Diamond RF Transistor Technology with f t =41 GHz and fmax=44 GHz

Initial results for diamond RF transistor technology are presented. Field Effect Transistors (FETs) were fabricated with gate lengths $(mathbf{L}_{mathrm{g}})$ ranging from $mathbf{4}pmb{mu}mathbf{m}$ to 50nm. The FETs have total gate width $(mathbf{W}_{mathrm{g}})$ of 40 or $mathbf{120}pmb{mu}mathbf{m}. mathbf{L}_{mathbf{g}}=mathbf{100 nm}$ devices show DC drain current $mathbf{I}_{mathbf{D}}=mathbf{600 mA}/mathbf{mm} (u003emathbf{V}_{mathbf{GS}}=-mathbf{3V},mathbf{V}_{mathbf{DS}}=-mathbf{10V}$ ) with transconductance $mathbf{g}_{mathbf{m}}=mathbf{140mS}/mathbf{mm} (u003emathbf{V}_{mathbf{GS}}=-mathbf{0.3V},mathbf{V}_{mathbf{DS}}=-mathbf{4V}$ ). Small signal S-parameters were measured to evaluate the high-frequency performance of the diamond FETs. Extrinsic $mathbf{f}_{mathbf{t}}$ and $mathbf{f}_{mathbf{max}}$ were measured to be 41GHz and 44GHz, respectively. Load pull measurements were used to characterize the devices under large signal excitation. The $mathbf{L}_{mathbf{g}}=mathbf{200nm}, mathbf{W}_{mathbf{g}}=mathbf{40}pmb{mu}mathbf{m}$ device, tested at 2GHz, shows peak efficiency of 30.5% at $mathbf{V}_{mathbf{DS}}=-mathbf{5V}$ . Both peak gain of 19.5dB and peak output power density of 0.66W/mm were achieved at $mathbf{V}_{mathbf{DS}}=- mathbf{30V}$ , Biasing the device at $mathbf{V}_{mathbf{DS}}=-mathbf{15V}$ provides a trade off point for the large signal parameters - gain of ~15dB, efficiency of ~20%, and output power of ~0.5W/mm.