Monolithic Integration of an Active InSb-Based Mid-Infrared Photopixel With a GaAs MESFET

Medium wavelength infrared (MWIR) detectors are of increasing importance in defense, security, commercial, and environmental applications. Enhanced integration will lead to greater resolution and lower cost focal plane arrays (FPAs). We present the monolithic fabrication of an active photopixel made in InSb on a GaAs substrate that is suitable for large-scale integration into an FPA. Pixel addressing is provided by the cointegration of a GaAs MESFET with an InSb photodiode (PD). Pixel fabrication was achieved by developing novel materials and process steps, including isolation etches, a gate recess etch, and low temperature processes, to make Ohmic contacts to both the GaAs and InSb devices. Detailed electrical and optical measurements in an FTIR demonstrated that the PD was sensitive to radiation in the range of 3-5 μm at room temperature, and that the device could be isolated from its contacts using the integrated MESFET. This heterogeneous technology creates great potential to realize a new type of monolithic FPA of addressable pixels for imaging in the MWIR range.