Diamond RF Research Articles

H-terminated diamond RF MOSFETs with AlOx/SiNx bi-layer passivation and selectively etched T-shaped gates

This paper reports a novel ALD-AlOx/PECVD-SiNx bi-layer structure to passivate the surface channels of the hydrogen terminated diamond transistors. The upper SiNx was selectively etched to fabricate the robust T-shaped gates, while the lower thin AlOx with high quality was retained as the gate insulator. The fabricated device with gate length of 0.3 μm demonstrated a high current density of 715 mA/mm, a low on-resistance of 8 Ω·mm, and an extrinsic fT/fmax of 10/20 GHz. RF power output characteristics were investigated at 2 GHz and a maximum output power density of 703 mW/mm was obtained at a low drain voltage of −15 V. It reveals that it is a promising solution for high stable and high power diamond RF transistors and microwave integrated circuits by using the AlOx/SiNx passivation structure.

A fiber based diamond RF B-field sensor and characterization of a small helical antenna

We present a microwave B-field scanning imaging technique using a diamond micro-crystal containing a nitrogen vacancy center that is attached to a fiber tip. We propose a pulsed modulation technique, enabling the implementation of a variety of pulsed quantum algorithms for state manipulation and fast readout of the spin state. A detailed mapping of the magnetic B-field distribution of a helical antenna with sub-100 μm resolution is presented and compared with numerical simulations. This fiber based microwave B-field probe has the advantages of minimized invasiveness and small overall size and will boost broad interest in a variety of applications where near field distribution is essential to device characterization, to name a few, antenna radiation profiling, monolithic microwave integrated circuit failure diagnosis, electromagnetic compatibility test of microwave integrated circuits, and microwave cavity field mode mapping.

Diamond RF FETs and other approaches to electronics

AbstractDiamond semiconductor possesses exceptional physical properties, such as high thermal conductivity, high breakdown field, and high mobility, and is therefore expected to offer the highest performance among semiconductors as high‐frequency, high‐power transistors. At present the most critical issue in achieving diamond transistors is the lack of an n‐type or p‐type dopant with low activation energy. This paper reviews approaches towards electronic‐device application of diamond done mainly by NTT Basic Research Laboratories. First it describes our diamond field‐effect transistors with 0.1‐μm gate length, which exhibit high cut‐off frequencies for the current and power gains, fT and fMAX, of 45 GHz and of 120 GHz, and output power density of 2.1 W/mm at 1 GHz. Next it shows how doping efficiency in ion implantation can be improved by using high‐pressure high‐temperature annealing. Finally, it describes our concept of diamond/nitride heterostructure and presents results that confirm its feasibility. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Performance of amorphous diamond RF MEMS capacitive switch

Radio frequency microelectromechanical systems (RF MEMS) capacitive switches using amorphous diamond (a-D) as a novel dielectric with controlled leakage have been successfully developed. The devices show a unipolar switching response to a unipolar stimulus, indicating the absence of significant dielectric charging. These initial devices exhibit a down-state capacitance of 2.6 pF and a predicted static power dissipation of 10 nW. This technology is promising for the development of reliable, low-power RF MEMS switches.

The development of a diamond switch for RF pulse compression systems

The use of a diamond RF switch for super-highpower microwave/millimeter wave generation has been evaluated. An X-band chemical vapor deposition (CVD) diamond window package was theoretically analyzed, designed, and built. Thirty-eight percent of an injected microwave signal with a frequency of 11.424 GHz was reflected from a 100-/spl mu/m thick, 22-mm-diameter CVD diamond window when activated by a 160-mJ, 266-nm Nd:YAG laser. The details of the CVD diamond window design and experimental results are presented. The results have high application potential for building super-high-power microwave systems.