids in the formulation of discharge models for fluorescent lamps. We report on a novel single laser, two intersecting beams technique, which, for the first time, yields pinpoint information on the radial density profile of excited state mercury in the discharge positive column. Advantages over conventional single beam absorption are discussed, and preliminary data for a discharge containing one isotope (198Hg) of mercury and 2.5 Torr argon are presented.

ISSN:0003-6951    

DOI:10.1063/1.98024

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A tungsten silicide/polycrystalline silicon composite gate structure has been fabricated in which tungsten silicide layers on polycrystalline silicon have been deposited by the low‐temperature chemical vapor deposition method (at 360 °C) using a WF6/SiH4gas mixture. The fluorine distributions in this structure have been studied by secondary ion mass spectrometry. In samples with as‐deposited tungsten silicide, it has been confirmed clearly that almost all of the fluorine resides in the silicide layer. After high‐temperature annealing (above 950 °C), however, fluorine is found to diffuse easily into the gate SiO2through the polycrystalline silicon, that is, the gate oxide has been changed into the fluorine‐doped oxide.

ISSN:0003-6951    

DOI:10.1063/1.98025

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

High resolution, energy dispersive patterns are obtained with parallel beam x‐ray optics, synchrotron radiation, a step scanning incident beam channel monochromator, and independently selectable specimen and detector angles, which are fixed during the scan. This permits decoupling of the specimen and detector geometry (which would cause defocusing in conventional methods) and makes it possible to measure the intensities at several incidence angles to determine the preferred orientation of the crystallites in a thin film. The method is illustrated by patterns of a Pd/Xe thin film.

ISSN:0003-6951    

DOI:10.1063/1.98026

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Arsenic‐doped CdTe layers have been grown by organometallic vapor phase epitaxy in an atmospheric pressure reactor using arsine as the dopant gas. Doping levels above 2×1017cm−3have been reproducibly obtained for the first time in an epitaxial growth system, with a doping uniformity of ±20% over 1.5×1.5 cm. This is a much higher level of doping than usually possible in bulk growth systems. The layers were characterized by photoluminescence measurements at 12 K and by Hall measurements as a function of temperature. The ionization energy of the As acceptor was found to be about 62±4 meV from transport measurements. It was also shown that the electronic activity of the As incorporated is a function of the dimethylcadmium to diethyltelluride partial pressure ratio in the gas phase.

ISSN:0003-6951    

DOI:10.1063/1.98027

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

X‐ray diffraction has been used to study CdTe layers grown by molecular beam epitaxy on Cd0.96Zn0.04Te or InSb substrates with either (111) or (001) orientation. The layers are elastically strained up to a critical thickness, above which misfit dislocations are generated. Our experimental determinations of the critical thickness and the relaxation of the stress while increasing the layer thickness are different from predictions of the existing models. We present a discussion of relaxation based on the determination of the minimum energy state of the layer for a given thickness. We show that above the critical thickness, the layer relaxes so that the product of the stress by the thickness remains constant. This constant has been experimentally determined for both (111) and (001) orientation.

ISSN:0003-6951    

DOI:10.1063/1.98261

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The conduction‐band discontinuity &Dgr;Ecand interface charge density &sgr; have been studied for GaAs/In0.5(Ga1−xAlx)0.5P heterojunctions, prepared by metalorganic chemical vapor deposition. The dependences of &Dgr;Ecand &sgr; on Al compositionxwere investigated forxfrom 0 to 1. The In0.5Al0.5P/ In0.5Ga0.5P heterojunction was also examined. The results suggest that the valence‐band discontinuity &Dgr;Evfor GaAs/In0.5(Ga1−xAlx)0.5P is a linear function ofxand is larger than &Dgr;Ec, being in reasonable agreement with results on the InAlP/InGaP heterojunction. The &sgr; values for GaAs/InGaAlP were found to be one order of magnitude larger than those for GaAs/AlGaAs and InAlP/InGaP heterojunctions.

ISSN:0003-6951    

DOI:10.1063/1.98028

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

This letter deals with the atomically flat interfaces at GaAs/AlGaAs heterojunctions grown by a modified metalorganic chemical vapor deposition, flow‐rate modulation epitaxy. Single quantum wells show low‐temperature photoluminescence with narrower linewidths than those grown by conventional metalorganic chemical vapor deposition. An x‐ray diffraction spectrum of (GaAs)2(AlAs)2superlattices exhibits no forbidden (003) and (001) diffractions, suggesting that the interfaces are fairly flat.

ISSN:0003-6951    

DOI:10.1063/1.98029

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Evidence is presented to show that the degradation of near‐band‐gap photoluminescence emission in GaAs with time of exposure to low power, cw laser excitation can be attributed to a surface mechanism that is independent of surface oxidation and may involve an interaction between crystal point defects and the photogenerated electron‐hole plasma near the surface.

ISSN:0003-6951    

DOI:10.1063/1.98030

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Tuning of the optical absorption coefficient by electrical bias in doping superlattices (n‐i‐p‐icrystals) is demonstrated for the first time by both photoconductivity and transmission measurements at room temperature. The absorption coefficient at 1.04 &mgr;m obtained from the photoconductivity measurement varies by a factor of 240 when thep‐njunction bias is changed from 0.4 to −1.5 V. A change of transmission up to 22% at 0.89 &mgr;m wavelength through a 2.1‐&mgr;m‐thickn‐i‐p‐icrystal is achieved by varying bias merely between 0.6 and −2.0 V. Moreover, the change of transmission is nearly linear withp‐njunction bias.

ISSN:0003-6951    

DOI:10.1063/1.98031

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An analysis of the hydrogen concentration profiles obtained from secondary ion mass spectrometry in boron‐doped silicon points to a deep donor hydrogen state located ∼0.1 eV above the Fermi level for intrinsic material. The theoretical model takes into account both neutral and ionized hydrogen diffusion, the latter enhanced by a built‐in electric field associated with the hydrogen doping gradient. The activation energies for the two diffusion processes are ∼1.2 and ∼0.8 eV, respectively. A formerly reported discrepancy between low‐ and high‐temperature results is lifted.

ISSN:0003-6951    

DOI:10.1063/1.98032

出版商:AIP    

年代:1987

数据来源: AIP