Technical Papers
An impedance spectroscopic investigation of the electrical properties of delta-doped diamond structu
Impedance spectroscopy has been used to investigate the conductivity displayed by diamond doped with boron in an intrinsic-∂-layer-intrinsic multilayer system with differing ∂-layer thicknesses. Carrier transport within 5nm ∂-layer structures is complex, being dominated by conduction in the interfacial regions between the ∂-layer and the intrinsic regions, as well as conduction within the ∂-layer itself. In the case of 3.2 nm thick ∂-layers the situation appears improved with uncapped samples supporting only two conduction paths, one of which may be associated with transport outside the ∂-layer, the other low transport within the ∂-layer complex diamond structures. Introduction of the capping layer creates a third conduction within the ∂-layer associated with unwanted boron in the capping layer-∂-layer interface. Copyright 2009 American Institute of Physics [doi:10.1063/1.3261759]
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CVD Diamond MESFETs - technology and applications
2nd International Industrial Diamond Conference, 2007
Authors: R. Lang, C. Wort, R. Balmer, I. Friel, G. Scarsbrook
Abstract
Current semiconducting materials (Si and GaAs) are limited in the power (or power density) that they can offer for the next generation of high-power microwave sub-systems. Such systems are likely to require compact, low-mass, low-cost, reliable solutions for a range of applications that, perhaps, to date have been dominated by Travelling Wave Tubes (TWTs). Wide band gap materials such as GaN, SiC and diamond all offer substantial potential for such RF devices, with diamond having by far the best combination of material characteristics.
Photoionization measurement of deep defects in single-crystalline CVD diamond using the transient-cu
Published in Physical Review B73, 245207 (2006)
Authors: Jan Isberg, Antonella Tajani and Daniel Twitchen
Abstract
The researchers have adopted the transient-current technique as a sensitive method to detect small concentrations of charted defects in diamond and to study its photoionization spectrum. It is found that ionized impurity concentrations in the interval 10-9 - 10-13 cm-3 can readily be detected in diamond. By continuously measuring the charge concentration by illuminating the the samples with monochromatic light, the evolution of the charge state of the dominating defect can be continuously monitored. The team has obtained the photoionization cross-section spectrum from the dominant deep defect in single-crystalline chemical vapour deposition (CVD) diamond using this method.
Diamond-MESFETs - Synthesis and Integration
2nd European Radar Conference, 2005,
Authors: M. Schwetters, M.P. Dixon, A. Tajani, D.J. Twitchen, S.E. Coe, H. El-Haji, M. Kubovic, M. Neuburger, A. Kaiser and E. Kohn.
Abstract
The authors report on the utilization of synthetic diamond grown by chemical vapour deposition (CVD) for use as metal semiconductor field effect transistors (MESFETs). The lack of a shallow n-type donor means that diamond-based electronic devices are unipolar (p-type). The devices presented in this paper are based on delta-doping. Delta-doping stands for the use of very thin (<5 nm) highly doped NA > 1020 cm-3 buried layers. This approach poses a huge challenge in terms of synthesis as well as processing. First successful attempts of fully integrating working delta-doped diamond MESFETs are presented.
Numerical and Experimental Analysis of Single Crystal Diamond Schottky Barrier Diodes
Proceedings of the 17th International Symposium on Power Semiconductor Devices and ICs.
Authors: S.J. Rashid, L. Couldbeck, A. Tajani, M. Brezeannu, A. Garraway, T. Butler, N.L. Rupesinghe, D.J. Twitchen, G.A.J. Amaratunga, F. Udrea, P. Taylor, M. Dixon and J. Isberg.
Abstract
The team presented its findings on the numerical and experimental analysis of diamond Schottky Barrier diodes comprising intrinsic single crystal chemical vapour deposited (CVD) diamond layers growing on highly boron doped substrates also grown by CVD. Good correlation with experimental results has been achieved through numerical modelling that has incorporated previously data on transport physics and carrier activitation. With the numerical model, the group was able to match to within 12 – 15% of the measured forward characteristics of fabricated diamond Schottky Barrier Diodes up to 2 V in excess of the turn on voltage, for two different Schottky metals.
Temperature dependence of hold drift mobility in high-purity single-crystal CVD diamond.
Published in Phys.stat.sol.(a), 202 (2005) 2194-2198
Authors: Jan Isberg, Adam Lindblom, Antonella Tajana and Daniel Twitchen
Abstract
Hold transport properties in high-purity single crystal CVD diamond samples were studied using the time of flight technique with optical excitation of the carriers. The measurements were taken at different temperatures in the interval 80-470 K. By varying the intensity of the optical excitation over several orders of magnitude, measurements at different carrier concentrations have been performed. In this way, measurements have been made both in the space charge liminted and non spaced charge limited regimes, with consistent results. The temperature dependence of the low-field hold drift mobility shows a Tα dependence with α = -1.5, below 350 K. This indicates that acoustic phonon scattering is the dominant scattering mechanism and a very low concentration of ionized impurities in this material.
High-Voltage Single Crystal Diamond Diodes
Demonstration of a 2.5 kV diamond diode is provided by electrical measurements using a circular gold Schottky contact, with an area >1 mm2, on a large area freestanding single-crystal diamond consisting of a thin high purity layer (<1 x 1013 [B]/cm3) on a thicker heavily doped (>1 x 1019 [B]cm3) The diode structures were fabricated using a microwave-assisted chemical vapour deposition process. The forward properties of the diode show a space charged limited current, with a forward-voltage drop of 2 V and a hole mobility of 4100 ± 400cm2/Vs at room temperature. For temperatures between 300K
High Carrier Mobility in Single-Crystal Plasma-Deposited Diamond
Science 297, 1670-1672 (2002).
Authors: J. Isberg, J. Hammersberg, E. Johansson, T. Wikstrom, D.J. Twitchen, A.J. Whitehead, S.E. Coe, G.A. Scarsbrook.
Abstract
Room-temperature drift mobilities of 4500 cm2 V-1s-1 for electronics and 3800 cm2 V-1s-1 for holes have been measured in high-purity single-crystal diamond grown using a chemical vapour deposition process. The low-field drift mobility values were determined by using the time-of-flight technique on thick, intrinsic, freestanding diamond plates and were verified by current-voltage measurements on p-i junction diodes. The improvement of the electronic properties of single-crystal diamond and the reproducibility of those properties are encouraging for research on, and development of, high performance diamond electronics.