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.