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Charge Transport in Single-crystalline CVD Diamond
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Diamond electronics)
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. , p. 87
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 746
Keywords [en]
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
Identifiers
URN: urn:nbn:se:uu:diva-122794ISBN: 978-91-554-7815-5 (print)OAI: oai:DiVA.org:uu-122794DiVA, id: diva2:311093
Public defence
2010-06-04, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2010-05-12 Created: 2010-04-20 Last updated: 2010-05-18Bibliographically approved
List of papers
1. Transient current electric field profiling of single crystal CVD diamond
Open this publication in new window or tab >>Transient current electric field profiling of single crystal CVD diamond
2006 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 21, no 8, p. 1193-1195Article in journal (Refereed) Published
Abstract [en]

The transient current technique ( TCT) has been adapted for profiling of the electric field distribution in intrinsic single crystal CVD diamond. It was found that successive hole transits do not appreciably affect the electric field distribution within the sample. Transits of holes can therefore be used to probe the electric field distribution and also the distribution of trapped charge. Electron transits, on the other hand, cause an accumulation of negative charge in the sample. Illumination with blue or green light was shown to lead to accumulation of positive charge. Low concentrations of trapped charge can be detected in diamond using TCT, corresponding to an ionized impurity concentration below N = 10(10) cm(-3).

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-22417 (URN)10.1088/0268-1242/21/8/035 (DOI)000240123100036 ()
Available from: 2007-01-23 Created: 2007-01-23 Last updated: 2017-12-07Bibliographically approved
2. High-field Electrical Transport in Single Crystal CVD Diamond Diodes
Open this publication in new window or tab >>High-field Electrical Transport in Single Crystal CVD Diamond Diodes
2006 (English)In: Advances in Science and Technology, Vol. 48, p. 73-76Article in journal (Refereed) Published
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-22412 (URN)
Available from: 2007-01-23 Created: 2007-01-23 Last updated: 2015-12-10
3. Formation of secondary electron cascades in single-crystalline plasma-deposited diamond upon exposure to femtosecond x-ray pulses
Open this publication in new window or tab >>Formation of secondary electron cascades in single-crystalline plasma-deposited diamond upon exposure to femtosecond x-ray pulses
Show others...
2008 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, no 6, article id 064909Article in journal (Refereed) Published
Abstract [en]

Secondary electron cascades were measured in high purity single-crystalline chemical vapor deposition (CVD) diamond, following exposure to ultrashort hard x-ray pulses (140 fs full width at half maximum, 8.9 keV energy) from the Sub-Picosecond Pulse Source at the Stanford Linear Accelerator Center. We report measurements of the pair creation energy and of drift mobility of carriers in two CVD diamond crystals. This was done for the first time using femtosecond x-ray excitation. Values for the average pair creation energy were found to be 12.17 +/- 0.57 and 11.81 +/- 0.59 eV for the two crystals, respectively. These values are in good agreement with recent theoretical predictions. The average drift mobility of carriers, obtained by the best fit to device simulations, was mu(h)= 2750 cm(2)/V s for holes and was mu(e)= 2760 cm(2) / V s for electrons. These mobility values represent lower bounds for charge mobilities due to possible polarization of the samples. The results demonstrate outstanding electric properties and the enormous potential of diamond in ultrafast x-ray detectors.

National Category
Physical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-110448 (URN)10.1063/1.2890158 (DOI)000254536900143 ()
Available from: 2009-11-16 Created: 2009-11-16 Last updated: 2017-12-12Bibliographically approved
4. Compensation in boron-doped CVD diamond
Open this publication in new window or tab >>Compensation in boron-doped CVD diamond
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2008 (English)In: Physica status solidi. A, Applications and Materials Science, ISSN 1862-6300, Vol. 205, no 9, p. 2190-2194Article in journal (Refereed) Published
Abstract [en]

Hall-effect measurements on single crystal boron-doped CVD diamond in the temperature interval 80-450 K are presented together with SIMS measurements of the dopant concentration. Capacitance-voltage measurements on rectifying Schottky junctions manufactured on the boron-doped structures are also presented in this context. Evaluation of the compensating donor (N-D) and acceptor concentrations (N-A) show that in certain samples very low compensation ratios (N-D/N-A below 10(-4)) have been achieved. The influence of compensating donors on majority carrier transport and the significance for diamond device performance are briefly discussed.

