Method for measuring contact resistivity

Abstract

Abstract It is well known that high contact resistivity is detrimental to the performance of solar cells. Cadmium telluride (CdTe), frequently used for solar cells, have low doping levels which results in high contact resistivities and, consequently, in poor ohmic contacts. Most of the methods in use for measuring the contact resistivity of other semiconductors, such as Si or GaAs, are designed with a high doping density in mind. These high doping densities are currently not achievable in CdTe and, terefore, the measurement of contact resistivity on CdTe with these methods is not possible or can at the best yield erroneous results. A method for measuring the contact resistivity has been developed to be accurate in the required bulk resistivity range for CdTe which is usually a few order of magnitude higher than that of Si and GaAs. This method takes into account the geometry of the contacts in the spreading resistance, and the bulk resistance of the semiconductor between two contacts that are manufactured on the same side of a CdTe sample. Results using this method for measuring the contact resistivity of In ohmic contacts on n-type CdTe will be presented.