GAAS TUNNETT DIODES ON DIAMOND HEAT SINKS FOR 100-GHZ AND ABOVE

Single-drift GaAs TUNNETT diodes were mounted on diamond heat sinks fo r improved thermal resistance and evaluated around 100 GHz in a radial line full height waveguide cavity. The diodes mere fabricated from MB E-grown material originally designed for diodes that operate in CW mod e around 100 GHz on integral heat sinks. An RF output power of more th an 70 mW with a corresponding de to RF conversion efficiency of 4.9% w as obtained at 105.4 GHz., This is the first successful demonstration of GaAs TUNNETT diodes mounted on diamond heat sinks. To the authors' knowledge, these de to RF conversion efficiencies and RF power levels are the highest reported to date from TUNNETT diodes and exceed those of any single discrete device made of group III-V materials (GaAs, InP , etc.) at this frequency. Free-running TUNNETT diode oscillators exhi bit clean spectra with an excellent phase noise of less than -94 dBc/H z, measured at a frequency off-carrier of 500 kHz and an RF output pow er of 40 mW.