Diamond Fet Using High-Quality Polycrystalline Diamond Wafer With Ft of 45 GHz and fmax of 120 GHz

Using high-quality polycrystalline chemical-vapor-deposited diamond films with large grains (/spl sim/100 μm), field effect transistors (FETs) with gate lengths of 0.1 μm were fabricated. From the RF characteristics, the maximum transition frequency f T and the maximum frequency of oscillation f max were /spl sim/ 45 and /spl sim/ 120 GHz, respectively. The f T and f max values are much higher than the highest values for single-crystalline diamond FETs. The dc characteristics of the FET showed a drain-current density I/sub DS/ of 550 mA/mm at gate-source voltage V/sub GS/ of -3.5 V and a maximum transconductance g/sub m/ of 143 mS/mm at drain voltage V/sub DS/ of -8 V. These results indicate that the high-quality polycrystalline diamond film, whose maximum size is 4 in at present, is a most promising substrate for diamond electronic devices.

Diamond is expected to be the most suitable material for high-power high-frequency electronic devices because of its high electric breakdown field ( 10 MV/cm), high carrier mobility (4500 for electrons, 3800 for holes), high thermal conductivity (22 ), and high saturation velocity ( for electrons, for holes). Recently, using a single-crystal chemical-vapor-deposited (CVD) diamond, we achieved a maximum output power density of 2.1 W/mm at 1 GHz, which is the highest reported among diamond FETs. This output power density is high enough for power amplifiers of base stations in wireless communication systems.

CSMH focuses on the R&D and production of diamond wafers, and has created an efficient and precise machining method for diamond atomic-level surfaces based on plasma-assisted polishing, diamond wafer Ra<1nm, diamond heat sink thermal conductivity 1000-2000W/m.k, and GaN on diamond, Diamond on GaN, diamond-based aluminum nitride and other products. We will keep pursuing the innovation-driven development strategy in the future, offering our customers products of high quality and reliable performance while contributing the rapid development of the global semiconductor industry.