High Power Silicon-Germanium Photodiodes for Microwave Photonic Applications

We demonstrate high current operation of an evanescently coupled Ge waveguide n-i-p photodetector grown on top of a Si rib waveguide. A 7.4 μm × 500 μm device was found to dissipate 1.003 W of power (125.49 mA at -8 V). 2-D thermal simulations of the device show that the relatively high thermal conductivities of the intrinsic Ge region and the p⁺ doped Si layer result in efficient heat transfer and hence, lower absorber temperatures when compared to a similar InP based waveguide photodiode. Additionally, to determine the feasibility of these devices for analog photonic applications, we performed large signal and small signal radio frequency (RF) measurements as well as linearity measurements. At 1 GHz and 40 mA of photocurrent, a third order output intercept point (OIP3) of 36.49 dBm is measured. The maximum RF power extracted at 1 GHz is 14.17 dBm at 60 mA of photocurrent and 7 V reverse bias.