摘要:

A transient photocurrent measurement with a zero-field time-of-flight configuration was carried out on ITO/ZnO/CdS(n-type)/Cu(In,Ga)Se2(p-type,Eg=1.15 eV)/Mo/glass solar cell to get the information about the minority carrier transport on theCu(In,Ga)Se2film. The transient photocurrent was recorded after the incidence of a subnanosecond pulse light (500 nm wavelength) from the back side through the Mo thin film (<0.5 &mgr;m). The analysis of the transient photocurrent was conducted by using the time-dependent diffusion current equation. Consequently, the values of1.0 cm2/s,100 ns, and103 cm/sas the diffusion coefficient, the minority carrier lifetime, and the recombination velocity in theCu(In,Ga)Se2/Mointerface, respectively, were obtained on theCu(In,Ga)Se2film. These data corresponded to the electron beam induced current line profile data, and the experimental data ofJ0,analyzed by current–voltage characteristics. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365675

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Double pulse doped AlGaAs/InGaAs/AlGaAs pseudomorphic high electron mobility transistor (PHEMT) structures have been grown onInxGa1−xAs(x=0.025–0.07)substrates using molecular beam epitaxy. A strain compensated, AlGaInAs/GaAs superlattice was used for improved resistivity and breakdown. Excellent electrical and optical properties were obtained for 110-Å-thick InGaAs channel layers with indium concentrations up to 31&percent;. A room temperature mobility of6860 cm2/V swith 77 K sheet density of4.0×1012 cm−2was achieved. The InGaAs channel photoluminescence intensity was equivalent to an analogous structure on a GaAs substrate. To reduce strain PHEMT structures with a composite InGaP/AlGaAs Schottky layer were also grown. The structures also exhibited excellent electrical and optical properties. Transmission electron micrographs showed planar channel interfaces for highly strainedIn0.30Ga0.70Aschannel layers. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365676

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A Gummel–Poon model for abrupt, single heterojunction Npn bipolar phototransistors is described including the effects of the dc base bias on the current and optical gains. Initially, the excess electron concentration at the emitter end of the quasineutral base is determined by matching the thermionic field emission across the emitter–base heterojunction with the diffusion current at the emitter end of the base and including the effects of optical generation. The result is used in determining the electron profile in the base from which the base charge and the electron component to the emitter and collector currents are calculated following the Gummel–Poon model. The photocurrent’s components due to optical absorption in the quasineutral base, the base–collector space charge region, and the collector region are determined taking into account the nonuniform optical generation assuming topside illumination. A comprehensive description of the recombination current components is incorporated including the effects of optical absorption on recombination. The model is then used to calculate the dc and small signal current gain and the device’s optical gain, and to examine the effects of dc biasing and the optical power level. The simulation results are compared with the available experimental results and reasonable agreement is found. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365677

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The magnetization-curling mode in a columnar-structure film with perpendicular magnetization is studied on the assumption that the film is a two-dimensional array of cylinders. The angular dependence of the nucleation fieldHNis calculated by the Ritz method and compared with that for the coherent-rotation mode. It is found that the magnetization rotates in the curling mode for a large reduced radiusSand in the coherent-rotation mode for a smallS.The angular dependence ofHNis different from that in an infinite cylinder. IfSis large, the magnetization rotates in the curling mode for any value of&thgr;0,where&thgr;0is the angle between the applied field and the cylinder axis. WhenSis medium, the magnetization rotates in the coherent-rotation mode for a small&thgr;0and in the curling mode for a large&thgr;0.©1997 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.365678

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Double relaxation oscillation superconducting quantum interference devices (DROSs) with a gradiometric signal SQUID and either a reference SQUID or a reference junction will be presented in this article. The devices are user friendly, particularly those with a reference junction. Because of the large flux-to-voltage transfer of∂V/∂&Fgr;=0.7–1 mV/&Fgr;0,the devices can be operated in a flux locked loop based on direct voltage readout without loss of sensitivity. The typical white flux noise of the DROSs amounts to&sqrt;S&Fgr;=5–6&mgr;&Fgr;0/&sqrt;Hz,which corresponds to an energy resolution&egr;=S&Fgr;/2Lsq≃200 h.Coupled to an external planar first-order gradiometer, a white magnetic field sensitivity of&sqrt;SB<2 fT/&sqrt;Hzwas measured inside a magnetically shielded room. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365679

