International audienceMetal-oxide-semiconductor structures with aluminum oxide as insulator and p-type (100) mono-crystalline diamond as semiconductor have been fabricated and investigated by capacitance versus voltage and current versus voltage measurements. The aluminum oxide dielectric was deposited using low temperature atomic layer deposition on an oxygenated diamond surface. The capacitance voltage measurements demonstrate that accumulation, depletion, and deep depletion regimes can be controlled by the bias voltage, opening the route for diamond metal-oxide-semiconductor field effect transistor. A band diagram is proposed and discussed

International audienceDiamond metal-oxide-semiconductor capacitors were prepared using atomic layer deposition at 250 °C of Al2O3 on oxygen-terminated boron doped (001) diamond. Their electrical properties were investigated in terms of capacitance and current versus voltage measurements. Performing X-ray photoelectron spectroscopy based on the measured core level energies and valence band maxima, the interfacial energy band diagram configuration of the Al2O3/O-diamond is established. The band diagram alignment is concluded to be of type I with valence band offset ΔEvΔEv of 1.34 ± 0.2 eV and conduction band offset ΔEcΔEc of 0.56 ± 0.2 eV considering an Al2O3 energy band gap of 7.4 eV. The agreement with electrical measurement and the ability to perform a MOS transistor are discussed

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Metal oxide semiconductor capacitors were fabricated using p-type oxygen-terminated (001) diamond and Al2O3 deposited by atomic layer deposition at two different temperatures 250 °C and 380 °C. Current voltage I(V), capacitance voltage C(V), and capacitance frequency C(f) measurements were performed and analyzed for frequencies ranging from 1 Hz to 1 MHz and temperatures from 160 K to 360 K. A complete model for the Metal-Oxide-Semiconductor Capacitors electrostatics, leakage current mechanisms through the oxide into the semiconductor and small a.c. signal equivalent circuit of the device is proposed and discussed. Interface states densities are then evaluated in the range of 1012eV−1cm−2. The strong Fermi level pinning is demonstrated to be induced by the combined effects of the leakage current through the oxide and the presence of diamond/oxide interface states.

Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO 2 deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprised of a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on a Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that of R.T. Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones, (b) annealed at 350℃, (c) annealed at 450℃ with characteristic barrier heights of 2.2-2.5 V in case (a) while as low as 0.96 V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces.

Owing to its outstanding electro-thermal properties, such as the highest thermal conductivity (22 W/(cm∙K) at room temperature), high hole mobility (2000 cm2/(V∙s)), high critical electric field (10 MV/cm) and large band gap (5.5 eV), diamond represents the ultimate semiconductor for high power and high temperature power applications. Diamond Schottky barrier diodes are good candidates for short-term implementation in power converters due to their relative maturity. Nonetheless, diamond as a semiconductor for power devices leads to specificities such as incomplete dopant ionization at room temperature and above, and the limited availability of implantation techniques. This article presents such specificities and their impacts on the optimal design of diamond Schottky barrier diodes. First, the tradeoff between ON-state and OFF-state is discussed based on 1D analytical models. Then, 2D numerical studies show the optimal design of floating metal rings to improve the effective breakdown voltage. Both analyses show that the doping of the drift region must be reduced to reduce leakage currents and to increase edge termination efficiency, leading to better figures of merit. The obtained improvements in breakdown voltage are compared with fabrication challenges and the impacts on forward voltage drop.

This paper proposes a system-level comparison between diamond and SiC power devices. It highlights the benefits of diamond semiconductors for power electronics applications. Actual diamond power devices are fabricated and characterized (DC, AC small-signal and largesignal power switching in a buck converter). Thanks to the experimental data, the models of diamond devices are discussed and the expected performances of future diamond semiconductors in power converters are presented. These performances are compared to the commercialized SiC Schottky diodes for a given application. Our analysis shows that diamond devices can be used to increase power converters' performances especially at high temperature. It is demonstrated that for a 450K junction temperature diamond semiconductors can divide by three the semiconductor losses and heatsink volume in comparison to SiC devices. We also demonstrate that the switching frequency with diamond devices can be five times higher than with SiC devices, with lower total semiconductor losses and smaller heatsink in diamond based power converters. This system level analysis clearly shows the future improvements of power converters' efficiency and their power densities thanks to diamond power devices. The need of a

We report the 250 • C operation of a diamond-based monolithic bidirectional switch. A normally-ON double gate deep depletion MOSFET was fabricated with a 400 nm p-type channel with a boron doping of [N AN D ]= 2.3×10 17 cm −3 and an Al 2 O 3 gate oxide thickness of 50 nm. The I st and III rd quadrants transistor characteristics are successfully measured by controlling the channel conductivity with both gates separately, with a clear ON and OFF state. A threshold voltage around 35 V is obtained with a low minimum gate leakage current of 1.00 × 10 −4 mA/mm at a gate-source bias V GS = 50 V. The bidirectional switch is then obtained by operating the MOSFET in the I st quadrant of each gate setup. This first proof of concept offers a reverse conducting and reverse blocking diamond MOSFET, with only one drift region layer.