We report the first demonstration of an 8-in. N-polar GaN HEMT wafer using a wafer bonding and layer transfer approach. By growing the device layers on low-resistivity Si and transferring them onto high-resistivity Si substrates, we successfully integrated high-quality N-polar GaN/AlGaN heterostructures on scalable, low-loss silicon platforms. The fabricated wafer exhibits excellent surface morphology (RMS roughness 0.5 nm), improved crystallinity, low RF loss (∼0.4 dB/mm at 50 GHz), and low buffer leakage. Standard HEMT devices fabricated on the wafer demonstrate promising characteristics, including reasonable contact and sheet resistances, and a 2DEG mobility of up to 1390 cm2/V s, albeit with a relatively high off-state leakage current. Numerical simulation reveals that this leakage is mainly due to the thick channel and back-barrier design, which can be mitigated in future iterations. This work establishes a scalable path toward high-frequency, high-power N-polar GaN HEMTs on large-area substrates suitable for next-generation wireless and radar systems.
Li et al. (Sun,) studied this question.