Below Rule’07 low dark current LWIR and VLWIR MCT 2D focal plane detector arrays from AIM

In recent years, high-operation temperature (HOT) detector applications in the mid-wave infrared spectral range (MWIR) have widely attracted attention [1, 2]. In the LWIR and VLWIR spectral ranges, an increase in operating temperature while keeping the detector performance obtained at lower temperatures proved to be significantly more difficult. The demands on detector material quality and detector processing are much higher. With LWIR HOT detector applications more and more evolving, AIM as a leader in LWIR MCT detectors has addressed the challenge. We like to note that AIM has a long standing track record on dark-current reduction, especially by extrinsic Au doping in the LWIR and VLWIR spectral range [3, 4, 5, 6]. During the last couple of years we matured our p-on-n LWIR technology, a key technology for high-performance small pixel pitch planar LWIR HOT MCT devices [9]. In this paper we present the status of our n-on-p and p-on-n low dark current planar MCT photodiode technology. The development was funded by ESA TRP contracts and resulted in follow-on contracts to even further optimize LWIR and VLWIR MCT and corresponding ROICs, especially for low-temperature, large area, astronomy applications. AIM’s manufacturing of HOT MCT devices is based on the liquid phase epitaxial (LPE) growth on latticematched in-house grown CdZnTe (CZT) substrates from a Te-rich melt, using the vertical dipping method [7, 8]. This method allows growing large MCT wafers with currently fair homogeneity in layer thickness (±1μm) as well as in composition (±0.3μm cut-off wavelength) across an area of 1.5 inch diameter in the LWIR-VLWIR cut-off wavelength range. We have investigated and compared technological constraints and performance of n-on-p and p-on-n growth for different doping levels and other process parameters. In the following we present the results for both technologies on 512 x 320 pixel format arrays with 20μm pixel pitch.