摘要:

Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) measurements have been carried out on the &bgr;‐SiC(100) surface simultaneously. The AES and XPS results differ significantly in the bonding state of oxygen for both as‐grown surfaces and as‐etched surfaces. Differences in the same carbon‐KLLAuger spectra induced by both electron beams and x rays from the same surface suggest that the electron beam used in AES removed considerable amounts of carbonaceous species in the contaminant layers. Furthermore, comparison of the Si 2pand SiLVVspectra revealed that the SiOx(x<2) species on the surface was also reduced by the electron beam used in AES. Although previous AES results have shown that both as‐grown and as‐etched surfaces of &bgr;‐SiC(100) were covered with only submonolayer coverage of oxygen bonded to Si atoms, with no detectable carbonaceous contaminants, this work shows that the real surfaces, however, are covered with several tens of contaminant layers, including SiO, CC, CH, and CO bonds.

ISSN:0021-8979    

DOI:10.1063/1.345301

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The presence of electrically active defects in C+and CO+implanted boron‐doped silicon has been monitored using deep level transient spectroscopy and resistivity measurements. Activation energies of trapped carriers, implanted ion dependencies, and annealing behavior of these defects have been determined. The introduction of defects by annealing has been observed. A total of ten hole and electron traps are reported. Among these traps, a dominant hole trap 0.65 eV above the valence band, and an electron trap 0.53 eV below the conduction band, are tentatively ascribed to the silicon di‐interstitial and the carbon‐oxygen pair, respectively. Other traps detected in the samples have been correlated with multi‐oxygen‐ and carbon‐related complexes. Annealing at temperatures up to 400 °C gives rise to similar deep level transient spectroscopy spectra comprising the same traps in both C+and CO+implanted material. However , annealing at temperatures >500 °C produces defect states that are dependent on the implanted ion species.

ISSN:0021-8979    

DOI:10.1063/1.345247

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We characterize by electrical techniques uniformly Si‐doped AlAs layers and short‐period GaAs‐AlAs superlattices grown in the same conditions by molecular‐beam epitaxy. Deep level transient spectroscopy shows that both the layers and the superlattices contain theDXcenter. The AlAs layers contain, in addition, a distribution of electron traps emitting in the temperature range 50–200 K. Using electron irradiation to introduce defects as probes we verified that the band structures of the superlattices we deduce are consistent with theoretical calculations using a widely accepted value of the band offset (67%). Finally, we observe that theDXcenter remains present, with the same ionization energy, when the energy position of the first &Ggr; miniband varies while the firstLminiband remains practically at the energetical position of theLband in the AlAs barriers. From this result we conclude that theDXcenter is linked to theLband and thus must be ascribed to anLeffective‐mass state.

ISSN:0021-8979    

DOI:10.1063/1.345248

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Numerical expressions of the piezoelectric and deformation electric fields associated with dislocations in zinc‐blende semiconductors are presented. They are used to calculate the optical absorption which they induce. These results are compared with the previously calculated charged‐line field absorption. For GaAs, we find that the latter one is prevailing and that the deformation electric field can be always neglected. Application of this model to experimental results in GaAs lead us to propose a two dislocation energy band scheme. One dislocation energy band D1 is located above the valence band and the other D2 is near midgap.

ISSN:0021-8979    

DOI:10.1063/1.345249

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A quantitative comparison between theory and experiment is presented for the thermoelectric power ofn‐type Si at low temperatures, where crystal boundary scattering of phonons is predominant. The expression for the Seebeck coefficient is obtained by simultaneously solving the coupled Boltzmann equations for electrons and phonons. The thermoelectric power is measured from samples of two different donor concentrations (ND=8×1014cm−3and 7×1015cm−3) at temperatures ranging from 25 to 200 K, where the thickness is varied by etching the samples (370–73 &mgr;m). The phonon mean free path for crystal boundary scattering, determined from experimental thermopower, agrees well with that gained from the theory of thermal conductivity corrected for the phonon velocities of interest. An additional measurement of the thermal conductivity yields the mean free path for phonon–phonon scattering, which is about two orders of magnitude less than that obtained from thermopower. This difference confirms the influence of the different parts of the phonon spectrum involved in the calculation of the appropriate transport parameters.

