The achievement of efficient room-temperature light emission from crystalline Si is a crucial step toward the achievement of fully Si-based optoelec-tronics. However Si, the leading semiconductor in microelectronic applications, is unable to perform as well in the optical arena. In fact due to its indirect bandgap, Si does not exhibit efficient light emission and has been considered unsuitable for optoelectronic applications. Several efforts have been dedicated to overcoming this limitation. Among them, luminescence through the incorporation of rare-earth impurities has been considered In particular, erbium doping has been demonstrated as a valid approach toward achievement of efficient light emission from Si.1−43 Erbium is a rare-earth ion that, in its 3+ state, can emit photons at 1.54 μm because of an intra-4f shell transition between the first excited state (4I13/2) and the ground state (4I15/2). This emission is particularly attractive because its wavelength falls inside a window of maximum transmission for the silica optical fibers. When Er ions are inserted within a Si matrix, the excitation (4I15/2 → 4I13/2) can be achieved through the carriers provided by the host, whereas the subsequent deexcitation (4I13/2 → 4I15/2) can result in a sharp, atomlike light emission.