Designer germanium quantum dot phototransistor for near infrared optical detection and amplification

We demonstrated a novel CMOS approach for the fabrication of high-performance germanium quantum dot (QD) phototransistor (PT) offering great promises as optical switches and transducers for Si-based optical interconnects. Illumination produces significant enhancement in the drain current of Ge QD PTs when biased at both on-and off-states, primarily resulting from photoconductive and photovoltaic effects. Measured photocurrent to dark current ratio (I_ph/I_dark) and photoresponsivities from the Ge QD PT were as high as 53,000 and 2.7 A/W, respectively, under incident power of 0.9mW at 850 nm illumination.