Development of UV-optimized CMOS detectors for small planetary missions

We present progress toward optimizing the far ultraviolet (FUV, 100-200 nm) response of large-area Si-PIN diode hybrid CMOS imaging arrays produced by Teledyne Imaging Sensors (TIS) and high performance backside-illuminated silicon monolithic CMOS (BI-CMOS) sensors from Teledyne e2v. The improvement in FUV response is achieved by using a molecular beam epitaxy (MBE) process to dope the thinned backside of the detector wafers, creating a thin surface potential to improve the detection of UV photon generated holes at the illuminated surface. Our current project builds on previous work to optimize the MBE process at MIT Lincoln Laboratory using test wafers provided by TIS (Retherford et al., JATIS, 2015).

The FUV spectral region is important for planetary science, containing a large number of emission and absorption features of chemical species commonly found in planetary atmospheres and surfaces. Current state-of-the-art FUV instruments for planetary missions - including the Southwest Research Institute's UVS/Alice series - use microchannel plate (MCP) detectors, which require high voltage power supplies and have limited potential for further miniaturization. The doped CMOS detectors we are developing have the potential to facilitate more compact instrumentation with simultaneous FUV and mid UV (MUV, 200-300 nm) coverage, well suited to the growing niche of small satellite and CubeSat planetary science missions.