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Communication Dans Un Congrès Année : 2016

Optimal design of unipolar diamond power devices: drift region and channel dose

Résumé

As the demand in high power and high frequency electronics keep increasing, former semiconductors show their limits. Indeed, components able to operate at high voltage, high frequency and high temperature are crucial in order to go beyond the classical design trade off in power devices. Diamond, thanks to its outstanding properties, is the ultimate semiconductor to meet these requirements [1]. Schottky Barrier Diode (SBD) and Field Effect Transistor (FET) are two complementary switches in the commutation cell of power converters. Diamond SBDs able to withstand up to 10 kV have been already reported [2,3] and diamond FETs are under investigation through MESFET [4] or MOS capacitor [5]. Nevertheless to take benefit of diamond superlative properties of such components, a particular attention has to be paid to the design of the structure. In this work we have focused on the optimization of the Ron.S(BV) figure of merit while sizing the drift layer of unipolar High Voltage diamond power devices. The optimal drift layer parameters were considered as a function of the targeted breakdown voltage and of the temperature by using a one dimensional semi-analytical approach of the breakdown voltage [6]. Moreover and in the case of diamond FETs, an analytical approach was used to determine the minimum channel dose (doping level times thickness) ensuring a good operating regime for diamond p-MOSFET. Based on the ionization integral calculation with diamond adapted impact ionization coefficients [7], we performed an accurate analysis of the reciprocal punch through (PT) factor of a unipolar component as function of the breakdown voltage (from 1kV to 10kV). Therefore we determined the optimal reciprocal PT coefficient for which the on-state resistance of the drift layer is minimized. By doing so, this study allowed us to design the drift layer of doped diamond component in terms of doping level and thickness for a targeted breakdown voltage. Well known in silicon [8] and silicon carbide such a study has never been performed on diamond with realistic ionization coefficients. The optimized drift layer showed a Ron.S improvement up to 55% for a specified breakdown voltage. To avoid a pinch of the n-type channel layer a minimum dose is required. To evaluate it we took into account depleted area due to p-n junction formed with the p+ layer and to the p- drift layer connected respectively to the source and drain contacts. We also considered the minimum dose necessary to limit the potential increase in the channel in case of leakage current flowing between drain and back gate contacts. Such calculation emphasizes that high n-type doping level layer with important thickness should be grown to fulfill these requirements. Results presented in this work will allow proposing preliminary design rules to fabricate working and efficient unipolar diamond power devices. However we will show that thickness and doping (level and control) required for such structures are quite challenging for growth in the context of high voltage power devices. Indeed, these two parameters should be well controlled and particularly high and low doping level are necessary respectively for n-type channel and p-type drift layer.
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Dates et versions

hal-01288495 , version 1 (15-03-2016)

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  • HAL Id : hal-01288495 , version 1

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Gauthier Chicot, David Eon, Nicolas Clément, Jean-Paul Rouger. Optimal design of unipolar diamond power devices: drift region and channel dose. Hasselt Diamond Workshop 2016 - SBDD XXI, Mar 2016, Hasselt, Belgium. ⟨hal-01288495⟩
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