Abstract
The ladder network (transmission line) technique for measuring the specific contact resistance of ohmic contacts to semiconductors is analysed, and the results of the analysis compared with the common approximations made in analysing experimental data. It is shown that the method fails when the transfer length and the width of the potential-measuring contacts are comparable. A graph is presented which allows corrections to be made as the measurement limit is approached, and a table gives the limiting values of specific contact resistance that can be measured for specific ladder geometries and semiconductor sheet resistivities. The 'variable gap' structure is shown to be free of the limitations of the ladder network because it has no narrow, potential-measuring electrodes. Experimental data for gold-germanium contacts to gallium arsenide are given to illustrate the above results.