Single element Ni and Cr metallizations to low doped n- and p-Inl have
been investigated to clarify how they affect electrical performance o
f advanced multilayer metallizations for ohmic contact and Schottky di
ode applications. It was found that the Ni and Cr contacts to n-InP sh
ow unstable ohmic behaviour at all annealing temperatures (300-500 deg
rees C), and that Ni and Cr metallizations to p-InP show diode behavio
ur. The electrical behaviour of the contacts were compared to phase fo
rmation 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 C
r and Ni into the InP crystal. Subsequently, at higher annealing tempe
ratures, crystallization and eventually phase separation determines th
e electrical properties of the contacts. After annealing at 500 degree
s C the Cr diodes to p-InP are almost ideal, as deduced from barrier h
eight measurements using a combination of I-V and C-V methods. This in
dicates that the metallization forms a two-layer structure with Cr-P p
hases lying above pure In. The Ni diodes to p-InP annealed at 500 degr
ees 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.