TI/PT/AU OHMIC CONTACTS TO N-TYPE ZNSE

We report that a Ti/Pt/Au multilayered metal structure can make a nonalloy ohmic contact to n-type ZnSe with an electron concentration greater than 10(19) cm-3. A specific contact resistance as low as 3.4 x 10(-4) OMEGA-cm2 was achieved for Cl-doped ZnSe with an electron concentration of 2 X 10(19) cm-3. We think that the lower contact resistance can be ascribed to the higher reactivity and adhesion of Ti metal with the surface of ZnSe at low temperature, and to the lower work function of Ti metal. The dominant current flow may be due to the quantum mechanical tunneling of electrons through the potential barrier at the ZnSe surface, because the specific contact resistance decreases with an increase in the electron concentration. A small improvement in the specific contact resistance was made by thermal annealing at a temperature of 250-degrees-C for 5 min, which yielded the lowest value of 1.1 X 10(-14) OMEGA-cm2. With annealing at 300-degrees-C and below, the contact resistance was not drastically increased. The electrical properties of the contact are therefore thermally stable up to 300-degrees-C.