Nonlinear I-V in semiconductor

I used a compound semiconductor and a metal layer wishing to form a
schottky barrier, but when I measured its I-V characteristics, it
showed a diode-like behavior in either direction of current. The
curves are exactly same in either polarity of the applied voltage. I
think if a shottky junction was formed, it would not be the case. What
is happening in my device? Any suggestion is appreciated.