A GaN-based metal-semiconductor-metal planar inter-digitated varactor

In this paper, a GaN-based metal-semiconductor-metal planar inter-digitated varactor is analyzed. The quality factor of the inter-digitated varactor with finger width of 0.25μm and space between fingers of 7μm on sapphire is 31.9 at 100MHz, and the tunable capacitance ranges fro m 0.19pF to 0.89pF. The characteristics of this varactor with different finger's widths and spaces are analyzed. It is shown that the maximum capacitance depends on the total area of fingers and the minimum capacitance lies on fingers' width and the space between fingers. When either width or space is fixed, the minimum capacitance decreases with the increase of the other one.