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We analyze Fiske resonances of one-dimensional parallel arrays of underdamped Josephson tunnel junctions. They appear in the current voltage(I–V)characteristics as resonant current singularities (steps) at finite voltagesVmwhen a magnetic fieldHis applied perpendicular to the array cells. We present measurements of current step amplitudesIcm,and of the maximum Josephson currentIc0as a function ofH,for arrays made of four, six, and ten small Josephson junctions. TheI–Vcharacteristics of the arrays exhibit three, five, and eight resonant current steps, respectively, at increasing voltages. In all devices we find that the current amplitude of the highest order step has just one maximum occurring atH≈1/2H*,beingH*the first field value whereIc0(H*)≈Ic0(0).Numerical simulations of the phase dynamics in small parallel arrays as a function of the applied magnetic flux are performed. The results of the simulation reproduce the experimentally observed features. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366288

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

UsingB-dot probes Meyer &etal; [J. Appl. Phys.79, 1298 (1996)] have described a method for calculating the azimuthal current, electric field, plasma permittivity, and electron density in a planar inductively coupled plasma source. They assume the phases associated with the time rate of change of the radial and axial field components to be the same. Furthermore, they restrict their analysis to the situation where the phase is independent of radius. We demonstrate that the phases for the two field directions are different. The subsequent modified forms for the plasma properties considered by Meyer &etal; are presented. We also show that their procedure can be extended to cover phases which are an arbitrary function of position, and for completeness, give forms for the generalized plasma properties. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365680

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

InCH4–H2mixture dc discharges, theCH2radicals are identified from hot H atom laser-induced fluorescence Doppler spectral profiles. We examine the possible contributions of hydrocarbon species present in the discharge, which could be dissociated by the laser photons and produce the fast H atom fragments responsible for these profiles. The dissociation energy, 4.2±0.2 eV, experimentally determined indicates that we detect mainlyCH2radicals. At a pressure of 2 Torr and a discharge current intensity of 10 mA, we show that theCH2radical density increases almost linearly with the percentage—until 15&percent;—ofCH4in the gas mixture, while the population density of the H atoms created in the plasma remains quasiconstant, except in the cathode sheath. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365681

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The sensitivity of acoustic techniques to topological and/or morphological variations in SiC/porous SiC laminated ceramics is studied within the transfer matrix formalism. To implement this theoretical formalism, the mechanical properties of the SiC porous layers are calculated using the effective medium approximation of Kuster and Tokso¨z [Geophys.39, 587 (1974)]. We show that topological defects have a stronger acoustic signature than morphological defects. Also, we observe that there are particular frequencies at which the defects do not present any acoustic signature. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365682

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Pulsed KrF laser annealing can suppress the island structure formation and Ge segregation associated with the interfacial reactions ofNi/Si0.76Ge0.24.For theNi/Si0.76Ge0.24films annealed at an energy density of0.1–0.3 J/cm2nickel germanosilicide associated with the amorphous overlayer was formed, while at energy densities above0.4 J/cm2cellular structures of Ge-deficientSi1−xGexislands surrounded byNi(Si1−xGex)2due to the constitutional supercooling occurred. For the continuousNi(Si1−xGex)films grown at 200 °C, subsequent laser annealing at a higher energy density of0.6–1.0 J/cm2caused transformation into homogeneousNi(Si0.76Ge0.24)2films without island structure and Ge deficiency which readily appeared on furnace annealing at temperatures above 400 °C. At energy densities above1.6 J/cm2the same cellular structures as described above were also noted. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365683

出版商:AIP    

年代:1997

数据来源: AIP