National Category
Materials Engineering Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-107876 (URN)10.1002/pssa.200879711 (DOI)000259653700017 ()
Available from: 2009-08-31 Created: 2009-08-31 Last updated: 2017-01-25
5. A lateral time-of-flight system for charge transport studies
Open this publication in new window or tab >>A lateral time-of-flight system for charge transport studies
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2009 (English)In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 18, no 9, p. 1163-1166Article in journal (Refereed) Published
Abstract [en]

A measurement system for lateral ToF charge carrier transport studies in intrinsic diamond is described. In the lateral ToF geometry, carriers travel close to the sample surface and the system is therefore particularly suited for studies of thin layers as well as the influence of different surface conditions on transport dynamics. A 213nm pulsed UV laser is used to create electron-hole pairs along a line focus between two parallel metal electrodes on one surface. The use of reflective UV-optics with short focal length allows for a narrow focal line and also for imaging the sample in UV or visible light without any dispersion. A clear hole transit was observed in one homoepitaxial single crystalline diamond film for which the substrate was treated by a Ar/Cl plasma etch prior to deposition. The hole transit signal was sufficiently clear to measure the near-surface hole drift mobility of about 860cm2/Vs across a contact spacing of 0.3mm.

Place, publisher, year, edition, pages
Langford Lane, Kidlington, Oxford, OX5 1GB, United Kingdom: Elsevier Ltd, 2009
Keywords
Mobility, Time-of-Flight, CVD diamond, Single crystal diamond
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113146 (URN)10.1016/j.diamond.2009.03.002 (DOI)000268610700020 ()09259635 (ISBN)
Note

Compilation and indexing terms, Copyright 2009 Elsevier Inc. 20092812180300 Charge transport CVD diamond Electron hole pairs Focal lengths Homoepitaxial Line-focus Measurement system Metal electrodes Mobility Near-surface Plasma etch Pulsed UV-lasers Sample surface Single crystal diamond Single-crystalline diamond Surface conditions Thin layers Time-of-Flight Time-of-flight system Transport dynamics Visible light

Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
6. Negative differential electron mobility and single valley transport in diamond
Open this publication in new window or tab >>Negative differential electron mobility and single valley transport in diamond
(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.

Keywords
ToF, time of flight, negative differential mobility, drift velocity, CVD diamond, single crystal diamond
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-122793 (URN)
Available from: 2010-04-20 Created: 2010-04-20 Last updated: 2015-12-04
7. Electron and hole drift velocity in chemical vapor deposition diamond
Open this publication in new window or tab >>Electron and hole drift velocity in chemical vapor deposition diamond
2011 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 6, p. 063719-Article in journal (Refereed) Published
Abstract [en]

The time-of-flight technique has been used to measure the drift velocities for electrons and holes in high-purity single-crystalline CVD diamond. Measurements were made in the temperature interval 83 ≤ T ≤ 460 K and for electric fields between 90 and 4 × 103 V/cm, applied in the <100> crystallographic direction. The study includes low-field drift mobilities and is performed in the low-injection regime to perturb the applied electric field only minimally.

Keywords
velocity, time-of-flight, carrier drift mobility, single crystal diamond
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics; Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-122792 (URN)10.1063/1.3554721 (DOI)000289149900072 ()
Funder
Swedish Research Council
Available from: 2011-04-09 Created: 2010-04-20 Last updated: 2017-12-12Bibliographically approved

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