Thermally Stable Operation of H-Terminated Diamond FETs by $\hbox{NO}_{2}$ Adsorption and $\hbox{Al}_{2}\hbox{O}_{3}$ Passivation

Using the NO
₂
adsorption and Al
₂
O
₃
passivation technique, we improved the thermal stability of hydrogen-terminated diamond field-effect transistors (FETs) and then demonstrated stable operation at 200 °C in a vacuum for the first time. At 200 °C, the drain current I
_DS
of a passivated diamond FET remained constant for at least more than 2 h. No degradation of FET characteristics was observed after the 200 °C heating cycle. Furthermore, a passivated diamond FET with a gate length of 0.2 μm showed high maximum I
_DS
of -1000 mA/mm and an RF output power density of 2 W/mm.