Progress towards high power thin film diamond transistors

Looi, Hui Jin; Pang, Lisa Y.S.; Whitfield, Michael D.; Foord, John S.; Jackman, Richard B.

doi:10.1016/s0925-9635(98)00419-1

Cited by 12 publications

(7 citation statements)

References 23 publications

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“…This work presents initial results of the behavior of metal contacts on conductive UNCD, including the influence of acid treatments, work function, and electronegativity of various metals, and a thin interfacial oxide layer.Contacts to conductive diamond films have been fabricated with a wide range of metals. [8][9][10][11] The behavior of these contacts is complex, and seems to depend on a wide range of factors: Type of doping ͑bulk boron doping versus ''p-type surface layer'' on intrinsic diamond͒; morphology ͑homoepitaxial vs. microcrystalline͒; surface termination ͑as-grown vs. oxidizing acid treated͒; and the work function (W) or electronegativity (E n ) of the contact metal. The following cases seem to be typical.…”

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confidence: 99%

“…For ''p-type surface'' conductive diamond films, which rely on a H-terminated surface, Au forms ohmic contacts and Al near-ideal Schottky contacts. 8 For as-grown boron-doped diamond films, no contacts are ohmic without the formation of a carbide or other graphitic interface layer produced via the high-temperature annealing of a carbide-forming metal ͑e.g., Ti or Mo͒; 9,10 with an oxidizing acid cleaning step, contacts become even more rectifying, perhaps due to the removal of any residual ''p-type surface'' conductive layer. Initial work with bulk phosphorous-doped diamond films indicate that ohmic contacts are impossible without the use of an ion bombardment damage step that produces a surface layer of graphite.…”

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confidence: 99%

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Electrical contacts to ultrananocrystalline diamond

Gerbi

Auciello

Birrell

et al. 2003

Applied Physics Letters

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The contact behavior of various metals on n-type nitrogen-doped ultrananocrystalline diamond ͑UNCD͒ thin films has been investigated. The influences of the following parameters on the current-voltage characteristics of the contacts are presented: ͑1͒ electronegativity and work function of various metals, ͑2͒ an oxidizing acid surface cleaning step, and ͑3͒ oxide formation at the film/contact interface. Near-ideal ohmic contacts are formed in every case, while Schottky barrier contacts prove more elusive. These results counter most work discussed to date on thin diamond films, and are discussed in the context of the unique grain-boundary conductivity mechanism of the nitrogen-doped UNCD.Diamond thin films are a promising platform material for a large number of electronic applications, including chemical sensors, 1 bioimplantable electronics, and high-power radiation hard field effect transistors. However, many limitations exist which hinder the commercial application of diamond films, for example: High cost, lack of reliable n-type doping, high surface roughness, and high film stress. In addition, a crucial limitation for the materials integration of diamond is the lack of reliable low contact resistance ohmic contacts which can be fabricated at low temperatures.Ultrananocrystalline diamond ͑UNCD͒ films have a set of unique structural and tribological characteristics which obviate many of the limitations just mentioned. 2-6 Deposited via microwave plasma-enhanced chemical vapor deposition ͑MPECVD͒ with unique Ar-rich plasma chemistries, UNCD is an extremely fine-grained ͑2-5 nm͒, smooth ͑24 nm rootmean-square roughness͒, 98% sp 3 diamond film with atomically abrupt grain boundaries. Strikingly, UNCD films can be doped with nitrogen to produce very highly conductive n-type diamond, 3 which is fully active at room temperature and demonstrates reasonable mobilities. Substitutional donor nitrogen in bulk diamond does not result in conduction due to its 1.7 eV activation energy, but the mechanism of nitrogen doping in UNCD is quite different. Theoretical calculations 7 indicate that nitrogen is preferentially incorporated into grain boundaries, which consist of a combination of sp 2 , sp 3 , and other bonded carbon. This nitrogen is energetically favored to form bonding states which result in a lone electron pair and a carbon dangling bond, promoting grain boundary conductivity. The conductivity of nitrogendoped UNCD is correlated with the amount of nitrogen in the films as measured by high mass resolution secondary ion mass spectroscopy. Initial measurements indicate a roomtemperature conductivity of 140 ⍀ Ϫ1 cm Ϫ1 at a nitrogen content of 0.2 at. %. Temperature dependent conductivity measurements indicate a range of thermally activated conduction mechanisms. 3 The conductive UNCD/contact system is thus a complicated one, as the grain boundaries-not diamond grainsform the conductive pathways. The same electrically active states which promote conduction may exist in significant numbers at the UNCD/contact interface, st...

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confidence: 99%

mentioning

confidence: 99%

Electrical contacts to ultrananocrystalline diamond

Gerbi

Auciello

Birrell

et al. 2003

Applied Physics Letters

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“…Another important issue for characterizing CVD diamond films comes with forming ohmic and Schottky contacts. Investigations of contact behaviour of various metals on ntype nitrogen doped ultra nanocrystalline diamond (UNCD) thin films [181] and characterization of diamond ohmic and Schottky contacts is performed in [159,182]. It was shown that near-ideal ohmic contacts are formed in every case, while Schottky barrier contacts prove more elusive.…”

Section: Diamondmentioning

confidence: 99%

“…The maximal transconductance of 100 mS mm −1 , cutoff frequency of 11 GHz and maximal frequency of oscillations of 18 GHz were obtained in the 0.7 µm gate-length diamond MESFETs fabricated on the H-terminated diamond surface [182,191]. A small-signal equivalent circuit for this device was developed, by matching the measured S-parameters with the calculated ones.…”

Section: Diamond Bjt and Fetsmentioning

confidence: 99%

Wide gap semiconductor microwave devices

Buniatyan

Aroutiounian

2007

J. Phys. D: Appl. Phys.

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A review of properties of wide gap semiconductor materials such as diamond, diamond-like carbon films, SiC, GaP, GaN and AlGaN/GaN that are relevant to electronic, optoelectronic and microwave applications is presented.We discuss the latest situation and perspectives based on experimental and theoretical results obtained for wide gap semiconductor devices. Parameters are taken from the literature and from some of our theoretical works. The correspondence between theoretical results and parameters of devices is critically analysed.

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“…Polycrystalline diamond is one of the best candidates for high power-high temperature electronic devices [1] especially Schottky diodes, field emitters and field effect transistors. Some published works show also a potential application in photodiodes [2] in near UV-visible spectrum region [3].…”

Section: Introductionmentioning

confidence: 99%