Zero-Process-Change SiGe Heterojunction Avalanche Photodiode for High-Speed, High-Gain Detection Near the Silicon Band Edge

A novel design for a silicon-integrated avalanche photodiode (APD) capable of high internal gain (>16,000) is presented. The APD was fabricated in an unmodified, commercial high-volume, high-performance (300 GHz f
_T
/f
_MAX
) silicon-germanium (SiGe) BiCMOS technology. The APD's high gain is partially attributed to the enhanced lateral carrier mobility of its strained SiGe anode, and the low sheet resistance of its cathode contact. These design aspects lower parasitic resistance and improve junction electric field uniformity, increasing maximum gain. For applications not requiring maximum device speed, a time-resolved overall responsivity of 4.2 A/W is demonstrated, with a photocurrent pulse fall time (90%/10%) of 46 ns at 1066 nm. Alternatively, for applications requiring faster speed, the device can be biased to 0.16 A/W with a fall time of 2.5 ns, or 0.07 A/W with a fall time of 0.8 ns.