摘要:

Deep‐level transient spectroscopy has been carried out using Schottky diodes fabricated onn‐In0.53Ga0.47As grown by liquid phase epitaxy (LPE). A defect level corresponding to oxygen having an activation energyEc−0.32 eV and capture cross section 7×10−17cm2was observed. Depth profiling of shallow donors and oxygen showed that concentrations of both these impurities increased towards the surface of the epilayers. Dy gettering during LPE growth significantly reduced the oxygen concentration and also resulted in lower etch‐pit density. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359371

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The interfacial defects at thep‐Si epitaxial layer/p‐Si substrate interface have been studied by deep‐level transient spectroscopy (DLTS). By solving Poisson equation, the electron concentration at the defect level varied with external voltage is derived. The emission and capture of electrons at the defect level, which are not observable in conventional DLTS, can be detected simultaneously in a single temperature scan by properly choosing the experimental parameters. The experimental results show that the energy level of the interfacial defects is located atEc−0.30 eV. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359372

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A nonlinear parametric interaction is found in the magnetoplasma in a semiconductor. The spatial asymmetry is produced by the magnetic field in the Voigt configuration, where the Lorentz force acts on the drifting electrons. The nonpolar semiconductor can be used as the nonlinear optical element. The optical parametric conversion and the second‐harmonic generation are discussed. The device operates in the infrared range. The efficiencies are found to be much larger than in conventional nonlinear optical crystals. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359601

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In this paper, calculations of the hole initiated interband impact ionization rate in bulk silicon and GaAs are presented based on an ensemble Monte Carlo simulation with the inclusion of a wave‐vector‐dependent numerical transition rate formulation. The ionization transition rate is determined for each of the three valence bands, heavy, light, and split‐off, using Fermi’s golden rule with a two‐body, screened Coulomb interaction. The dielectric function used within the calculation is assumed to be wave‐vector‐dependent. Calculations of the field‐dependent impact ionization rate as well as the quantum yield are presented. It is found from both the quantum yield results and examination of the hole distribution function that the effective threshold energy for hole initiated impact ionization is relatively soft, similar to that predicted for the corresponding electron initiated ionization rate threshold in both GaAs and silicon. It is further found that light‐hole initiated ionization events occur more frequently than either heavy or split‐off initiated ionization events in bulk silicon over the applied electric field strengths examined here, 250–500 kV/cm. Conversely, in GaAs, the vast majority of hole initiated ionization events originate from holes within the split‐off band. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359374

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Both the optical absorption coefficient &agr;, and the carrier densityN, of semiconducting thin films are analytically investigated in relation with their deposition substrate influence. It is shown that these two properties are sensitive to the film thicknessd, particularly when incident monochromatic light is very close to the film transmission cutoff wavelength. &agr; behaves according to the &agr;≊f(d−1) type of function whileNobeys the lawN≊f(d−m) whose precise form varies withmvalue and depends on the substrate influence. Experimental results report on sprayed CdS films respectively deposited on glass, SnO2, and ITO substrates which illustrate the suitability of the model proposed. The film absorption coefficient is affected by the migration phenomenon at the film‐substrate interface, the rate of the migration depending upon the substrate involved.m≊1 obtained with SnO2andm≊2 with ITO indicate different CdS film interface properties, typical of the substrate used. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359382

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Results are presented of admittance spectroscopy measurements on the lattice‐matched In0.52Al0.48As/In0.53Ga0.47As single‐quantum‐well structures. It has been found that the perpendicular conductivity of the structure is controlled by the strong temperature dependence of the space‐charge region width around the quantum‐well layer. This process is governed by a high density of deep electron traps present in the layers adjacent to the quantum well. Therefore, the energy activation of perpendicular conductivity is determined by the deep‐level defects rather than the thermionic emission of electrons from the quantum well. Because of this, it is impossible to extract the magnitude of the band offset between the quantum well and barrier layers from the admittance measurements performed in this study. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359383

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A method for the determination of interface properties between a depleted heteroepitaxial layer and a substrate is presented. The method is based on the measurement of the zero bias capacitance of a metal gate that forms a Schottky contact with the depleted epilayer. The interface charge density can be extracted regardless of the exact values of the energy band discontinuities. A microscopic electrostatic analysis of the interface is presented which takes into account the effects of interface charges and interface dipoles. Experimental results are presented for the case of ZnTe epilayers grown by metal organic chemical vapor deposition on CdTe substrates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359384

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Thin‐film, composite mixtures of YBa2Cu3O7−&dgr;(YBCO) and Y2O3(yttria) have been grown by off‐axis sputtering onto (100) SrTiO3and (100) and (110) MgO. X‐ray‐diffraction measurements for films grown on (100) substrates show the presence ofc‐axis‐oriented YBCO and (h00)‐ordered yttria. The composites deposited on (110) MgO are insulating, and x‐ray analysis shows the presence of Y2Ba1Cu1O5along withc‐axis YBCO. Scanning electron microscopy analysis shows the films to be very granular. The superconducting transition temperature and resistivity ratios between 300 and 100 K of the composites grown on the (100) substrates have been measured. A dramatic change is seen in these transport properties around 70% (volume) of YBa2Cu3O7−&dgr;, which may be explained by the phase diagram for Y‐Ba‐Cu‐O. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359385

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The superconducting properties of binary and ternary niobium compounds for rf applications are investigated. The materials under study are niobium nitride (NbN), niobium‐titanium nitride (NbTiN), and niobium tin (Nb3Sn). Preparation techniques of the compounds are discussed. NbN and NbTiN are obtained by thermal reaction of bulk Nb in nitrogen atmosphere. Nb3Sn has been obtained using a technique originally developed for high‐field magnet fabrication and modified to be applied to rf cavity production. The experimental apparatus and measurement technique are described. In particular the raw experimental data have been carefully analyzed to obtain important informations on fundamental material parameters. The effect of field penetration in the superconductor and the influence on the experimental results of the normal metallic substrate on which the superconductor is grown is also considered. The measurements show that NbN and Nb3Sn are effectively potentially good materials for rf applications due to their low theoretical BCS surface resistance. So far the results obtained with NbTiN are more difficult to interpret because the quality of the material did not allow sufficiently accurate collection of data. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359386

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Overwrite repeatability of exchange‐coupled multilayer for light‐intensity‐modulated overwrite (OW) was studied by using Arrhenius analysis. A computer simulation showed that typical OW disks and a conventional nonoverwrite (NOW) disk have similar maximum temperature during recording. Nevertheless, the overwrite repeatability of the OW disks was smaller than that of the NOW disk. The degradation mode characteristic to the OW disks was found to have lower activation energy than the conventional NOW single‐layer disk. The degradation mode was caused by initialization noise resulting from domain‐wall fluctuations under a large initializing field, and was reduced by using a transition‐metal dominant memory layer with high‐domain‐wall coercivity. An overwrite repeatability of more than 106was achieved. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359602

出版商:AIP    

年代:1995

数据来源: AIP