Low-cost and high-gain silicide Schottky-barrier collector phototransistor integrated on Si waveguide for infrared detection

A two-terminal silicide Schottky-barrier collector phototransistor (SBCPT) integrated on a silicon-on-insulator waveguide was proposed and demonstrated using low-cost standard silicon processing technology. Owing to the current gain through the transistor action, the SBCPT at 5 V bias achieves a responsivity around 1550 nm of $\sim 150\text{mA}/\text{W}$ , which is approximately 17.6-fold larger than the corresponding Schottky-barrier photodiode (SBPD) having the same silicide absorber. The current gain thereby the responsivity of SBCPT may be further improved simply by reducing the base width. Moreover, the SBCPT at negative bias exhibits a very low dark current of $\sim 12\text{pA}$ owing to the presence of a reversely biased Si $p\text{-}n$ junction while with the responsivity and speed only slightly degraded as compared to the SBPD counterpart. The proposed detector can be utilized as an in-line or terminal optical monitor in low-cost all-silicon electronic-photonic integrated circuits.