Direct correlation of defects and dark currents of InGaAs/InP photodetectors

A direct correlation pathway has been established between the material defects and dark currents of InGaAs photodetectors, which is significant for demonstrating the focal plane array with large scale and small pixels. The same photodetector chip was characterized by using emission microscopy and dark current-voltage measurements. The chips with defect emissions perfectly match with those chips showing large dark currents. The defect emissions were observed for the chips with large dark currents, while did not for the chips with low dark currents. The measurement result of the transmission electron microscope reveals that those material defects correlated with the device dark currents were mainly originated from the interface of the substrate and InP buffer layer. This work clarifies the direct correlation of defect types and device performances, which indicates the direction of improving the photodetector materials.