InSb Photodiodes for Monolithic Active Focal Plane Arrays on GaAs Substrates

We describe the development and optical characterization of a planar medium infrared (mid-IR) InSb photodetector on a GaAs substrate technology, capable of integrating MESFETs, to demonstrate a new active pixel device architecture. Our results pave the way for the development of integrated mid-IR focal plane array circuits on a single chip. Device structures with areas down to 0.0016 mm2were investigated. By deploying a silicon nitride passivation layer, we were able to reduce leakage current in reverse bias by up to 27% to yield an improved rectifier. Extensive optical characterization was carried out in the near- and mid-IR wavelength range. Responsivities of up to 3.54 A/W and quantum efficiency values above unity were obtained in the near-IR range as a consequence of illumination above the bandgap causing impact ionization. In the mid-IR range, responsivities of up to 0.97 A/W were observed. The bandwidth of the devices proved compatible with video-rate standard sampling rates.