Because of the inevitable Fermi level pinning on surface/interface states of nanowires, achieving high-performance nanowire devices with controllable nanoscale contacts is always challenging but important. Herein, single-crystalline heterostructured Ga/GaAs nanowires with sharp hetero-Schottky interfaces have been successfully synthesized on amorphous substrates by utilizing Au nanoparticles as catalytic seeds via chemical vapor deposition. These nanowires are found to grow with the hemispherical Au7Ga2 catalytic tips following the vapor-liquid-solid mechanism. During the growth, simply by manipulating the source and growth temperatures, the Ga precipitation rate from Au-Ga alloy tips as well as the reaction rate of Ga precipitates with As can be reliably controlled in order to tailor the length (0-170 nm) of Ga nanowire segments obtained in the heterostructure. When configured into field-effect transistors, these Ga/GaAs NWs exhibit the p-type conductivity with a sharp hetero-Schottky barrier of similar to 1.0 eV at the atomically connected Ga segment/ GaAs NW body interface, in which this barrier height is close to the theoretical difference between the GaAs Fermi level (5.15.3 eV) and the Ga work function (similar to 4.3 eV), suggesting the effective formation of nanoscale contact by minimizing the Fermi level pinning, being advantageous for advanced nanoelectronics.