EXTREMELY LOW CONTACT RESISTIVITY OF TI/PT/AU CONTACTS ON P+-INGAAS AS DETERMINED BY A NEW EVALUATION METHOD

A convenient method for determining a low contact resistivity rho(c) is described and experimental results are presented. Small dots of p+-InGaAs on a thick and highly conductive substrate are metallized. The corresponding boundary problem of the current distribution is solved by using an integral equation which can be evaluated numerically. This method can be used to obtain rho(c) from experimental data. The procedure overcomes the difficulties usually encountered with the transmission line method since the inhomogeneity of the current density under the contact dots is fully taken into account. The exact knowledge of the diameter of the dots is imperative and must be examined using a scanning electron microscope. The p-In0.53Ga0.47As contact layer which is placed on a p-InP substrate (p = 6 . 10(18) cm-3) is heavily p+-doped (2 . 10(20) CM-3) using a zirconia-based diffusion source. Lowest rho(c) values obtained are smaller than 1 . 10(-6) OMEGA cm2, which are among the best for p-contacts ever reported.