ISSN:0021-8979    

DOI:10.1063/1.345250

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Time‐of‐flight and photoluminescence measurements are performed forp‐GaAs samples at room temperature to investigate minority electron transport properties under high electric field. Reduction of drift velocity, absence of negative differential resistance, and thermally nonequilibrium states between electrons and holes were observed. These features were different from those for majority electrons and indicate strong dependence on hole concentration. Through studies of the energy loss rate and energy and momentum relaxation times, and by performing Monte Carlo calculations including electron‐hole interaction, it is clarified that the energy and momentum transfers by electron‐hole interaction have significant effects on minority electron transport property.

ISSN:0021-8979    

DOI:10.1063/1.345251

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have investigated the thermal dependence of low‐frequency current oscillations in the range of 140–400 K for semi‐insulating (SI) GaAs resistor structures illuminated with sub‐band‐gap light. We have also investigated the spectral dependence of the low‐frequency current oscillations in SI GaAs for illumination in the range of 0.85–1.25 &mgr;m. We find that the oscillation frequency is proportional to the carrier concentration. The thermal and the spectral measurement results both support the hypothesis that the low‐frequency oscillations are caused by carriers interacting with the EL2 level and that the presence of holes can significantly alter the oscillation frequency. The behavior of the oscillations can be qualitatively described by a simple empirical expression with the assumption that EL2 exhibits field‐enhanced capture from the &Ggr; valley, although the exact behavior of the enhanced capture is not fully understood.

ISSN:0021-8979    

DOI:10.1063/1.345252

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of subsequent heat treatments on the electrical properties of ion‐implanted layers in GaAs have received little attention. This is of paramount importance as far as both the industrial applications and the understanding of the physics behind the incorporation of dopants in GaAs are concerned. In this work, we have observed reversible changes in the sheet carrier concentration of the rapid thermally annealed Se‐implanted GaAs samples during subsequent heat treatments. The carrier concentration is observed to reach a limit for a certain temperature at sufficiently long annealing times. By noting the initial rate of change of the carrier concentration during subsequent heat treatments, an activation energy in the range of 1.6–2.5 eV has been identified for these samples. It is concluded that the rate dependent process for such reversible reactions is the diffusion of gallium atoms/vacancies. The electrical profiles of the Se‐implanted samples have also been modified during the annealing processes.

ISSN:0021-8979    

DOI:10.1063/1.345253

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper presents the first attempt in correlating the low‐frequency noise with the surface characteristics of metal films prepared by sputtering of copper onto oxidized‐silicon and sapphire substrates. Results show that the noise behaviors and the surface physics of the metal films on these two kinds of substrates are different from each other. Particularly, the spectral slope of noise spectrum not only depends on the substrate but also on the thickness and surface area of the metal films. These observations suggest that the low‐frequency noise of metal film, being governed by the surface roughness and irregularity of the sample, should be a surface effect. In addition, a number fluctuation model based on the electron tunneling between the hillocks at the surface is proposed to explain the observations.

ISSN:0021-8979    

DOI:10.1063/1.345254

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We present the remnant polar Kerr rotation and ellipticity for a Co/Pd superlattice. The magneto‐optical properties of Co/Pd superlattice thin films have been investigated by measuring both the polar Kerr and ellipticity hysteresis loops at a wavelength of 780 nm. It was found that the remnant Kerr rotation was strongly dependent on the thickness of Co and Pd sublayers as well as the total film thickness. In this system, the maximum polar Kerr rotation of 0.43° was observed at the film thickness of 110 A˚, where each bilayer was composed of 2‐A˚‐thick Co and 9‐A˚‐thick Pd sublayers.

ISSN:0021-8979    

DOI:10.1063/1.345255

出版商:AIP    

年代:1990

数据来源: AIP