High quantum efficiency, long wavelength InP/InGaAs microcavity photodiode
There is an inherent tradeoff between the quantum efficiency and bandwidth of conventional pin photodiodes. In the case of devices based on III-V semiconductors, an absorption region thickness of approximately 2 μm is required to achieve quantum efficiencies greater than 80%, although this limits the transit-time-limited bandwidth to less than 15 GHz. It has recently been shown that a microcavity photodiode can circumvent this performance tradeoff and achieve both high quantum efficiency and large bandwidths. The fabrication of a microcavity pin photodiode with a high quantum efficiency near 1.55 μm is described. An external quantum efficiency of 82% at 1480 nm has been achieved with an InGaAs absorption layer only 2000 Å thick embedded in a resonant cavity grown by metal organic vapour phase epitaxy (MOVPE).
