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Negative differential electron mobility and single valley transport 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.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Electron transport in isolated conduction band valleys across macroscopic distances has been observed in single-crystalline CVD diamond at 70 K by use of the time-of-flight technique. This is possible due to the very low scattering cross section for intervalley scattering in single-crystalline CVD diamond. This effect enables a precise determination of the ratio between longitudinal and transverse conduction band effective masses in diamond. We find ml/mt = 5.2. At  temperatures in the interval 110-140 K, a negative differential mobility (NDM) has been observed for electrons with the electric field parallel to the crystallographic <100> direction.  The NDM can be explained in terms of valley repopulation effects between the equivalent energy conduction band minima.

Keyword [en]
ToF, time of flight, negative differential mobility, drift velocity, CVD diamond, single crystal diamond
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-122793OAI: oai:DiVA.org:uu-122793DiVA: diva2:311067
Available from: 2010-04-20 Created: 2010-04-20 Last updated: 2015-12-04
In thesis
1. Charge Transport in Single-crystalline CVD Diamond
Open this publication in new window or tab >>Charge Transport in Single-crystalline CVD Diamond
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a semiconductor with many superior material properties such as high breakdown field, high saturation velocity, high carrier mobilities and the highest thermal conductivity of all materials. These extreme properties, as compared to other (wide bandgap) semiconductors, make it desirable to develop single-crystalline epitaxial diamond films for electronic device and detector applications. Future diamond devices, such as power diodes, photoconductive switches and high-frequency field effect transistors, could in principle deliver outstanding performance due to diamond's excellent intrinsic properties. However, such electronic applications put severe demands on the crystalline quality of the material.

Many fundamental electronic properties of diamond are still poorly understood, which severely holds back diamond-based electronic device and detector development. This problem is largely due to incomplete knowledge of the defects in the material and due to a lack of understanding of how these defects influence transport properties.

Since diamond lacks a shallow dopant that is fully thermally activated at room temperature, the conventional silicon semiconductor technology cannot be transferred to diamond devices; instead, new concepts have to be developed. Some of the more promising device concepts contain thin delta-doped layers with a very high dopant concentration, which are fully activated in conjunction with undoped (intrinsic) layers where charges are transported. Thus, it is crucial to better understand transport in high-quality undoped layers with high carrier mobilities.

The focus of this doctoral thesis is therefore the study of charge transport and related electronic properties of single-crystalline plasma-deposited (SC-CVD) diamond samples, in order to improve knowledge on charge creation and transport mechanisms. Fundamental characteristics such as drift mobilities, compensation ratios and average pair-creation energy were measured. Comparing them with theoretical predictions from simulations allows for verification of these models and improvement of the diamond deposition process.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 87 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 746
CVD diamond, wide-bandgap semiconductor, single-crystalline diamond, carrier transport, time-of-flight, drift velocity, mobility, compensation, pair-creation, electronic devices, diamond detector, diamond diode
urn:nbn:se:uu:diva-122794 (URN)978-91-554-7815-5 (ISBN)
Public defence
2010-06-04, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2010-05-12 Created: 2010-04-20 Last updated: 2010-05-18Bibliographically approved

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