CHARACTERIZATION OF BST BASED VARACTOR FOR PHASE SHIFTER APPLICATION

Abstract

The work presented here is on pure BST and Mg doped BST thin film. Fabrication of planer capacitor was done using sol-gel based spin coating technique on substrate of n-type Si (IOU). Uniformly composed and well-developed dense crystalline structure with uniform distribution of grain size were successfully produced. The main purpose of this work is to enhance the tunability as compared to conventional thin film materials while retaining the high voltage bias capability and higher phase shift at microwave frequencies. The C —V characterization were studied for fabrication and design of BST varactor phase shilier. The BST thin films showed good dielectric properties. The phase shifter device based on coupled micrOstrip line structure was fabricated and design. The 13aSriTiO3 (x=0.5) thin films had paraelectric nature and loss tangent values at zero bias and f= 1 MHz were found to be 0.7 and 0.32 for undoped Mg doped BST film respectively. The leakage current density at 40 kV/cm was found to be .08A/cm2in case of undoped BST and 0.0005A/cm2 for BST films doped with Mg. it was found that C-V curve showed nonlinear dependence on applied field, thickness and annealed temperature. The 1unabi1ity30% and 42% were found for pure and BST films doped with Mg respectively. I lowever the phase shill of —390 for BST and —34° for the Mg doped BST were observed at 2.9G1-lz.