Gennaro Conte

Very Fast and Primingless Single-Crystal-Diamond X-Ray Dosimeters

X-ray dosimeters were developed by tailoring novel injecting diamond-like-carbon/Pt/Au contacts on single-crystal high-purity diamond films. A dark resistivity of (5.6 ± 0.1) × 10¹⁴ Ω · cm and no appreciable presence of deep traps in the bandgap confirmed a very low defect density in the diamond films. The dosimeters resulted to be primingless (i.e., no need of preactivation) and characterized by high sensitivity [(58.20 ± 3.26) × 10^-3 C · Gy^-1 cm^-3] and linear response to X-ray dose rate, produced by a molybdenum target. Transient X-ray modulated analysis allowed the determination of fast-trap influence and the estimation of very fast response times (~10^-3 s), at electric fields ≥ 3 × 10³ V/cm.

Opaque-Gate Phototransistors on H-Terminated Diamond

Opaque-gate ultraviolet sensitive transistors were fabricated on H-terminated polycrystalline diamond. Butterfly shaped structures with different geometric ratios were realized. Observed trends with the gate unbiased demonstrated behavior as p-channel normally-off transistors, switched-on by the impinging UV light. Linearity with the UV beam power was also observed with over-gap radiation. Under steady state illumination, a linear increase of the photocurrent was found when the gate is biased at different voltages in the saturation regime. The operative generation-charge transport mechanism of fabricated devices is discussed.

Microwave performance of surface channel diamond MESFETs

Sub-micron gate length Metal Semiconductor Field Effect Transistors (MESFETs) have been realized on polycrystalline diamond samples supplied by Element Six Ltd. and by Russian Academy of Science. RF performances are shown for devices realized on polycrystalline diamond samples of different quality, stating the successfully improvement and reliability of realization technology.

Modeling of Metal-Semiconductor Field-Effect-Transistor on H- terminated polycrystalline diamond

On the bases of the RF characteristics and measured small-signal parameters, an equivalent circuit model is formulated and characterized for Metal-Semiconductor Field Effect Transistors based on H-terminated polycrystalline diamond. Starting from on-wafer measurements, a bias dependent transistor behavior representation has been fully determinated. Such a equivalent circuit model is a first important step in order to realize an RF IC based on diamond.

MESFETs on H-terminated Single Crystal Diamond

Epitaxial diamond films were deposited on polished single crystal Ib type HPHT diamond plates of (100) orientation by microwave CVD. The epilayers were used for the fabrication of surface channel MESFET structures having sub-micrometer gate length in the range 200-800 nm. Realized devices show maximum drain current and trasconductance values of about 190 mA/mm and 80 mS/mm, respectively, for MESFETs having 200 nm gate length. RF performance evaluation gave cut off frequency of about 14 GHz and maximum oscillation frequency of more than 26 GHz for the same device geometry.