摘要:

We present results from both experimental and theoretical studies of single and double carrier injection into amorphous silicon alloys. For biases above approximately half the built‐in potential double carrier injection in forward biasedp‐i‐ndiodes leads to higher currents than are obtained for single carrier injection inn‐i‐ndiodes. Single carrier injection was found to depend mainly on the density and distribution of localized states in the gap, whereas double injection currents are also very dependent on the recombination kinetics and the carrier band mobilities. Analysis of experimental results suggests that for an electron band mobility of 20 cm2/V sec the hole band mobility is approximately 4 cm2/V sec.

ISSN:0021-8979    

DOI:10.1063/1.336067

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This paper first reviews the properties of silicon carbide, in which polytypism is a salient feature. If a highly compensated insulating polytype is sandwiched between low resistive polytypes, space‐charge injection will occur. The theory of space‐charge‐limited current flow in the presence of traps is reviewed and a somewhat different version of the standard theory is presented, which shows more clearly the ohmic and space‐charge‐limiting regimes. Close analytical parametric forms forIandVare obtained. Experimental data onI‐Vcharacteristics and impedance are presented for 52–300 K. Except at the highest temperature, four regimes are clearly visible in theI‐Vcurves. A quantitative comparison with the theory is made and various transport quantities for &agr;‐SiC are deduced.

ISSN:0021-8979    

DOI:10.1063/1.336042

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Noise spectra of &agr;‐SiC in the presence of space‐charge‐limited flow are attributed to trapping noise. In the ohmic regime,S&Dgr;I∝I20and in the ohmic and low‐voltage quadratic regimeS&Dgr;I∝I0‖V0‖ as required by the theory. The trapping levels are determined from the slope of the time constants versus 1/T; the results are in fair agreement with those obtained from the current‐voltage characteristic. The magnitude of the noise requires a modulation mechanism, such as caused by mobility fluctuations in the temperature range where ionized impurity scattering dominates.

ISSN:0021-8979    

DOI:10.1063/1.336043

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The dark current‐voltage characteristics ofp‐i‐nhydrogenated amorphous silicon diodes with various thicknesses of the intrinsic layer (i‐layer) (770–9300 A˚) are systematically investigated. The magnitude of the forward current is found to be independent of thickness of theilayer, which is obviously against the simple conventional junction theory. It has been demonstrated through various experiments that the forward current of amorphousp‐i‐ndiodes is limited by a layer thinner than 770 A˚, possibly being thep/iinterface or a narrow zone of theilayer.

ISSN:0021-8979    

DOI:10.1063/1.336044

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The properties of tunnel barriers made with amorphous Ge (a‐Ge) deposited at approximately 80 K were studied in Al/a‐Ge/Al tunnel junctions and also in junctions where one electrode was Ni or Fe. The conduction process was shown to be tunneling for barriers less than about 100 A at liquid He temperature and consistent with Mott variable‐range hopping for higher temperatures and thicknesses. Measurements were made of current densityJand dynamic conductancedJ/dVas a function of voltageV, thicknesss, and temperatureT. The measurements were compared with available theoretical expressions for rectangular tunnel barriers based on the WKB approximation. The applicability of these expressions for barrier heights less than 100 meV was examined and a modified equation forJ(V) was derived which eliminated assumptions which are inaccurate for such low barriers. The measurements were also compared to this modified equation and to numerical solutions. Values for the effective tunnel barrier height ranging from 20 to 80 meV were obtained. Theoretical expressions forJ(V) could be fitted to the measurements fairly well, but not perfectly; forJ(T) the fit was poor. Values ofsobtained using the modified expression forJ(V) tended to be 10%–20% less than those measured by a quartz‐crystal thickness gauge using the bulk crystal density. The conductance peaks corresponding to the peaks in the superconducting density of states were considerably broadened over Al/Al2O3/Al junctions either because of depairing of the Al films in contact witha‐Ge or from an inelastic process in the barrier. No spin polarization of the tunnel currents was observed when one of the electrodes was Ni or Fe. Some measurements were made ofa‐Ge barriers treated with glow discharges in N2, O2, and H2. The properties ofa‐Ge were very similar to those previously found fora‐Si. Evidently the basic conduction process in these junctions is tunneling, but the simple tunneling model cannot entirely explain the results. Various proposals to account for these divergences from the simple tunneling model are discussed.

ISSN:0021-8979    

DOI:10.1063/1.336045

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Interface potential barrier heights for ultrathin silicon oxides (15– 44 A˚) on silicon and effective electron masses in some of these oxides are evaluated. Evaluation is performed using a new technique of analyzing the charging characteristics of metal‐nitride‐oxide‐semiconductor capacitors. Oxides thicker than 36 A˚ have the same potential barrier heights as those for thick oxides, assuming the effective electron mass of the oxides is the same. However, for oxides thinner than 31 A˚, the potential barrier heights decrease and the effective electron masses increase as the oxide thickness decreases. These results suggest that oxides at least thicker than 36 A˚ can be applied to metal‐oxide‐semiconductor field‐effect transistors as gate oxides.

ISSN:0021-8979    

DOI:10.1063/1.336046

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The barrier heights of Er and ErSi2on oxide‐freep‐Si have been reported to be identical (&fgr;pB∼0.8 eV), suggesting that the stoichiometry of the metallic contact does not appear to affect the barrier heights as long as a specific metal is present at the interface. In this work, the effects of Ge in the Er film on the barrier height have been investigated. Our results show that the ratio of Ge to Er in an Er/(GexSi1−x)2compound layer in contact withp‐Si affects the barrier heights significantly. A linear relationship between &fgr;pBandxhas been found and can be expressed as &fgr;pB=0.778 −(2x) (0.098). This experimental finding indicates that the barrier height of a metallic compound on Si may depend not only on the metal species, but also on the composition of the compound.

ISSN:0021-8979    

DOI:10.1063/1.336047

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A line‐sampling multiframe stroboscopic observation system was attached to a commercial‐type 200‐kV scanning electron microscope for dynamic observation of ferromagnetic domains in grain‐oriented 3% silicon steels with orientation near (110) [001]. This technique has enabled the individual stroboscopic image, at different phases of drive field, to be observed on a display tube simultaneously, leading to a more comprehensive understanding of core‐loss characteristics of the silicon steels magnetized at commercial frequency in practical use. The observation has clearly revealed that uniform displacement of domain walls according to the alternating magnetization at commercial frequency leads to lower core losses during operation.

ISSN:0021-8979    

DOI:10.1063/1.336048

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This paper gives formulas for analyzing the curling state. Magnetostatic energy of magnetic thin films having volume and surface charges can be calculated from the formulas, expressed in terms of film thicknessT, film widthW, saturation magnetizationM, length of curling regionD, and angle &thgr;0between the magnetic moment and the film edge surface. Using the formulas, we have quantified the magnetization distribution in the film edge layer and the decrease in energy caused by conversion from surface charges into volume charges.

ISSN:0021-8979    

DOI:10.1063/1.336049

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Coherent multilayers of interheavy rare‐earth metals have been synthesized by sputtering. The antiferromagnetic‐ferromagnetic transition temperature is suppressed with decreasing modulation wavelength in the TmnLumsystem.

ISSN:0021-8979    

DOI:10.1063/1.336050

出版商:AIP    

年代:1985

数据来源: AIP