Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition

Gallium nitride (GaN)
is the main component of modern-day high
electron mobility transistors due to its favorable electronic properties.
As electronic devices become smaller with more complex surface architecture,
the ability to deposit high-quality GaN films at low temperatures
is required. Herein, we report a new highly volatile Ga­(III) triazenide
precursor and demonstrate its ability to deposit high-quality epitaxial
GaN by atomic layer deposition (ALD). This new Ga­(III) triazenide,
the first hexacoordinated Ga–N bonded precursor used in a vapor
deposition process, was easily synthesized and purified by either
sublimation or recrystallisation. Thermogravimetric analysis showed
single-step volatilization with an onset temperature of 155 °C
and negligible residual mass. Three temperature intervals with self-limiting
growth were observed when depositing GaN films. The GaN films grown
in the second growth interval at 350 °C were epitaxial on 4H–SiC
without an AlN seed layer and found to have a near stoichiometric
Ga/N ratio with very low levels of impurities. In addition, electron
microstructure analysis showed a smooth film surface and a sharp interface
between the substrate and film. The band gap of these films was 3.41
eV with the Fermi level at 1.90 eV, showing that the GaN films were
unintentionally n-type-doped. This new triazenide precursor enables
ALD of GaN for semiconductor applications and provides a new Ga­(III)
precursor for future deposition processes.