Micro-transfer Printing of GaN HEMTs for Heterogeneous Integration and Flexible RF Circuit Design

Abstract

Heterogeneous integration of complementary materials and device technologies is a demonstrated pathway for meeting the demand for next generation RF and mixed-signal circuits and has historically been accomplished via chip or circuit level wafer bonding and through-substrate vias [1] . A more intimate approach is integration at the device level via a micro-assembly technique such as micro-transfer printing [2] , which uses a polymer stamp to pick-and-place individual devices released from a source substrate to a multi-technology target substrate with micron-level alignment accuracy. This approach decouples the device technology from the growth substrate and enables technology agnostic circuit design and application-specific substrate choice. Here we demonstrate micro-transfer printing of GaN high-electron-mobility transistors (HEMTs) released from SiC growth substrates to other technologically relevant substrates such as Si and diamond. We show that there is no significant degradation in DC electrical characteristics after transfer printing, improved thermal performance can be achieved when the devices are transferred to single crystal diamond, and that post-transfer processing, such as interconnect metallization is possible with standard 2D lithographic techniques.