Ultralow-Dark-Current CdHgTe FPAs in the SWIR Range at CEA and Sofradir

We report the first results of work carried out at CEA and Sofradir to build ultralow-dark-current focal-plane arrays (FPAs) in the short-wave infrared range (SWIR) for space applications. These FPAs are designed to detect very low flux in the 2-μm wavelength range. To this end, Sofradir has designed a source follower per detector read-out circuit (ROIC, 384 × 288, 15 μm pitch). This ROIC has been hybridized on different HgCdTe diode configurations processed at CEA-LETI, and low-flux characterizations have been carried out at CEA-IRFU at low temperature (from 60 K to 160 K). Both ion-implanted p/n and n/p diodes have been evaluated. The metallurgical nature of the absorbing layer has also been examined, and both molecular-beam epitaxy (MBE) and liquid-phase epitaxy (LPE) have been applied. Dark-current measurements are discussed in comparison with previous results from the literature. State-of-the-art dark currents are recorded for temperatures higher than 120 K. At temperatures lower than 100 K, the decrease in dark current flattens out for both technologies. In this region, currents between 0.4 e–/s/pixel and 0.06 e–/s/pixel are reported.