Preliminary demonstration of diamond-GaN p–n diodes via grafting

Ultrawide bandgap (UWBG) semiconductors exhibit exceptional electrical and thermal properties, offering strong potential for high-power and high-frequency electronics. However, efficient doping in UWBG materials is typically limited to either n-type or p-type, constraining their application to unipolar devices. The realization of p–n junctions through heterogeneous integration of complementary UWBG (or WBG) semiconductors is hindered by lattice mismatch and thermal expansion differences. Here, we report the preliminary demonstration of diamond–GaN heterojunction p–n diodes fabricated via Grafting. A single-crystalline p+ diamond nanomembrane was integrated onto an epitaxially grown c-plane n−/n+ GaN substrate with an ultrathin ALD–Al2O3 interlayer. The resulting diodes exhibit an ideality factor of 1.55 and a rectification ratio of ∼104. Structural and interfacial properties were examined by AFM, XRD, Raman, and STEM, providing critical insights to guide further optimization of diamond–GaN p–n heterojunction devices.