Grafted Low‐Leakage Si/AlN p‐n Diodes Enabled by Fluorinated AlN Interface

ABSTRACT Ultrawide‐bandgap AlN is promising for next‐generation power devices but is limited by unstable surface chemistry and defective oxides induced by high‐temperature rapid thermal annealing (RTA). Here, we demonstrate a fluorination‐based interface engineering strategy using AlF _x /SiN _x passivation for p‐Si/n‐AlN heterojunction diodes fabricated via semiconductor grafting. A low‐damage pseudo‐atomic layer etching process removes RTA‐induced oxides, followed by XeF ₂ treatment to form an ultrathin AlF _x layer, which is stabilized by an ALD‐grown SiN _x capping layer. The engineered interface significantly suppresses defect‐assisted leakage, reducing reverse current by several orders of magnitude while maintaining forward conduction. Temperature‐dependent measurements reveal suppression of Poole–Frenkel emission, with the remaining high‐field leakage likely associated with AlN epilayer quality. X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) confirm reduced AlO _x formation and the formation of a stable SiO _x /SiON/AlF _x interfacial layer. These results establish AlF _x as an effective passivation scheme for low‐leakage AlN‐based heterojunction devices.