Metallizations of InP based on transition metals

Abstract

Single element Ni and Cr metallizations to low doped n- and InP have been investigated to clarify how they affect electrical performance of advanced multilayer metallizations for ohmic contact and Schottky diode applications. It was found that the Ni and Cr contacts to n-InP show unstable ohmic behaviour at all annealing temperatures (300-500 °C), and that Ni and Cr metallizations to p-InP show diode behaviour. The electrical behaviour of the contacts were compared to phase formation paths of Ni-In-P and Cr-In-P ternary systems. From this it was found that amorphous ternary phases form first by interdiffusion of Cr and Ni into the InP crystal. Subsequently, at higher annealing temperatures, crystallization and eventually phase separation determines the electrical properties of the contacts. After annealing at 500 °C the Cr diodes to p-InP are almost ideal, as deduced from barrier height measurements using a combination of I-V and C-V methods. This indicates that the metallization forms a two-layer structure with Cr-P phases lying above pure In. The Ni diodes to p-InP annealed at 500 °C, on the other hand, are not ideal, indicating that Ni-In and Ni-(In)-P phases in parallel are determining the electrical properties of the diode.