Confinement‐Enabled Epitaxy of Single‐Crystal InN Fins Enables Room‐Temperature Ohmic Contact to GaN

ABSTRACT Indium nitride (InN) combines the highest electron mobility and peak carrier velocity among the III‐nitrides with an intrinsically degenerate surface accumulation layer, making it an attractive but difficult material for electronic interfaces. Here, we show that geometric confinement increases local adatom supersaturation and enables the growth of single‐crystal InN by standard pulsed metal–organic chemical vapor deposition under conditions that otherwise do not support planar InN. This approach yields single‐crystal InN fins through selective‐area growth and supports versatile AlN/InN and GaN/InN heterostructures. The resulting selectively grown InN fins form abrupt GaN/InN and AlN/InN heterointerfaces and exhibit exceptionally low‐resistance, anneal‐free ohmic behavior. When integrated as epitaxial contact layers in AlGaN/GaN heterostructure FinFETs, they enable room‐temperature contacts that outperform conventional high‐temperature alloyed contacts while preserving interface crystallinity. These results establish confinement‐enabled InN epitaxy as a route to low‐thermal‐budget, gate‐first GaN processing and highlight a broader strategy for contact engineering and heterogeneous integration in advanced nitride electronics.