摘要:

The dependence of electron mobility &mgr; on temperatureTin GaAs and AlxGa1−xAs indicates that for compensated material a term having &mgr;∝T−1/2causes a significant reduction in the mobility measured at high temperatures. The magnitude of theT−1/2term in mobility, denoted &mgr;CA, is found to be linearly proportional to the compensating acceptor concentration over a range of more than two orders of magnitude in samples with no intentional doping where carbon is the major compensating acceptor. Intentional compensation using Ge and Zn is found to have no effect on &mgr;CA. Illumination (h&ngr;≳EG) has no effect on &mgr;CA. Such illumination is demonstrated to significantly reduce the size of space‐charge layers at then‐iinterface. Thus, theT−1/2mobility isnotdue to scattering by space‐charge regions as has been previously assumed. The acceptor C, or an associate involving C, is concluded to be the scattering center responsible for &mgr;CA. The effect may be due to the short‐range central‐cell potential resulting from the large electronegativity difference between C and the As for which it substitutes in the lattice.

ISSN:0021-8979    

DOI:10.1063/1.328083

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Long exposure to light decreases the photoconductivity and dark conductivity of some samples of hydrogenated amorphous silicon (a‐Si : H). Annealing above ∼150 °C reverses the process. The effect occurs in the bulk of the films, and is associated with changes in density or occupation of deep gap states. High concentrations of P, B, or As quench the effect. Possible models involving hydrogen bond reorientation at a localized defect or electron‐charge transfer between defects are discussed. An example is shown where these conductivity changes do not affect the efficiency of an a‐Si : H solar cell.

ISSN:0021-8979    

DOI:10.1063/1.328084

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Conductivity measurements on epitaxially grown silicon‐dopedn‐Ga1−xAlxAs as a function of Al concentrationx, for 0.10⩽x⩽0.65 are presented. Simple two‐probe measurements were made possible by the development of a low‐resistance Ohmic contact, with the contact resistance independent ofx. A calculated three band (&Ggr;,X, andL) conductivity of Ga1−xAlxAs as a function ofxshows good agreement with the experimental results. The transition from a direct band‐gap semiconductor to an indirect one occurs atxc=0.45 at 300 °K. The device performance, however, begins to be affected at much lower Al concentration.

ISSN:0021-8979    

DOI:10.1063/1.328085

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Simultaneous measurements of the dielectric loss tangent (tan&dgr;) and thermoluminescence (TL) or of thermally stimulated current (TSC) and thermoluminescence have been carried out in order to study electron trapping phenomena in polyethylene‐terephthalate (PET). Close correlations between the various measurements have been observed. In tan&dgr; measurements made at 1 kHz and at temperatures ranging from −190° to 150 °C four peaks are observed, viz., at −140° ( &bgr;3), −110° ( &bgr;2), −40° ( &bgr;1), and 150 °C (&agr;). Correlations between the simultaneous measurements of TL and tan&dgr; and that of TL and TSC indicate that the electrons are mainly liberated from their traps by the &bgr;1relaxation. Comparison with available dielectric loss data of oligoethylene‐terephthalate suggests that the &bgr;1relaxation of PET should be attributed to the motions of the carboxyl groups in the main chains. Photoelectroluminescence (PEL) for PET has been observed and degradation of the sample has been noted at the luminous region of the PEL. The coincidence of the PEL spectrum with that of TL suggests that the luminescence center should be attributed to that part of the polymeric chains which are liable to chain scission.

ISSN:0021-8979    

DOI:10.1063/1.328086

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Field effect and thermoelectric power measurements have been made as a function of temperature on a series of B doped amorphous silicon samples prepared by glow discharge decomposition of silane. The investigation complements an earlier one on As doped amorphous silicon prepared by the same method. Incorporation of boron leads to an increase in the density of localized states lying 0.42 eV above the valance edge. The density of surface states is less than or equal to 1.5×1011cm−2 eV.−1Electrical transport is interpreted in a two channel model, involving transport both in extended valence states and in a band of localized states associated with the B acceptors. The effect of hydrogen evolution due to thermal annealing on the localized state densities and transport processes is also investigated.

ISSN:0021-8979    

DOI:10.1063/1.328034

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Piezoresistive properties of thick‐film resistors obtained with ink series supplied by different manufacturers have been investigated as a function of composition, structure, sheet resistivity, and applied strain between 0 and ±1000 &mgr; strain. The strain sensitivity of thick‐film resistors appears to be a strong function of the nature of the conductive grains and of the sheet resistivity of the paste; the results obtained suggest a dominant role of the tunneling effect in the conduction mechanism and in the strain sensitivity.

ISSN:0021-8979    

DOI:10.1063/1.328035

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We discuss bias‐induced threshold switching in chalcogenide‐glass thin films, with an emphasis on the unique aspects of this phenomenon. The electronic nature of both the ON state and the recovery process is now clear. In this paper, we also establish the fundamentally electronic origin of the initiation process. An isothermal model is presented and analyzed for filamentary ON‐state solutions via a set of phenomenological kinetic equations consistent with recent advances in our understanding of the electronic structure of chalcogenide glasses. The predictions of this model compare favorably with a variety of experimental results. The model is basically that the switching transition develops when a critical electric field is reached somewhere in the sample, usually near an electrode. Field‐induced carrier generation then causes the charged traps in the bulk to fill (neutralize). When all the traps are filled, carriers can transit the sample with an enhanced mobility and the generation rate required to keep the traps filled is reduced from its threshold value.

ISSN:0021-8979    

DOI:10.1063/1.328036

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The electrical characteristics of Au/n‐TiO2Schottky diodes have been studied usingI‐VandC‐Vmeasurements. TiO2samples with working face perpendicular to thecaxis are reduced in a vacuum of 10−6Torr at 800 °C for about 5 h and then quenched. The resistivities are in the range 20–30 &OHgr; cm. The barrier heights deduced fromI‐Vcharacteristics in agreement with the thermionic emission theory are in the range 0.87–0.94 eV.C‐Vdata yield lower barrier heights and show a frequency dependence attributed to relaxation phenomena occurring in a disturbed layer near the surface. Comparison with results relative to Au/n‐SrTiO3diodes shows that the barrier heights obey the Schottky model for these ionic semiconductors, confirming the role of the electron affinity in the band bending formation.

ISSN:0021-8979    

DOI:10.1063/1.328037

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The dynamics of a superconducting circuit of a loop broken by a Josephson junction shunted by a resistive loop is analyzed. Anomalous flux flow behavior predicted by the calculation is discussed.

ISSN:0021-8979    

DOI:10.1063/1.328038

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Resistive critical current densities, critical fields, and normal‐state electrical resistivities were obtained at 4.2 °K for 55 alloys in the Nb‐Ti‐Zr ternary alloy system, excepting Ti‐Zr binary compositions. The resistive critical field as a function of ternary composition has a saddle point between the Nb‐Ti and Nb‐Zr binaries, so that ternary alloying in this system is not expected to result in higher critical fields than the binary alloys.

ISSN:0021-8979    

DOI:10.1063/1.328039

出版商:AIP    

年代:1980

数据来源: AIP