摘要:

Using the warm electron coefficient, the electron mobility, &mgr;inel, limited only by inelastic scattering was studied for two‐dimensional electron gas confined to the GaAs side of an N‐AlGaAs/GaAs heterojunction. The warm electron coefficient &bgr; was measured to be 0.1–3×10−3cm2/V2at the temperature 4.2–30 K. The electron mobility &mgr;inelis interpreted as the upper limit obtained in the condition free of ionized impurity scattering. The relation between &bgr; and electron mobility &mgr;inelfor two‐dimensional electron gas is obtained as &bgr;∝&mgr;inel, when ionized impurity scattering is predominant. Combining the theoretical relations and experimental results, the electron mobility limit of a two‐dimensional electron gas at 4.2 K is found to be about 9.0×106cm2/V sec at sheet electron concentration of 8×1010cm−2. The exponent of its temperature dependence is −1.28.

ISSN:0021-8979    

DOI:10.1063/1.334855

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Charge trapping in the insulator of a metal‐oxide‐semiconductor (MOS) structure strongly influences photocurrents resulting from electron photoinjection from the gate, or from the semiconductor electrode, into this insulator. This influence may be used to determine trapped charge distributions (profiles) in the dielectric layers of MOS structures. In this paper, several trapped charge profiles are considered, and the influence of these charges on the MOS structure photoelectric characteristics is discussed. Detailed solutions are derived for uniform, step, delta, rectangular, exponential, and Gaussian distributions of electrons trapped in the dielectric of a MOS structure. All these solutions are based on the barrier position mode approximation of the Powell–Berglund formulas. A comparison of experimentally obtained photocurrent‐voltage characteristics of a MOS structure (taken both before and after the charge trapping took place) with characteristics calculated using expressions derived in this paper allows approximate determination of the trapped charge profile in this particular sample.

ISSN:0021-8979    

DOI:10.1063/1.334856

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The dark conductivity and photoconductivity of pristine poly(p‐phenylene sulfide) (PPS) were investigated under strictly controlled experimental conditions. Apparent dark conductivity of pristine PPS increased by more than a decade after the sample was irradiated with UV light. The appearance of apparent high conductivity was found to originate from thermally released electronic carriers which had been captured in deep trapping sites. Dark conductivity of PPS measured in air was about 4 decades higher than that measured under high vacuum. Oxygen absorbed in PPS samples was found to behave as weak electron acceptors and to assist the production of electronic carriers. Large photoconductivity under steady‐state photoirradiation was found.

ISSN:0021-8979    

DOI:10.1063/1.334857

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A macroscopic model of the microcontacts in ceramic ZnO varistors was prepared by using ZnO single‐crystal plates and a layer of the usual oxide additives. The electrical properties of these model contacts are very similar to those of the microcontacts. Measurements on one‐sided macrocontacts require the assumption of a ‘‘buried’’ potential barrier underneath the surface of the ZnO, the formation of which is explained by the distribution of the atomic defects and the dopants in the ZnO. Based on this idea, theI‐Vcharacteristics in the prebreakdown region and the breakdown voltage have been calculated.

ISSN:0021-8979    

DOI:10.1063/1.334858

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this paper an analytic analysis of the breakdown voltage of an ion‐implanted junction is presented. A joined half‐Gaussian distribution of the implanted ions is used, since it gives better description of the impurity profiles. The results are based on a closed‐form solution of Poisson’s equation in the depletion region. Fulop’s average ionization coefficient is used to determine the values for the avalanche breakdown voltage as a function of implantation energy, implant dose, and substrate dopant concentration. The maximum electric field at junction breakdown is also calculated and the results are presented. Finally, the applicability and restrictions of the analysis are discussed.

