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Negative electron mobility in diamond
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Element Six Ltd,Ascot, Berkshire, UK.
2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 17, 172103- p.Article in journal (Refereed) Published
Abstract [en]

By measuring the drift velocity of electrons in diamond as a function of applied electric field, wedemonstrate that ultra-pure diamond exhibits negative differential electron mobility in the [100] directionbelow 140 K. Negative electron mobility is normally associated with III–V or II–VI semiconductors withan energy difference between different conduction band valleys. The observation of negative mobility indiamond, an elemental group IV semiconductor, is explained in terms of repopulation effects betweendifferent equivalent conduction band valleys using a model based on the Boltzmann equation.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2012. Vol. 100, no 17, 172103- p.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
URN: urn:nbn:se:uu:diva-173582DOI: 10.1063/1.4705434ISI: 000303340300034OAI: oai:DiVA.org:uu-173582DiVA: diva2:524556
Available from: 2012-05-02 Created: 2012-04-29 Last updated: 2015-12-04Bibliographically approved
In thesis
1. Experimental Studies of Charge Transport in Single Crystal Diamond Devices
Open this publication in new window or tab >>Experimental Studies of Charge Transport in Single Crystal Diamond Devices
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a promising material for high-power, high-frequency and high- temperature electronics applications, where its outstanding physical properties can be fully exploited. It exhibits an extremely high bandgap, very high carrier mobilities, high breakdown field strength, and the highest thermal conductivity of any wide bandgap material. It is therefore an outstanding candidate for the fastest switching, the highest power density, and the most efficient electronic devices obtainable, with applications in the RF power, automotive and aerospace industries. Lightweight diamond devices, capable of high temperature operation in harsh environments, could also be used in radiation detectors and particle physics applications where no other semiconductor devices would survive.

The high defect and impurity concentration in natural diamond or high-pressure-high-temperature (HPHT) diamond substrates has made it difficult to obtain reliable results when studying the electronic properties of diamond. However, progress in the growth of high purity Single Crystal Chemical Vapor Deposited (SC-CVD) diamond has opened the perspective of applications under such extreme conditions based on this type of synthetic diamond.

Despite the improvements, there are still many open questions. This work will focus on the electrical characterization of SC-CVD diamond by different measurement techniques such as internal photo-emission, I-V, C-V, Hall measurements and in particular, Time-of-Flight (ToF) carrier drift velocity measurements. With these mentioned techniques, some important properties of diamond such as drift mobilities, lateral carrier transit velocities, compensation ratio and Schottky barrier heights have been investigated. Low compensation ratios (ND/NA) < 10-4 have been achieved in boron-doped diamond and a drift mobility of about 860 cm2/Vs for the hole transit near the surface in a lateral ToF configuration could be measured. The carrier drift velocity was studied for electrons and holes at the temperature interval of 80-460 K. The study is performed in the low-injection regime and includes low-field drift mobilities. The hole mobility was further investigated at low temperatures (10-80 K) and as expected a very high mobility was observed.

In the case of electrons, a negative differential mobility was seen in the temperature interval of 100-150K. An explanation for this phenomenon is given by the intervally scattering and the relation between hot and cold conduction band valleys. This was observed in direct bandgap semiconductors with non-equivalent valleys such as GaAs but has not been seen in diamond before.

Furthermore, first steps have been taken to utilize diamond for infrared (IR) radiation detection. To understand the fundamentals of the thermal response of diamond, Temperature Coefficient of Resistance (TCR) measurements were performed on diamond Schottky diodes which are a candidate for high temperature sensors. As a result, very high TCR values in combination with a low noise constant (K1/f) was observed.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 67 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 944
Single crystal diamond, carrier transport, CVD diamond, time-of-flight, mobility, IR detector, compensation, diamond diode, drift velocity, thermal detector
National Category
Engineering and Technology
urn:nbn:se:uu:diva-173599 (URN)978-91-554-8391-3 (ISBN)
Public defence
2012-06-05, Häggsalen, Lägerhyddsvägen 1, Ångströmlaboratoriet, Uppsala, 13:15 (English)
Available from: 2012-05-15 Created: 2012-05-01 Last updated: 2013-01-07Bibliographically approved

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