Stability of Operation of Atmosphere-Exposed, Hydrogen-Terminated Diamond FETs under Constant Operation

Macdonald, D. A., Tallaire, A., Verona, C., Limiti, E. and Moran, D. A. J. (2015) Stability of Operation of Atmosphere-Exposed, Hydrogen-Terminated Diamond FETs under Constant Operation. In: MRS Fall Meeting: Materials Research Society, Boston MA, USA, 29 Nov - 4 Dec 2015,

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Diamond is an interesting material for high power FET fabrication owing to its high breakdown field of >10MVcm-1[1] and high thermal conductivity of 22Wcm-1K-1[2]. It is also suited for operation in extreme environments due to its robustness, chemical inertness and radiation resistance [3]. For high power operation achieving a large output current at a large operation voltage is desirable. Any mechanisms therefore that result in reduced output current at maximum drain bias voltage would be detrimental to device performance. Hydrogen terminated diamond FETs take advantage of surface transfer doping using atmospheric adsorbates as a charge transfer layer resulting in the formation of a 2DHG channel below the diamond surface. This has been shown to be unstable, with atmospheric adsorbates sublimating from the surface around 200 °C [4]. Variations in the properties of the charge transfer layer can result in diminished carrier concentration reducing current transport through the device. This work presents the DC response with time of both un-gated and gated (FET) structures on hydrogen terminated single crystal diamond under constant voltage biases. It is believed that this is the first study of this kind pertaining to the stability of diamond FETs. Degradation of current over extended periods of constant operation has been observed experimentally. The nature of the observed IV response of both un-gated and gated structures appears to be an inverse exponential decrease of up to 10% in 10 minutes of continuous operation. It is suggested that the method of current degradation is due to charging of the structures with positive charge as a result of charge trapping. As a similar response is achieved from both un-gated and gated structures it is also proposed this trapping happens at the interface between surface adsorbate and diamond surface. Extended operation can result in increased temperature of the structures, however diamond’s high thermal conductivity could counter act this by dissipating heat effectively, although it appears this has not yet been verified experimentally. This investigation will continue with varying gate and drain biases to determine the whether the reduction is determined by the magnitude of potential across the device. Devices of different widths will also be tested to determine if the absolute non-normalized current is a factor in total current reduction.

Item Type:Conference Proceedings
Glasgow Author(s) Enlighten ID:Moran, Professor David
Authors: Macdonald, D. A., Tallaire, A., Verona, C., Limiti, E., and Moran, D. A. J.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering

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