ION-IMPLANTATION DOPING OF SI FOR OPTOELECTRONIC APPLICATIONS

We show that the major problems hampering efficient performances of Si in optoelectronic applications, i.e. the achievement of efficient lig ht emission and fast modulation, can be successfully approached by a p roper engineering of its optical properties. In particular, the incorp oration of a high Er concentration, if concomitant with codoping with other impurities such as O and F, allows to achieve efficient 1.54 mu m light emission at room temperature. This emission arises from an ele ctrically excitable, atomically sharp, intra 4f transition of the Er i ons. The formation of impurity-rare earth ion complexes is shown to en hance the effective solubility of Er in Si and optimize its electrical properties thus providing a higher excitation efficiency and a reduct ion of the temperature quenching of the luminescence yield. Furthermor e we show that the proper design of a Si light emitting diode, allowin g the incorporation of Er ions within the depletion layer region of a p(+)-n(+) junction, allows to achieve simultaneously high efficiency a nd fast modulation of the electroluminescence signal. In fact, under r everse bias, Er ions are pumped with a cross section of 6 x 10(-17) cm (2) and decay with a lifetime of 100 mu s, which guarantees an interna l quantum efficiency > 10(-4) and an emitted power of similar to 30 mu W at room temperature. On the other hand, at the diode turn-off, the onset of fast, non-radiative, Auger-type decay processes of the excite d ions allow a very fast turn off of the electroluminescence signal.