III-V Microsystem Components for Positioning, Navigation and Timing in Extreme Harsh Environments

The development of III-V microsystems technology can aid in improving the precision, robustness and weight of positioning, navigation and timing (PNT) systems used in deep space exploration. State-of-the-art PNT components require complex packaging, are limited to temperatures below 200°C and are prone to radiation degradation. As a result, new material platforms that utilize radiation tolerant, wide bandgap, III-V semiconductor materials are proposed to develop spaceborne microsystems components. In the proposed work, two types of microsystems components (resonators and sensors) that can withstand the harsh deep space environment will be developed. The scope of the proposed research is to 1) develop piezoelectric resonators with Q-enhancement and temperature compensation features, 2) develop III-V sensors (e.g. sun and inertial sensors) for future spaceborne sensor ensembles, and 3) perform experimental exposure testing (e.g. thermal cycling and radiation) of sensor materials and actual microsystem devices for evaluation. Gallium nitride (GaN) and aluminum nitride (AlN) will be investigated as the materials platform for the microsystem components. The tasks proposed in this work aid in the realization of advanced components for timekeeping/frequency referencing as well as positioning and maneuvering (TA05). In addition, the use of radiation-hardened materials (less packaging requirements) to create micro-scale components can aid in the development of lightweight structures (TA12). Ultimately, the III-V microsystems technology developed in this program can aid in precision landing, hazard avoidance, formation flying and autonomous docking. 
•Demonstrated radiation tolerance(up to 850kRad)of GaN-on-sapphire surface acoustic wave resonators and identified the physical characteristics of GaN-on-sapphire surface acoustic wave resonators using materials microscopy.
•Demonstrated the cryogenic response(temperatures as low as-180°C) of GaN-on-sapphire surface acoustic wave resonators(SAW)for the first time. This experimental testing GaN-based surface acoustic wave SAW resonators revealed significant improvement in temperature sensitivity and a unique temporal response (self-compensating) at cryogenic temperatures, which has been unreported to date.
•Gamma irradiation (up to 850 kRad TID) and electrical characterization of GaN-based UV photodetectors has been completed and characterization reveals that thermal annealing enables recovery of electrical response, performed with NASA Ames Research Center collaborators. Transmission electron microscopy (TEM) images were obtained to identify defects in the GaN layer after Co-60 irradiation.
•Transparent, conductive graphene/GaN and graphene/AlGaN/GaN UV metal-semiconductor-metal (MSM) photodetector devices, high electron mobility transistors (HEMTs) and diodes successfully fabricated and tested under gamma and proton irradiation up to 750 krad and 1013protons/cm2, respectively.
•Systems-level preparation for graphene-GaN sun sensor inclusion in QB50 cubesat launch, including micro sun sensor preparation (assembly and testing) and continued meetings with hardware, software and data QB50 design teams to refine the design and create a mock set-up to test the sun senor interface with the QB50 electrical and software design.
•The design, fabrication and high-temperature characterization (up to 550°C) of AlGaN/GaN strain sensing elements for inertial sensor design has been completed.
•Advanced fabrication technology (microstructure release and metallization) for AlGaN/GaN microsystems have been developed and demonstrated confirming that monolithic integration of sensors with AlGaN/GaN transistors is feasible.
•Thermal storage tests of high-temperature, metal multilayers used in harsh environment GaN device design demonstrated stable operation for 10 hours in air at temperatures as high as 600°C.
•Research activities from this program have resulted in 9 technical publications to date including NASA collaborator co-authorship. It should also be noted that, 5additional publications(journal articles)are in preparation.