In this paper we present photoluminescence, photoreflectance, and absorbance measurements on silicon samples with β-FeSi 2 precipitates, as structurally characterized in the first part of this paper [M. G. Grimaldi et al., Phys. Rev. B 66, 085319 (2002)]. By comparing the photoluminescence measurements in different experimental conditions and with excitation energy above and below the silicon threshold, by considering the direct gap estimations by photoreflectance and absorption, we argue that the 1.54 μm photoluminescence peak in the spectra is produced by an indirect transition in the disc-shaped precipitates. However, the latter ones are predicted to be the most efficient configuration, acting as a trapping well for carriers generated in the silicon matrix, and displaying a high structural quality with no dangling bonds at the β-FeSi 2 /Si interface. Our simple model, based on band lineup at the interface, is also able to explain the temperature quenching of the photoluminescence peak.

Luminescence from beta-FeSi2 precipitates in Si. II: Origin and nature of the photoluminescence

Electronic properties of semiconducting silicides: fundamentals and recent predictions

Photovoltaic properties of ion-beam synthesized β-FeSi2/n-Si heterojunctions

Amorphous iron silicide was reported to be semiconducting as well as β-FeSi2, and it has received considerable attention from both the physical and engineering points of view However, there have been few studies and its basic properties are still unknown We could grow the semiconducting nanocrystalline iron disilicide thin films by pulsed-laser deposition using an FeSi2 target They consist of crystallites with diameters ranging from 3 to 5 nm The carrier density and the mobility at 300 K were 15×1019 cm−3 and 35 cm/V s, respectively

Semiconducting nanocrystalline iron disilicide thin films prepared by pulsed-laser ablation

Important research targets to be explored for β-FeSi2 device making

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.

https://iopscience.iop.org/article/10.1088/0268-1242/9/7/018/pdf

Band discontinuities at beta -FeSi2/Si heterojunctions as deduced from their photoelectric and electrical properties

Properties of semiconducting rhenium silicide thin films grown epitaxially on silicon (111)

Unprecedented Hall mobility, electron concentration and photoconductivity are demonstrated in semiconducting - thin films prepared on Si(111) surfaces by co-sputtering of iron and silicon followed by post-anneal. Characterization of the silicide as a function of the initial temperature and post-treatment shows that annealing temperatures above C are needed to obtain single phase -. Reactive deposition on substrates heated at C leads to textured films. Majority carriers are electrons in all these unintentionally doped films. Hall concentrations between and electrons and respective Hall mobilities from 290 to are measured at room temperature, involving two different conduction band minima in these two extreme cases. Only deep centres exist in the samples having the lower carrier concentration. In such a situation, raw data must be corrected for the substrate contribution to extract values which are relevant for the - film alone. Photoconductivity also takes place in these samples: at 80 K, it shows a maximum value at the direct band gap of - while at 296 K a step still appears at the same energy. Such results are a consequence of the important decrease of the residual impurity concentration in comparison to values previously published.

http://iopscience.iop.org/article/10.1088/0268-1242/13/10/020/pdf

Semiconducting iron silicide thin films on silicon (111) with large Hall mobility and low residual electron concentration

Electrical transport properties of semiconducting rhenium silicide thin films are investigated. This silicide, which shows a commensurable fit with the (111) surface of silicon, has been epitaxially grown on such substrates by reactive deposition at 650 °C. A first kind of sample has been annealed at 750 °C under ultra-high vacuum. A second kind of sample has been annealed at 850 °C under partial pressure of hydrogen. Measurements of conductivity and the Hall effect have been performed in thin films prepared on highly resistive silicon substrates. The silicide appears as a p-type semiconductor for the first kind of sample and n-type for the second one. However, the intrinsic regime is almost reached near room temperature. Electron mobility for the second kind of sample is at least 200 cm2 V-1s-1 at ambient temperature and in excess of 1000 cm2 V-1s-1 at liquid-nitrogen temperature. The forbidden bandgap deduced from the thermal activation of carrier concentrations in the nearly intrinsic regimes is 0.28 eV. These facts indicate that the rhenium silicide thin films quality has been dramatically improved by the aforementioned thermal treatments in comparison to previous reports on thin films.

Electrical transport properties of semiconducting rhenium silicide thin films on silicon(111)

Transport properties of semiconducting β-FeSi2 thin films obtained by co-sputtering of iron and silicon and post-anneal are investigated. In these polycrystalline thin films, majority carriers are electrons and their Hall mobility can reach values of 900 cm2/V s at room temperature. Conductivity, Hall effect and photoconductivity of unintentionally doped silicide thin films are studied. The results obtained in two of them are presented, because they are representative of the extreme values found for the Hall concentration. They turn out to be, respectively, 1.8×1017 and 6×1015 electrons cm−3 at room temperature. In addition to shallow donors present only in the first sample, deeper centers show ionization energy of 0.11 and 0.23 eV, respectively. For the second sample, the substrate contribution has to be considered for extracting values which are relevant for the β-FeSi2 film alone. Photoconductivity takes place in these samples: at 80 K, it shows a maximum value at 0.86–0.87 eV, which correlates well wi...

P Muret

Papers

Band discontinuities at beta -FeSi2/Si heterojunctions as deduced from their photoelectric and electrical properties

Properties of semiconducting rhenium silicide thin films grown epitaxially on silicon (111)

Semiconducting iron silicide thin films on silicon (111) with large Hall mobility and low residual electron concentration

Electrical transport properties of semiconducting rhenium silicide thin films on silicon(111)

Transport properties of unintentionally doped iron silicide thin films on silicon(111)