A 20 GHz MOD-made BST thin film tunable phase shifter for phase adjustment of digital 360-degree PHEMT phase shifter

We have newly designed and fabricated both BaxSr1-xTiO3 (BST) ferroelectric thin film tunable phase shifter and pseudomorphic HEMT MMIC digital 360-degree phase shifter. A low loss BST thin film was obtained on MgO substrate by preparation of initial layer by Pulsed Laser Deposition (PLD) and following Metal-Organic-Decomposition (MOD) method. For the interdigital capacitors with finger spacing of 10 µm, dielectric loss was found to be as low as 0.002 to 0.004 when applied surface electric field was from -/+40 to +/-40 kV/cm at measuring frequency of 1 MHz, where tunability was about 12%. Moreover, it increases up to about 40 % in a Pt/BST/Pt stacked capacitor structure when the applied electric field was from -/+170 to +/- 170 kV/cm at the same frequency.