AbstractNanoscale air channel transistors (NACTs) have received significant attention due to their remarkable high‐frequency performance and high switching speed, which is enabled by the ballistic transport of electrons in sub‐100 nm air channels. Despite these advantages, NACTs are still limited by low currents and instability compared to solid‐state devices. GaN, with its low electron affinity, strong thermal and chemical stability, and high breakdown electric field, presents an appealing candidate as a field emission material. Here, a vertical GaN nanoscale air channel diode (NACD) with a 50 nm air channel is reported, fabricated by low‐cost IC‐compatible manufacturing technologies on a 2‐inch sapphire wafer. The device boasts a record field emission current of 11 mA at 10 V in the air and exhibits outstanding stability during cyclic, long‐term, and pulsed voltage testing. Additionally, it displays fast switching characteristics and good repeatability with a response time of fewer than 10 ns. Moreover, the temperature‐dependent performance of the device can guide the design of GaN NACTs for applications in extreme conditions. The research holds great promise for large current NACTs and will speed up their practical implementation.