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.