We have fabricated the Au/SiO2/Si Metal/Insulator/Semiconductor tunnel junctions (MISJ) using heavily Sb-doped Si wafers and an SiO2 insulating layer. Stable, uniform, broadband (500-900 nm) light emission was observed from the MISJ with an emission efficiency of 10(-5) which is one to two orders of magnitude higher than that of an Au/Al2O3/Al junction. The light emission spectrum has main peaks at 620 (2.00 eV) and 735 nm (1.69 eV). A negative resistance phenomenon (NRP) in the I-V curve, possibly due to surface plasmon polariton (SPP) scattering on the tunneling electrons, is closely associated with Light emission. The MISJ is compatible with Si microelectronic technology and can be used for new kinds of integrated optoelectronic and photonic devices.