Ultra Low Dark Current, High Responsivity and Thin Multiplication Region in InGaAs/InP Avalanche Photodiodes

A separate absorption, grading, charge and multiplication InGaAs/InP avalanche photodiode with ultra low dark current and high responsivity is demonstrated. It has a thin multiplication layer and a planar structure. Through the use of a well and a single floating guard ring to suppress edge breakdown, the device can easily be fabricated by one step epitaxial growth and one step diffusion. The dark current of a 30 μm diameter device is as low as 0.028 nA at punch-through and 0.1 nA at 90% of the breakdown voltage. The responsivity at 1.55 μm is 0.93 A/W at unity gain and the multiplication layer is estimated to be less than 300 nm.