Dark current optimisation of 2.5 μm wavelength, 2% mismatched InGaAs photodetectors on InP

In this paper we report state-of-the-art dark current densities for 2% mismatched In_0.82Ga_0.18As photodetectors, for 2.5 μm wavelength light absorption. This is obtained by tuning the n-type doping level of the detector´s absorbing layer. Detectors with a 5×10¹⁶/cm³ doped absorbing layer exhibit a median dark current density of only 10^-9 A/cm² (at -10 mV bias and 150 K). Measurement of the dark current as a function of temperature give qualitative as well as quantitative information on the different mechanisms contributing to the dark current. The reduction of the photoresponse remains acceptable for the optimised doping of the absorbing layer. The cut-off wavelength is about 2.6 μm