DIRECT EVIDENCE OF IMPACT EXCITATION AND SPATIAL PROFILING OF EXCITEDER IN LIGHT-EMITTING SI DIODES

We provide direct evidence that Er ions incorporated in the depletion layer of a p(+)-n(+) Si junction are efficiently pumped through an imp act excitation process with hot carriers. The carriers were accelerate d by the electric field present in the depletion layer after being pro duced by either Zener breakdown of the junction at similar to 5 V or b y irradiating the diode with an argon laser. Measurements of the elect roluminescence yield at 1.54 mu m as a function of the reverse bias vo ltage (and for a constant current through the device) reveal that exci tation of Er only occurs at voltages above 1 V, demonstrating that imp act is the pumping mechanism. Moreover, we have found that Er ions are only excited within similar to 15 nm from the edges of the depletion layer leaving a dark, similar to 50 nm thick, region in the central pa rt of the depletion region. Monte Carlo calculations confirmed that on ly close to the depletion layer edges the energy gained by the carrier s in the electric held is high enough to impact excite Er. (C) 1998 Am erican Institute of Physics.