Developments in MCT and T2SL technology for HOT applications at Leonardo UK

HgCdTe (MCT) and Type-II Superlattices (T2LS) are the two most promising material systems for high performance, high operating temperature (HOT) infrared imaging applications. This paper discusses the latest developments at Leonardo UK in each material system and provides a performance comparison for HOT MWIR applications. The MCT arrays (640x512/16 μm) were grown on GaAs substrates by Metal Organic Vapor Phase Epitaxy (MOVPE). MOVPE enables precise band engineering of the MCT heterostructure to suppress dark currents while maintaining collection efficiency at high operating temperatures. This approach yields high operability (>99.99%), highly sensitive arrays with an average noise equivalent temperature difference (NETD) of 15 mK at 140 K with F/4 optics. An average high frequency residual spatial noise (HF RSN) of 14.7 mK has been achieved with only 0.1% of pixels showing a gain instability greater than 1.1%. HOT T2SL arrays (640x512/20 μm) on GaSb and GaAs substrates have also been developed in collaboration with Lancaster University. The nBn device architecture was used to suppress Shockley-Read and surface dark currents. The T2SLs on GaSb and GaAs achieved NETDs of 27.4 mK and 28.7 mK respectively when operated at 140 K with F/2 optics. The HF RSN for the T2SL on GaSb was 26.6 mK with only 0.4 % of pixels showing a gain instability greater than 1.1% and an operability of 97.73%. We conclude that both MCT and T2SL arrays demonstrate a clear advancement in HOT MWIR capability at Leonardo UK.