A low dark-current, planar InGaAs p-i-n photodiode with a quaternary InGaAsP cap layer.

In(0.53)Ga(0.57)As p-i-n photodiodes have become the most suitable photodetectors for long wavelength (1-1.65 microns) optical fiber communication systems due to their low dark-currents of the order of a few nanoamperes. Further reduction of dark- current to subnanoampere range will bring improvement in the receiver sensitivity. In this paper we report the successful fabrication of In(0.53)Ga(0.47)As p-i-n diodes with dark-currents as low as 0.1 nA at -10V bias by introducing a quaternary InGaAsP cap layer on the ternary InGaAs. In this new structure the InGaAsP cap layer undergoes the surface treatment and faces dielectric silicon nitride film, but the p-n junction is still located inside the InGaAs layer.