  Motivated by recent experimental measurements of the tunneling
characteristics of high T_{c} materials using scanning tunneling spectroscopy,
we have calculated the IV and differential conductance curves in the
superconducting state at zero temperature. Comparing the two results obtained
via BCS-like d-wave pairing and the SU(2) slave boson approach, we find that
the slave-boson model can explain the asymmetric background observed in
experiments. The slave-boson model also predicts that the height of the
conductance peak relative to the background is proportional to the hole doping
concentration $x$, at least for under-doped samples. We also observe the
absence of the van Hove singularity, and comment on possible implications.
