(Invited) Micro-Transfer Printing Technology for GaN Transistors

Gallium nitride (GaN) transistor technology has recently emerged as a clear contender for high performance solid-state power amplifier applications in the military and commercial sectors. GaN’s RF power density advantage stems from its large semiconductor energy bandgap, which allows it to be operated at higher voltage compared to conventional III-V and Si technologies. While GaN’s RF performance is amongst the best that is commercially available, its technology monolithic platform lacks several capabilities that would allow for the realization of high performance mixed signal circuits. For instance, since GaN transistors are only available in n-channel variants, there is currently no opportunity available to produce a low power consumption, high density complementary logic in GaN. One approach to bringing missing device functionality into contact with a technology like GaN is through a process termed “heterogeneous integration.” Over the past few years, several groups have investigated integrating circuits of different technologies (i.e. Si CMOS, InP, GaN, etc.) together through means of wafer bonding and through-substrate vias/interconnects.[1] This approach can be used to create multi-technology mixed signal circuits that show a clear performance benefit; however, long design and cycle time, and yield multiplication make this approach an expensive process with sub-circuit elements constrained by the thermal budget and process limitations of the parent technology. An alternative approach that we are investigating in this study is performing multi-technology integration at the device level through the use of micro-transfer printing. Micro-transfer printing employs the use of a photo-patternable polydimethylsiloxane (PDMS) stamp to precisely pick and place individual semiconductor devices from a source wafer to a target multi-technology circuit. This talk will describe our materials development efforts involving crystalline transition metal nitride materials that are nearly lattice matched to SiC and can be selectively etched away to achieve lift-off and transfer of fully-processed GaN transistors.[2,3] By using metal-organic chemical vapor deposition (MOCVD) to grow GaN high-electron-mobility transistors (HEMTs) on crystalline NbNx/SiC templates grown by molecular beam epitaxy (MBE), we have measured device electrical performance that is equivalent to that of devices grown directly on SiC. This work was sponsored by the Office of Naval Research. References [1] D. S. Green, C. L. Dohrman, J. Demmin, Y. Zheng, and T. Chang, "A Revolution on the Horizon from DARPA: Heterogeneous Integration for Revolutionary Microwave/Millimeter-Wave Circuits at DARPA: Progress and Future Directions," IEEE Microwave Magazine, vol. 18, pp. 44 - 59, (2017). [2] D. Meyer, B. Downey, D. S. Katzer, M. Ancona, S. Mack, and L. Ruppalt, “GaN on Anything.” Compound Semiconductor Magazine, pp. 44 – 49, (2017). [3] D. Meyer, B. Downey, D. Katzer, N. Nepal, V. Wheeler, M. Hardy, T. Anderson, and D. Storm, “Epitaxial Lift-off and Transfer of III-N Materials and Devices from SiC Substrates,” IEEE Transactions on Semiconductor Manufacturing, vol. 29, pp. 384 - 389, (2016).