Mean-gain and excess-noise measurements are presented for a 350 × 350 μm2 P+/N-well/P-sub and a 270 × 270 μm2 N-well/P-sub avalanche photodetectors fabricated using 0.13-μm CMOS technology. The active area of the P+/N-well/P-sub device was divided into multiple subsections to decrease transit time and increase speed. For the P+/N-well structure, remarkably low excess-noise factors of 4.1 and 4 were measured at a mean gain of 16 corresponding to a k value of approximately 0.1, using a 542 (633) nm laser. For a variant N-well/P-sub structure, excess-noise factors of 6.5 and 6.2 were measured at a mean-gain of 16 corresponding to a k value of approximately 0.3. The proposed CMOS APDs with high gain, low noise, low avalanche breakdown voltage (below approximately 12 V) and low dark-currents (approximately nA) would be attractive for low-cost optical receivers in visible-light communication systems.
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