Relaxation characteristics of Ag(Ta,Nb)O/sub 3/ thin film varactors

Abstract

Silver tantalate niobate, which shows excellent microwave properties, was selected for this dielectric relaxation study. 4 /spl mu/m gap Au(500nm)/Cr(10nm)/Ag(Ta,Nb)O/sub 3/(0.4/spl mu/m) interdigital capacitors (IDC) fabricated on LaAlO/sub 3/ (LAO) and Al/sub 2/O/sub 3/ (sapphire) substrates were used as test structures. Frequency dispersion in the range 1 kHz to 1 MHz, loss tan/spl delta/, tunability and K-factor @ 100 kV/cm and 1 MHz were about 8.4%, 5.9%, 0.0033 and 17.8 and 3.5%, 3.8%, 0.0035 and 9.9 for IDCs on LAO and sapphire, respectively. Switching the voltage in stair-case mode results in slow and weak relaxation of the capacitance: at 50 kV/cm it was less than 0.05 % for 70 sec. Relaxation of leakage current follows power law: |I(t)/I/sub /spl infin//-1| = (t/12 s)/sup -0.98/.