ISSN:0021-8979    

DOI:10.1063/1.334859

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The hole‐electron pair generation region in a semiconductor bombarded by a scanning electron beam can be modeled as a circular cylinder tangent to the semiconductor surface. A cross‐sectional plane normal to the cylinder is then examined. Under conditions of high semiconductor surface recombination velocity, a conformal transformation of this plane can be made to yield a geometry in which the method of images can be used to match boundary conditions at the junction and at the semiconductor surface. Thus, a solution for the electron‐beam‐induced current (EBIC) problem can be found in this manner when the generation region is external to the diffused or implanted region of a finite junction depth. An infinite series of images can be used to solve the problem when the generation region is within the diffused or implanted region under conditions of low, as well as high, surface recombination velocity. Thus, expected EBIC results are presented as a function of junction depth.

ISSN:0021-8979    

DOI:10.1063/1.334860

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The domain wall velocity of ion‐implanted garnet films is measured on expanding stripe domains observed—using a laser‐flash optical microscope, for wide drive field and temperature range. Comparison of measured and calculated velocities shows the insufficiency of present theories. A simple model is suggested for describing the saturation velocity phenomena in implanted garnet films. This model shows the wall structure distortion at the effective films surfaces to be approximated by a transient Bloch line zone. The average static azimuthal angle is assumed to be &psgr;¯0=&pgr;2&Lgr;0/Din good agreement with the experimentally obtained &psgr;¯0=11.8 &Lgr;0/D, whereDis the effective film thickness and &Lgr;0is the Bloch line width parameter. The calculated saturation velocities agree surprisingly well with the experimental results for wide thickness and temperature range.

ISSN:0021-8979    

DOI:10.1063/1.334861

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Magnetic measurements of hysteresis loops and transverse susceptibilities have been done on as‐cast iron based amorphous alloys on the surface and in the bulk of the ribbons. Bitter technique has been used to obtain the domain patterns.a‐Fe78B13Si9shows an anisotropy perpendicular to the ribbon plane with maze domain ‘‘island’’ structures. The surface measurements do not detect any difference in behavior compared to the observed bulk properties.a‐Fe81.5B14.5Si4shows different behavior in the surface and in the bulk of the ribbon with a perminvar‐type hysteresis loop from the surface and magnetization perpendicular to the ribbon plane with well‐aligned closure domains. The analysis of the different magnetic experimental data and selective changes in the internal stresses produced by different treatments support a model of the layered character of the anisotropies in this sample with tensile stresses and in‐plane anisotropy in the surface and compressive stresses and anisotropy perpendicular to the ribbon’s surface in the bulk. Finally, a rough calculation shows that the thickness of the surface in‐plane anisotropy region is of the order of the surface roughness.

ISSN:0021-8979    

DOI:10.1063/1.334862

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The magnetic properties of micrometer‐size Permalloy thin films have been investigated for a variety of sample thicknesses, aspect ratios, and sizes. The formation of edge domains was an important factor in the magnetization response of the sample to an applied external magnetic field. Sample coercivity depended on the length of the domain wall structure. Small specimens (6.5 &mgr;m wide) have high coercivity, whereas large samples (104 &mgr;m wide) approach the bulk‐film value. The reduced length, defined as the ratio of the edge‐domain extent (or characteristic length) to the sample length, and its dependence on sample size, aspect ratio, and thickness were studied. Samples with low aspect ratio have wall structures throughout the specimen, giving rise to higher coercivities and correspondingly larger reduced lengths. Samples with large aspect ratio have wall structures confined to the edge areas, lower coercivities, and shorter reduced lengths. The absolute domain size increased as the sample increased, and reduced length approached a constant value for all samples with a given aspect ratio. The reduced length was approximately proportional to the reciprocal of the aspect ratio.

ISSN:0021-8979    

DOI:10.1063/1.334863

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Optical detection of magnetic resonance applied to theFcenter in KCl is presented. The advantages and the theoretical basis of the technique of optical detection of magnetic resonance are discussed, and a description of the details of the actual spectrometer designed for the study of color centers is given. The successful observation of the optical detection of the resonance of the KClFcenter is reported.

ISSN:0021-8979    

DOI:10.1063/1.334864

出版商:AIP    

年代:1985

数据来源: AIP