Progress on type-II superlattice-based long-wavelength infrared photodetectors

In this paper, we report recent progress in Type-II superlattice (T2SL) based long-wavelength (LW) infrared photodetectors. The InAs/GaSb based LW superlattice structure has been redesigned for optimal photon absorbance, barrier performance for low dark current, and enhanced operability. Moreover, the superlattice structure was processed into 640×512, pixel pitch 15μm focal plane arrays (FPA) with a long-wavelength approximately ranging from 7.3-9.6μm, with simultaneous readout mode. Both dry etching and passivation for the detector devices were optimized during the process to achieve high quality disk mesa. Furthermore, after flip-chip bonded with customized read-out integrated circuits (ROIC), the noise equivalent temperature difference (NETD) of the FPAs were measured as 25.3mK, with response non-uniformity of 3.48%. The detectors presented high-quality infrared images with defective pixel densities under 0.1% for LW. Also, the aforementioned LW superlattice infrared photodetectors were designed for high operability, temporal stability, reproducibility, scalability, and cost effectiveness. This progress could pave the road for the production of ecomonic and high-performance T2SL based LW infrared photodetectors.