Ferroelectric Varactor on Diamond for Elevated Power Microwave Applications

A ferroelectric (FE) varactor with a film structure Ba
_x
Sr
_1-x
TiO
₃
(BSTO)/SiC on a diamond substrate, designed for the use under elevated microwave (MW) power, was produced by an ion-plasma deposition technique. Comparative testing of the BSTO varactors produced on Al
₂
O
₃
and diamond/SiC substrates was performed at the frequency of 3 GHz and different levels of MW power (up to P ~ 10 var). A significant difference in thermal response under MW power of the varactors on Al
₂
O
₃
and diamond was demonstrated: the overheating of FE film was observed as AT ~ (20-30) K on Al
₂
O
₃
and ΔT ~ 2 K on diamond at maximum MW power.