Increased efficiency of silicon light-emitting diodes in a standard 1.2-μm silicon complementary metal oxide semiconductor technology

Scaled versions of a variety of silicon light-emitting diode elements (Si LEDs) have been realized using a standard 1.2-μm, double-polysilicon, double-metal, n-well CMOS fabrication process. The devices operated with a n⁺p junction biased in the avalanche breakdown mode and were realized by using standard features of the ORBIT FORESIGHT design rules. The elements emit optical radiation in a broad band in the 450- to 850-nm range. An emitted intensity (radiant exitance) of up to 7.1 μW/cm² (or about 8 nW per 60-μm-diam chip area) has been obtained with 5 mA of current at an operating voltage of 18.5 V. Excellent uniformity in emission intensity of better than 1% variation was obtained over areas as large as 100×500 μm. A best power conversion efficiency of 8.7×10^-8 and a quantum efficiency of 7.8×10^-7 were measured All of these values are about one order of magnitude better than previously reported values for Si LED avalanche devices. Coupling between the elements as well as electro-optical coupling between an element and an optical fiber was realized.