High Efficiency, Large-Area, 1550 nm InGaAs Photodiodes

A back-illuminated planar InGaAs photodiode tested to have 95% quantum effiiency (QE) at 1550 nm, area greater than 1 mm2, low capacitance (<23 pF), and high bandwidth (>125 MHz) will be improved. Although the existing Phase I device exhibited bulk material dark current generation better than commercially available devices, the sidewall-generated dark current was found to dominate the noise equivalent power (NEP) performance. With all other aspects of the device shown to meet the requirements of optical quantum state tomography, in Phase II, standard planar processing will be used to fabricate the innovation, so that the bulk-InGaAs dominated performance limit of less than 500 pA of dark current can be achieved. Pairs of detectors matched for rise and decay time with less than 0.1% subtraction mismatch under optical excitation by femtosecond laser source will be packaged for use by NIST in homodyne measurements.