ALLOWING FOR CURRENT SPREADING IN SEMICONDUCTORS DURING MEASUREMENTS OF THE CONTACT RESISTIVITY OF OHMIC CONTACTS

A modification of the contact-area pattern with radial geometry, which has certain advantages in determining the contact resistivity of ohmi c contacts (rho(c)) fabricated on substrates and low-resistance semico nductor layers, is proposed. Different variants of its application for both the transmission line method (TLM) and methods based on a numeri cal calculation of the resistance of the semiconductor with allowance for current spreading are considered. It is shown that the transmissio n line method makes it possible to obtain an upper estimate of the con tact resistivity on substrates. The errors of such estimates are also calculated as a function of the parameters of the semiconductor and th e contact. The TLM estimate is a good first approximation for determin ing the exact value of rho(c) by numerically calculating the resistanc e of the semiconductor. The results obtained are used to study the con tact resistivity of Ni-based ohmic contacts on n-6H-SiC substrates. (C ) 1998 American Institute of Physics.