We have probed the luminescence properties of a wide-band-gap, direct band-gap optoelectronic material, grown on closely lattice-matched silicon substrates, namely, gamma-CuCl on Si. This material system is compatible with current Si or GaAs-based electronic/optoelectronic technologies. Polycrystalline epitaxy of CuCl can be controlled such that it maintains an orientation similar to the underlying Si substrate. Importantly, chemical interactions between CuCl and Si are eliminated. Photoluminescence and cathodoluminescence results for CuCl, deposited on either Si (100) or Si (111), reveal a strong room-temperature Z(3) excitonic emission at similar to 387 nm. We have developed and demonstrated the room-temperature operation of an ultraviolet electroluminescent device fabricated by the growth of gamma-CuCl on Si. The application of an electrical potential difference across the device results in an electric field, which promotes light emission through hot-electron impact excitation of electron-hole pairs in the gamma-CuCl. Since the excitonic binding energy in this direct band-gap material is of the order of 190 meV at room temperature, the electron-hole recombination and subsequent light emission at similar to 380 and similar to 387 nm are mediated by excitonic effects. (c) 2005 American Institute of Physics.