摘要:

Trap centers in amorphous silicon nitride (a‐SiNx) have been considered to be amphoteric. We found two signals of Si33/4 Si0and N33/4 Si0(Si dangling bonds with an unpaired electron) by an electron‐spin‐resonance method, and estimated the hole trap density to be larger than the electron trap density by about one decade, using the nonvolatile memory devices. As a result, we propose a new portrayal in which electron/hole traps are at the interface between Si clusters anda‐SiNxbulk, and hole traps are at nitrogen vacancies ina‐SiNxbulk.

ISSN:0021-8979    

DOI:10.1063/1.346524

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper gives a thorough treatment of a new effect of non‐steady‐state photo‐electromotive‐force (emf). The effect consists of an alternating electric current arising in a short‐circuited bulk sample of a photoconductor illuminated by a vibrating sinusoidal pattern. As a detailed theoretical analysis shows, the frequency transfer function of the effect is identical with that of a differentiating RC circuit having a time constant equal to the characteristic time of a space‐charge grating formation within the sample volume &tgr;sc. For high excitation frequencies (&ohgr;≳&tgr;−1sc), the photo‐emf signal peaks at spatial frequencyK=L−1D(LDis the mean diffusion length of photoinduced carriers) and the photovoltage amplitude in an open‐circuit sample can be as high askBT/etimes the number of fringes of the interference pattern in the interelectrode spacing. The basic conclusions of the theoretical analysis of the effect are supported by the experimental evidence obtained for cubic photoconducting Bi12SiO20crystals.

ISSN:0021-8979    

DOI:10.1063/1.346525

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Because of its high diffusivity in silicon, aluminum is best suited for deep diffusions often required in high‐voltage‐power semiconductor devices. The ion implantation technique allows the reproducible low dosage doping necessary, e.g., for the new concepts of junction termination systems. The most important drawback of using aluminum as ap‐type dopant in silicon is its low electrical activity after the anneal. In order to obtain a deeper insight into the mechanisms responsible for the loss of the electrical activity, we have studied the states of aluminum implanted into silicon before and after annealing by means of spreading resistance, secondary‐ion mass spectroscopy, transmission electron microscopy, and energy‐dispersive x‐ray techniques. The case study presented here [Czochralski grown (100) silicon, implanted dose 3×1015cm−2, junction depth 6 &mgr;m] reveals that the major source for the loss of the electrical activity is out‐diffusion, i.e., segregation into the native silicon oxide layer and/or evaporation into the vacuum. In addition, the activity is reduced by the formation of aluminum oxide precipitates. The results are discussed in the light of optical studies on the same materials performed previously as well as on the basis of a diffusion model which allows for out‐diffusion. The large rate constant for out‐diffusion indicates that the native oxide layer represents a highly reactive surface for aluminum. From the diffusion model it is possible to calculate an approximate electrical activityA˜(xj) as a function of junction depthxj, which qualitatively reproduces well the observed activityA(xj). This demonstrates that our case study is representative for a large number of samples which were implanted and annealed under widely different conditions. Some technical processes which could possibly enhance the electrical activity are discussed.

ISSN:0021-8979    

DOI:10.1063/1.346526

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Data describing the deterioration of AlxGa1−xAs‐GaAs heterostructures in long‐term exposure (2–12 years) to normal room environmental conditions (∼20–25 °C, varying humidity) are presented. Optical microscopy, scanning electron microscopy, transmission electron microscopy, and electron dispersion x‐ray spectroscopy are used to examine AlxGa1−xAs‐GaAs quantum‐well heterostructure material that has hydrolyzed at cleaved edges, cracks, and fissures, and at pinholes in cap layers. The hydrolysis is found to be significant for thicker (>0.1 &mgr;m) AlxGa1−xAs layers of higher composition (x>0.85).

ISSN:0021-8979    

DOI:10.1063/1.346527

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The Schottky barrier height ofinsituepitaxial aluminum on AlxGa1−xAs was measured as a function of aluminum mole fraction fromx=0 tox=1, usingI/V,C/Vand activation energy plots of current‐voltage dependence on temperature. The excellent electrical properties of the molecular beam epitaxy grown AlGaAs layers, with residual deep levels concentrations of less than 1014cm−3combined with theinsitudeposition of single‐crystal epitaxial aluminum resulted in extremely high quality Schottky diodes fromx=0 (GaAs) tox=1 (AlAs) with accurately exponential current‐voltage characteristics over up to 10 decades and with ideality factors less than 1.03. Both theC−2−Vand activation energy plots were linear and yielded barrier heights in very good agreement with theI/Vones. The near‐ideal characteristics of these diodes were compared with several models of Schottky barrier formation and the dependence of the Schottky barrier height on the aluminum mole fraction was found to agree with the anion vacancy model within 10–20 meV, with a maximum deviation of 46 meV.

ISSN:0021-8979    

DOI:10.1063/1.346528

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Techniques have been developed to produce ohmic contacts to naturally occurring boron doped semiconducting diamond. Thin films of Mo, Mo/Au, and Mo/Ni/Au deposited on diamond produced adherent ohmic contacts after annealing at 950 °C. A thermally activated solid state reaction which produces a refractory carbide precipitate at the original diamond/metal interface is the principal factor in affecting the properties of the contacts. The interface reaction has been characterized using Auger electron spectroscopy, scanning electron microscopy, x‐ray diffraction, metallography, andI‐Vmeasurements.

