Comparative study of homogeneously and inhomogeneously doped MIS coplanar transmission lines

A hybrid mode analysis is presented of slow-wave modes in microsize MIS CPWs (coplanar waveguides) on heavily doped thin- and thick-film semiconductor wafers, is presented. It was found that in homogeneously doped MIS CPWs, a slow-wave mode can be maintained up to 40 GHz if the center conductor strip width is on the order of 0.5 mu m. To circumvent fabrication and interconnection problems associated with such small line dimensions, a gradually inhomogeneous doping profile has been introduced, resulting in much wider strip dimensions in the range of 50 mu m. In this case, a slow-wave mode can be maintained up to 20 GHz. The study was carried out by using alternatively the spectral-domain approach and the method of lines. The method of lines is a very versatile numerical tool for analyzing transmission line cross sections of complicated shape.<>