Abstract: An electroluminescent silicon device comprises a light emitting diode (10). The diode (10) includes a p.sup.+ semiconductor contact (42) and a n.sup.- layer (32), forming a p-n junction (43) therebetween. The n.sup.- layer (32) is carbon-doped and irradiated with an electron beam having electrons with energies of between 150 and 400 keV to form G-centres. The diode (10) is electroluminescent when forward biassed, radiative recombination occuring at the G-centres. The invention reconciles the conflicting requirements of creating luminescent defect centres by irradiation while avoiding damage to electronic properties. The device may be an integrated light emitting diode (200) incorporated in a CMOS microcircuit. Photon output from the diode (200) may be relayed to other parts of a CMOS microcircuit by an integrated waveguide (224).