Optical Power Efficiency Versus Breakdown Voltage of Avalanche-Mode Silicon LEDs in CMOS

Abstract

We report on the dependency of the optical power efficiency η on the breakdown voltage VBR of avalanche-mode (AM) light-emitting diodes (LEDs) in silicon. Lateral p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -n-n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> LEDs have been designed in a 65-nm bulk CMOS technology, where VBR is varied between 2 and 9 V. This tunes both the magnitude and the spatial distribution of the reverse electric field, which governs AM electroluminescence. Experiments show that a maximum η of ~1.7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> is obtained for V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> ~ 6 V. For V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> <; 6 V, non-local avalanche results in a lower η, while for V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> > 6 V, a gradual reduction in η with increasing VBR is obtained. This trend is compared with two recently proposed opto-electronic models. A maximum in η at relatively low voltages is attractive for monolithic opto-electronic integration in silicon.