Abstract:International audienceThe temperature dependence of the hole sheet density and mobility of four capped delta boron doped [100]-oriented epilayers has been investigated experimentally and theoretically over a large temperature range (6K < T < 500 K). The influence of the parallel conduction through the thick buffer layer overgrown on the diamond substrate was shown not to be negligible near room temperature. This could lead to erroneous estimates of the hole mobility in the delta layer. None of the delta-layers… Show more
“…14,15 Hall effect combined to four probe resistivity measurements have also been used to evaluate the sheet density (p S ) and the carrier mobility (l H ). [15][16][17][18] A low sheet carrier density p S ' 10 13 cm À2 and a hole mobility l H ¼ 13 cm 2 / V.s at room temperature in delta structures grown on [111]-oriented diamond substrates were reported, 15 but unfortunately, no temperature dependence of p S and l H in delta structures was shown for the same samples. One of the recent works reported a very low mobility at low temperature (l H $ 1 cm 2 /V.s at T ¼ 100 K) and a high mobility at room temperature (l H $ 900 cm 2 /V.s).…”
Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2 nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called delta-doped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6 K < T < 450 K). Depending on the sample, metallic or non-metallic behavior was observed. A hopping conduction mechanism with an anomalous hopping exponent was detected in the non-metallic samples. All metallic delta-doped layers exhibited the same mobility value, around 3.6 ± 0.8 cm2/Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2 nm
“…14,15 Hall effect combined to four probe resistivity measurements have also been used to evaluate the sheet density (p S ) and the carrier mobility (l H ). [15][16][17][18] A low sheet carrier density p S ' 10 13 cm À2 and a hole mobility l H ¼ 13 cm 2 / V.s at room temperature in delta structures grown on [111]-oriented diamond substrates were reported, 15 but unfortunately, no temperature dependence of p S and l H in delta structures was shown for the same samples. One of the recent works reported a very low mobility at low temperature (l H $ 1 cm 2 /V.s at T ¼ 100 K) and a high mobility at room temperature (l H $ 900 cm 2 /V.s).…”
Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2 nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called delta-doped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6 K < T < 450 K). Depending on the sample, metallic or non-metallic behavior was observed. A hopping conduction mechanism with an anomalous hopping exponent was detected in the non-metallic samples. All metallic delta-doped layers exhibited the same mobility value, around 3.6 ± 0.8 cm2/Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2 nm
“…A very recent letter published while this paper was in review also reports temperature dependent Hall mobility in delta doped boron diamond which they also explain as a two channel conduction process [38].…”
Boron delta-doped diamond structures have been synthesized using microwave plasma chemical vapor deposition, and fabricated into FET and gated Hall bar devices for assessment of the electrical characteristics. A detailed study of variable temperature Hall, conductivity and field-effect mobility measurements was completed. This was supported by Schrödinger-Poisson and relaxation time calculations based upon application of Fermi's golden rule. A two carrier-type model was developed with an activation energy of ~0.2 eV between the delta layer lowest subband with mobility ~1 cm 2 /Vs and the bulk valence band with high mobility. This new understanding of the transport of holes in such boron delta-doped structures has shown that although Hall mobility as high as 900 cm 2 /Vs was measured at room temperature, this dramatically overstates the actual useful performance of the device.a Corresponding author
“…Note that for thicker layers (sample A) the difference is not so critical in contrast to thinner layers (#4 sample A and sample B). Such behavior motivated other authors to use complementary techniques to improve the SIMS profile; Chicot et al 27 calculate this broadening to correct the experimental data while Balmer et al 28 complete the SIMS data with elastic recoil detection analysis (ERDA) to estimate boron-doping thickness. Here, as a first result, a 5 nm-thick layer is demonstrated directly by the HAADF-STEM profile, showing that the growth technology is now close to reach quantum confinement enhancement of mobility.…”
To develop further diamond related devices, the concentration and spatial location of dopants should be controlled down to the nanometer scale. Scanning transmission electron microscopy using the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 1020 cm−3 were quantitatively derived down to nanometer resolution from the signal dependence on thickness and boron content. Experimental boron local doping profiles measured on diamond p−/p++/p− multilayers are compared to macroscopic profiles obtained by secondary ion mass spectrometry, avoiding reported artefacts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.