Commercialization readiness of HOT LWIR detectors based on InAs/InAs1-xSbx T2SL at VIGO System S.A.

The InAs/InAsSb superlattices are attractive materials for the replacement of both RoHS restricted bulk HgCdTe and strongly Shockley-Read (SR) generation limited InAs/GaSb superlattices. Two main factors limit the performance of InAs/InAsSb photodiodes: the rate of the SR processes, especially in the depletion region, which is the source of the large dark current and a short vertical diffusion length of charge carriers in superlattice absorbers which results in poor responsivity. In this paper, we report on the status of HOT LWIR detectors based on InAs/InAsSb superlattices at VIGO System S.A. The uncooled and Peltier cooled LWIR photoconductors are the most successful devices developed so far. The practical InAs/InAsSb SL-based photoconductors have been fabricated by MBE heteroepitaxial growth on buffered 3” wafers. The design of the devices, material composition and doping, has been optimized for operation at temperatures from 200 to 300 K at a spectral range up to 18 μm. Some of the detectors were supplied with immersion microlenses formed in the GaAs substrates. The devices were characterized by measurements of the spectral responsivity and frequency-dependent noise density. The measured spectral detectivities of the best SL devices were found to be close or better compared to the HgCdTe counterparts operating at the same conditions. The devices are now offered as commercial products. Vigo present efforts are focused on the development of HOT LWIR photodiodes including monolithic cascade devices and thin absorber devices with the plasmonic enhancement of absorption. The development roadmap of advanced HOT devices is also sketched.