This work investigates electrical properties of contacts between undoped solid C60 and n-or p-type Si. Current-voltage measurements show that the two contacts result in strong rectification with opposite conduction directions, indicating two different kinds of barriers for carrier transportation at the interface of the two contacts. Current-temperature measurements show that the current is an exponential function of reciprocal temperature, from which we estimate the effective barrier height to be 0.30 and 0.48 eV for C60/n-Si and C60/p-Si, respectively. Within energy-band models we interpret successfully the above experimental results. Based on the energy-band model and experimental data we derived the electron affinity of solid C60 film to be 3.92 eV and its energy gap to be below 1.72 eV. Highfrequency capacitance-voltage measurements show that biastemperature treatments have considerable effect on the C-V characteristics of the heterojunction. Assuming the existence of mobile negative charges in the solid C60 film we explain the effect successfully and estimate the density of the negative charges to be 3.1×1012cm-2. By use of the C-V results we determine the dielectric constant of the solid C60 film to be 3.7±0.1 in the temperature range of 300-370 K.