Electrical properties of β‐FeSi2/Si heterojunctions
15 Nov 1991-Journal of Applied Physics (American Institute of Physics)-Vol. 70, Iss: 10, pp 5423-5426
TL;DR: In this paper, the electrical properties of polycrystalline films of β-FeSi2 grown on n-type single-crystal silicon are investigated, showing that multistep tunneling is the current conduction mechanism due to a high density of interface defects.
Abstract: The electrical properties of heterojunctions of polycrystalline films of β‐FeSi2 grown on n‐type single‐crystal silicon are investigated. The dark current‐voltage and capacitance‐voltage characteristics are measured over a wide temperature range. Analysis of the data reveal that multistep tunneling is the current conduction mechanism due to a high density of interface defects.
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TL;DR: The magnetic field dependence of the Hall coefficient in n-type β-FeSi2 was observed in the temperature range of 30-300 K and explained in the limits of a two-band model as discussed by the authors.
Abstract: The results of the transport and magnetization measurements on β‐FeSi2 single crystals are presented. The magnetic field dependence of the Hall coefficient in n‐type β‐FeSi2 was observed in the temperature range of 30–300 K and explained in the limits of a two‐band model. The magnetization measurements were performed within the range 4.2–300 K. It was shown that the contribution of the anomalous Hall effect to the total Hall voltage is negligible. Parameters of charge carriers, taking part in conductivity were calculated and the separation between the bands was estimated.
54 citations
TL;DR: In this article, the p-type conductivity of undoped single crystals reported in literature results from non-intentional doping by the high impurity level of the source material used, indicating that the single crystal properties were significantly influenced by intrinsic defects caused by deviations from the strictly stoichiometric composition and not by extrinsic factors.
Abstract: High-purity single crystals are necessary to investigate the intrinsic properties of undoped β-FeSi2 in dependence on the deviation from the stoichiometric composition. Therefore, iron was prepared with high purity with respect to metallic as well as non-metallic impurities and used as initial material for growing β-FeSi2 single crystals by chemical vapour transport in a closed system. By the optimization of the whole preparation process a single crystal purity of about 99.996% by weight could be achieved. The content of the main electrically active elements was lowered to about 20 wt ppm. Starting from a certain purity only n-type single crystals were obtained in equilibrium with FeSi as well as with Si. It is concluded that the p-type conductivity of undoped single crystals reported in literature results from non-intentional doping by the high impurity level of the source material used. Differences were found in the physical properties between crystals prepared at the upper and the lower phase boundaries of β-FeSi2, indicating that the single crystal properties were significantly influenced by intrinsic defects caused by deviations from the strictly stoichiometric composition and not by extrinsic factors. In contrast to the crystals grown from FeSi/FeSi2 and FeSi2, a new shallow donor state with an activation energy of 23 meV was found in the crystals grown from the FeSi2/Si source.
50 citations
TL;DR: In this article, the electrical transport properties of the p-Sb2S3/n-Si heterojunctions were investigated by current-voltage (I-V) and capacitance voltage (C−V) measurements.
43 citations
TL;DR: In this paper, impurity-doped β-FeSi 2 thin films with boron as p-type and arsenic as n-type dopants were fabricated by sputtering method.
28 citations
TL;DR: In this paper, experimental photoresponses and electrical properties of metal/ beta-FeSi2/Si structures are presented. And the authors compare three kinds of samples: two with a thin epitaxial silicide layer (180 AA), prepared by two different methods, and one with a thick polycrystalline silicide layers (2500 AA).
