Congratulations to Owen Meilander and his collaborators! Owen鈥檚 paper, 鈥淢icro-transfer printing of GaN HEMTs on engineered substrates for use in harsh environments,鈥� has been featured as a VINSE Spotlight publication and published in APL Electronic Devices. This work was carried out in the Mona Ebrish Lab, with contributions from co-author and former VINSE REU summer fellow Lisa Sebastian.
Gallium nitride (GaN) high electron mobility transistors (HEMTs) promise high efficiency and performance for high-power and high-frequency applications due to its wide bandgap and high electron mobility. However, the lack of native complementary logic in GaN necessitates its integration with standard CMOS controllers. While discrete packaging on a PCB level provides a temporary solution, it compromises device efficiency and size, driving the need for a scalable, direct on-chip heterogeneous integration method.
In this work, we demonstrate a scalable heterogeneous integration approach utilizing micro-transfer printing to bond GaN HEMTs released from 8-inch, CMOS-compatible Qromis Substrate Technology wafers to arbitrary target substrates. By selectively etching a silicon seed layer and employing a PDMS stamp for deterministic placement, this technique achieved a transfer success rate exceeding 95% with minimal device degradation after bonding. Our results reveal that managing residual biaxial stress is critical. By controlling the thickness of the buffer layers beneath the active device, the observed strain relaxation resulting in a more than 12 渭m bend across the transferred layer was reduced to less than 1 渭m. Finally, the transferred devices proved robust against extreme environmental conditions. They survived both the vacuum of space and temperature fluctuations from 8 to 473 K without delamination or loss of electrical performance. This industry-compatible methodology offers a viable pathway for integrating GaN power electronics into next-generation systems, paving the way for more efficient and compact technology operating in the most demanding environments.
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Authors: O.R. Meilander, L. Sebastian, E. Riglioni, H.E. Dishman, and M.A. Ebrish
Abstract: Heterogeneous integration of gallium nitride (GaN) devices is essential to overcome the intrinsic material limitations in advanced electronics. For the successful incorporation of an integration technique into industry, a highly scalable process must be developed. In this work, the heterogeneous integration of GaN high electron mobility transistors (HEMTs) through a micro-transfer printing process is demonstrated. This scalable technique involving HEMTs fabricated on commercially available and CMOS-compatible 8鈥测�� GaN on engineered substrate resulted in a high (>95%) transfer success rate and limited device degradation. Transfer was demonstrated to multiple adhesion layers, including copper tape and KMSF 1000 photo-dielectric. The limited degradation that was observed is attributed to a change in stress after transfer, as measured
by the Raman spectroscopy. Finally, the viability of the adhesion layer for use in harsh environments was tested. No delamination, significant outgassing, or degradation of electrical properties were observed when the sample was placed under a vacuum or when the temperature was varied between 8 and 473 K. This makes the process an ideal choice for systems intended for space applications.