InGaAs Communication Photodiodes: From Low- to High-Power-Level Designs

While InGaAs absorption material has been used for various applications up to 1.6-μm wavelength, specific designs for low-level detection have become of main interest using high responsivity and low-dark-current detectors. By adding an avalanche multiplication layer to form an avalanche photodiode (APD) using the Separated Absorption and Multiplication (SAM) structure, one can take advantage of the very low-noise properties of the multiplication process in large-bandgap AI(Ga)(ln)As material to improve receiver sensitivity by > 10 dB. Under high-power-level injection, specific PIN structures have been developed to improve space charge effects and linear operation as needed for power applications such as high bit rates using coherent detection or analog photonic links. Specific designs to achieve simultaneously broad bandwidth, high responsivity, very high power saturation, and high linearity will be discussed.