Graphene‐Analogous Monolayer Boron Pnictides for High‐Mobility Electronics

Monolayer hexagonal phase boron pnictides are graphene‐analogous semiconductors, which are predicted to inherit a Dirac‐like electronic structure that promises intrinsically high carrier mobility for next‐generation electronics. However, their development has been experimentally hindered by the inherent instability of the hexagonal phase under ambient and growth conditions. Here, we overcome this fundamental challenge by employing a sub‐nanometer‐scale confined growth strategy within single‐walled carbon nanotubes (SWCNTs), which enables the first synthesis of stable, monolayer hexagonal boron phosphide (h‐BP) and boron arsenide (h‐BAs). The interfacial interactions between host‐guest materials within the confined space are shown to be crucial for obtaining intrinsically metastable hexagonal phase boron pnictides (B‐Pn) which are inaccessible through conventional synthesis methods. Notably, the h‐BP‐filled s‐SWCNTs heterostructure (h‐BP@s‐SWCNTs) exhibits a near 15‐fold enhancement in carrier mobility compared to pristine s‐SWCNTs (the highest reaching up to 526.9 cm 2 ·V −1 ·s −1 ), which represents a high‐performance level for FETs based on aligned s‐SWCNTs arrays. This research marks a breakthrough for interface engineering and band structure modulation to access metastable low‐dimensional nanostructures, toward next‐generation interface‐engineered, high‐performance nanoelectronics.