  Graphene interfaced with a semiconductor forms a Schottky junction with
rectifying properties, however, fluctuations in the Schottky barrier height are
often observed. In this work, Schottky junctions are fabricated by transferring
chemical vapor deposited monolayer graphene onto n-type Si and GaAs substrates.
Temperature dependence of the barrier height and ideality factor are obtained
by current-voltage measurements between 215 and 350 K. An increase in the zero
bias barrier height and decrease in the ideality factor are observed with
increasing temperature for both junctions. Such behavior is attributed to
barrier inhomogeneities that arise from interfacial states as revealed by
scanning tunneling microscopy/spectroscopy. Assuming a Gaussian distribution of
the barrier heights, mean values of 1.14(+/-)0.14 eV and 0.76(+/-)0.10 eV are
found for graphene Si and GaAs junctions, respectively. These findings provide
insights into the barrier height inhomogeneities in graphene based Schottky
junctions, essential for the integration of graphene with Si and GaAs device
architectures.
