N-on-p extrinsically doped MWIR HgCdTe material and photodiodes have been developed to benefit from the expected reduction of the Auger generation in the p-type absorbing layer. Samples with two doping levels have been characterized using dark current, current noise, Hall effect and PhotoLuminescence Decay (PLD) measurements. The dark current and PLD measurements are consistent with a reduction of the Auger generation quantified by the ratio between the Auger 1 and 7 recombination coefficients 𝛾 around 10. The corresponding dark current in the sample with the lowest doping level was slightly higher than in typically p-on-n photodiodes. The low frequency noise, characterized by a Tobin coefficient below 10-5, is lower than the values reported for other MWIR HgCdTe photodiodes at the same dark current density. The low dark current and dark current noise show on the high potential of such photodiodes to form focal plane array that can be operated at high operating temperature without degradation of the image quality.
This LETI/Sofradir/Defir study aims at realizing sub-10 μm pitch HgCdTe infrared FPAs. To cope with the different diode process issues related to pitch reduction-morphologic realization, short-circuits, FTM optimization - a parametric study was carried out - contact size, passivation properties, doping levels, diode processing conditions-. A wafer-level test campaign was conducted to evaluate the process window. It revealed functional MWIR diodes from 15 μm to 3 μm pitch. 7.5 μm pitch 640×512 and 5 μm pitch 64×152 FPA were characterized and turned out to be functional.