Formation of a tetrameric, cyclooctane-like, azidochlorogallane, [HClGaN₃]₄, and related azidogallanes. Exothermic single-source precursors to GaN nanostructures

The synthesis of a novel tetrameric gallane, [HClGaN₃]₄ (1), with a heterocyclic cyclooactane-like structure has been demonstrated. A single- crystal X-ray study reveals that the molecule consists of eight-membered Ga₄N₄ rings with Ga atoms bridged by the α-nitrogens of the azide groups. [HClGaN₃]₄ crystallizes in the tetragonal space group space group P4₂bc, with a = 17.920(3) Å, c = 10.782(3) Å, V = 3462(2) ų, and Z = 8. On the basis of the mass spectrum, the vapor of the compound consists of the trimer [HC1GaN₃]₃, which is a low-temperature molecular source for growth of GaN layers on sapphire and Si substrates at 500 °C. Solid 1 decomposes exothermically at 70 °C to yield bulk nanocrystalline wurtzite and zinc blende GaN. The reaction between H₂GaCl and LiN3 yields the analogous and extremely simple azidogallane (H₂GaN₃)(n) (2), which is used to deposit crystalline GaN films at 450 °C. Compound 2 is considerably more reactive than 1, and its decomposition, often initiated at room temperature, yields pure and crystalline nitride material of unusual morphology and microstructure.