Abstract: Experimental photoresponses and electrical characteristics of metal/ beta -FeSi2/Si structures are presented. Three kinds of samples are compared: two with a thin epitaxial silicide layer (180 AA), prepared by two different methods, and one with a thick polycrystalline silicide layer (2500 AA). The rectifying behaviour and the photoelectric response of the three kinds of samples are different. In the thin samples these properties are governed by those of the beta -FeSi2/Si interface, whereas for thick samples bulk mechanisms dominate. Analysis of the photocurrent in one kind of thin sample shows that two contributions exist. Their intensities follow similar temperature behaviours but the two transition thresholds do not. These considerations allow assignment of the initial and final states of the transitions, and the upper threshold is shown to correspond to an internal photoemission effect at the beta -FeSi2/Si interface. The conduction band offset is deduced from the difference between the two thresholds. The valence band discontinuity is less than 50 meV between 360 K and 260 K, whereas it changes sign when the temperature decreases below 260 K, the two bandgaps becoming nested within each other. These properties are also discussed for the other kinds of sample and related to the mechanisms which are responsible for the electrical characteristics.
24 citations
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1,131 citations
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TL;DR: In this article, the electrical characteristics of Ge-GaAs heterojunctions, made by depositing Ge epitaxially on GaAs substrates, are described and I-V and electro-optical characteristics are consistent with a model in which the conduction-and valence-band edges at the interface are discontinuous.
Abstract: The electrical characteristics of Ge-GaAs heterojunctions, made by depositing Ge epitaxially on GaAs substrates, are described. I–V and electro-optical characteristics are consistent with a model in which the conduction- and valence-band edges at the interface are discontinuous. The forbidden band in heavily doped (n-type) germanium appears to shift to lower energy values.
970 citations
TL;DR: In this article, X-ray diffraction indicates the films are single-phase, orthorhombic, β-FeSi2, and single-crystal silicon wafers and with low pressure chemical vapor deposition (LPCVD) polycrystalline silicon thin films.
Abstract: Iron disilicide thin films were prepared by furnace reaction of ion beam sputtered iron layers with single‐crystal silicon wafers and with low‐pressure chemical vapor deposition (LPCVD) polycrystalline silicon thin films. X‐ray diffraction indicates the films are single‐phase, orthorhombic, β‐FeSi2. Impurity levels are below the detection limit of Auger spectroscopy. Normal incidence spectral transmittance and reflectance data indicate a minimum, direct energy gap of 0.87 eV. The apparent thermal activation energy of the resistivity in the intrinsic regime is about half of this minimum optical gap. With such a direct band gap, the material may be suitable for the development of both light‐sensitive and light‐emitting thin‐film devices within the silicon microelectronics technology.
447 citations
TL;DR: In this paper, a multi-step recombination-tunnelling model, similar to that used to describe the excess current in tunnel diodes, is developed to explain the observed electrical characteristics of nGe-pGaAs heterodes.
Abstract: A multi-step recombination-tunnelling model, similar to that used to describe the excess current in tunnel diodes, is developed to explain the observed electrical characteristics of nGe-pGaAs heterodiodes. Two different, but quite similar models are used to qualitatively describe the observed forward and reverse characteristics. Quantitative agreement with the experimental characteristics of the many devices presented is obtained by an empirical modification of the resulting equations. The lack of minority carrier injection in these devices is in agreement with the proposed model.
232 citations
TL;DR: In this article, the authors measured the Hall coefficient of β-FeSi2 doped with cobalt (n-type) or aluminium (p-type), and found that the activation energy of the mobility is 0.06 eV, the density of states N = 1.2 × 1022 cm−3.
Abstract: Electrical conductivity, thermoelectric power and Hall coefficient of β-FeSi2 doped with cobalt (n-type) or aluminium (p-type) are measured between 100 and 1200 °K. The conductivity of n-FeSi2 follows an exponential dependence on temperature. The temperature dependence of the thermoelectric power cannot be interpreted on the basis of conduction in a band. With the assumption that conduction in n-FeSi2 is caused by small polarons, the mobility at room temperature is found to be μn = 0.26 cm2/Vs. The activation energy of the mobility is 0.06 eV, the density of states N = 1.2 × 1022 cm−3. The electrical properties of p-FeSi2 can be interpreted using the band model with a hole mobility μp ≈ 2 cm2/Vs, which varies as T−1/2 in the region of extrinsic conduction. From intrinsic conduction a band gap of 0.9 to 1.0 eV is deduced. The disappearance of the thermoelectric power at high temperature is related to the semiconductor-to-metal transition at 1200 °K.
225 citations