ISSN:0021-8979    

DOI:10.1063/1.346529

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The kinetics of light induced defect generation or the Staebler–Wronski effect have been investigated on device quality hydrogenated amorphous silicon films which were deposited by dc magnetron reactive sputtering. The total hydrogen content (CH) of the films, which varied from ∼10 to 28 at. %, had a strong influence on the defect generation. LowCH(10%–15%) films had a high initial density of defect states (∼7 to 10×1015cm−3) compared to the highCH(≥17 at. %) films with a density of ∼3×1015cm−3. However, light exposure increased the defect density more slowly on the lowCHfilms, such that after about 1 h of light exposure their defect density was lower. A high‐quality glow discharge produced film was also measured, and behaved similarly to the highCHsputtered films. The greater stability of the lowCHfilms was also reflected in a slower decrease of the electron photoconductivity relative to the other samples. For exposure times (t) up to 1000 h, the total density of defect states of the films increases as a power law: the highCHand glow discharge deposited films followt0.3andt0.32, respectively, whereas the lowCHfilm showst0.23at long times. The latter behavior is in sharp contrast with previous reports, and indicates that the degradation does not follow the Stutzmann theory or obeys it with a 100× smaller susceptibility to degradation.

ISSN:0021-8979    

DOI:10.1063/1.346530

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Ion implantation through metal (ITM) or metal silicide (ITS) appears to be an attractive technique for self‐aligned silicided shallow junction formation. Since most of the implanted ions are confined in the barrier film, the damage generated in the silicon substrate is reduced and so is the required post‐implant annealing temperature. The purpose of this work is to study the capability of using Pt and PtSi in the ITM/ITS technique. As+ions were implanted through 30‐nm Pt or 60‐nm PtSi at 80 keV with doses ranging from 1×1015to 1×1016cm−2. The implanted samples were annealed from 650 to 800 °C. Junction depths measured by spreading resistance and secondary‐ion mass spectroscopy on 750 °C annealed samples are about 0.11 and 0.13 &mgr;m for the ITS and ITM schemes, respectively. The reverse area and peripheral leakage current density (JRAandJRP) are separated by measuring diodes of different size. All samples with a dose of 1×1015cm−2failed due to an insufficient amount of dopants which were incorporated into Si.For a dosage greater than 5×1015cm−2, theJRAat −5 V is less than 0.2 nA/cm2and the forward ideality factor is lower than 1.02 for the ITS samples annealed at 750 °C. Activation energy measurement shows that theJRAis diffusion‐component dominated while theJRPis generation‐component dominated at room temperature. Surface generation current and lateral implantation damage‐induced current are examined and discussed in detail. A possible reason is that the lateral junction depth is less than the vertical junction depth and the depletion region may be extended to near the PtSi/Si interface. Annealing at 800 °C degrades the junction characteristics because the Pt from PtSi diffuses into the junction region. Based on the experimental results and analysis we conclude that either Pt or PtSi film can be employed as an efficient barrier film in the ITM/ITS technique. A high‐quality and ultrashallow junction can be fabricated using furnace annealing at temperature as low as 750 °C. The peripheral current generated at the silicide/silicon interface dominates the reverse junction current and cannot be avoided for the silicided junction with a junction depth less than 50 nm from the interface. This factor acts as a physical limitation as the junction depth scales down.

ISSN:0021-8979    

DOI:10.1063/1.346531

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An investigation is made of the third stage in the series of solid‐state reactions that occur between InP and its most commonly used contact material, Au. This reaction, which results in the transformation of the contacting metallization from the pink‐colored Au3In to the silver‐colored Au9In4, is shown to be controlled by an In‐Au exchange or kickout mechanism operating at the interface between the two phases. Contact spreading, a rapid lateral expansion of the contact metallization that can consume large quantities of InP during growth, is shown to be another manifestation of this final stage in the InP‐Au reaction. A detailed description of the mechanisms, including an investigation of the kinetics of the processes involved, is presented.

ISSN:0021-8979    

DOI:10.1063/1.346532

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A study of grain alignment and its effect on the dc transport critical current in fine‐grained bulk Y1Ba2Cu3O7−&dgr;is reported in magnetic fields from 10−4T to 26 T. Two features distinguish the critical current densityJcof aligned bulk Y1Ba2Cu3O7−&dgr;from unaligned material. First, the effective critical field where the intergranularJcapproaches zero is about four times higher (30 T) for aligned samples with field parallel to thea,bplanes, than it is for polycrystalline unaligned samples (7 T). Second, the nearly field independent plateau value ofJcbetween 10 mT and 1 T is one to two orders of magnitude higher than typical plateau values ofJcin unaligned bulk‐sintered Y1Ba2Cu3O7−&dgr;, for field parallel to thea,bplanes. A low‐field (<10 mT) weak‐link decrease inJcwith magnetic field is still observed, but it is much smaller than for unaligned material. These data clearly demonstrate that alignment alone significantly reduces theweak‐linkproblem in fine‐grained polycrystalline samples with low‐aspect‐ratio (4:1) grains (unlike melt‐grown samples where there has been some ambiguity as to the relative importance of alignment versus large grain growth). Furthermore, the results provide strong evidence that there are two parallel components ofintergranularcurrent conduction, one consisting of weak‐linked material, the other behaving like intrinsic intragranular material that is not weak‐linked. A comparison with unaligned Y1Ba2Cu3O7−&dgr;indicates that the volume fraction of such nonweak‐linked material is significantly enhanced by grain alignment, but still only 0.01%–0.1% of the grain boundary area. Field‐cooled and force‐freeJcdata are also presented, along with detailed measurements of the shapes of the voltage‐current characteristics.

ISSN:0021-8979    

DOI:10.1063/1.346533

出版商:AIP    

年代:1990

数据来源: AIP