Accelerated stressing and degradation mechanisms for Si-based photoemitters

A silicon p-n junction biased in avalanche breakdown mode emits visible light. Such a diode offers the potential for very large scale integration (VLSI)-compatible light emitters for on/off chip signal transmission and contactless functional testing of wafers. The reliability of such emitters must be evaluated before widespread use is possible. Si light emitters were stressed with ac excitation, dc excitation, and increased temperature to accelerate the aging. The results clearly show that the effects of ac and temperature stressing are negligible on light emission. DC stressing results in light coalescence for low values of current (less than 25 mA) with total light emission coming out of the junction remaining constant. However, dc stressing with large current values (larger than 40 mA) does not show light coalescence. The light coalescence phenomenon can be reversed when emitters are subjected to higher levels of currents. The difference in light coalescence behavior for large and small values of dc excitation and the reversibility of the phenomenon is consistent with the hydrogen migration model.