H(2)GaN(3) and Derivatives: A Facile Method to Gallium Nitride.

We describe the formation and properties of H(2)GaN(3) (1), which is a very simple and stable molecular source for chemical vapor deposition (CVD) of GaN heterostructures. Compound 1 and the perdeuterated analogue D(2)GaN(3) (2) are prepared by the LiGaH(4) and LiGaD(4) reduction of Br(2)GaN(3) (3), respectively. Compound 3 is obtained from the thermal decomposition of the crystalline adduct SiMe(3)N(3).GaBr(3) (4) via loss of SiMe(3)Br. A single-crystal X-ray structure of 4 reveals that the molecule is essentially a Lewis acid-base complex between SiMe(3)N(3) and GaBr(3) and crystallizes in the orthorhombic space group Pna2(1), with a = 14.907(5) Å, b = 7.759(3) Å, c = 10.789(5) Å, V = 1248(1) Å,(3) and Z = 4. The new azidobromogallane HBrGaN(3) (5) is also prepared by reaction of appropriate amounts of 3 and LiGaH(4). Both H(2)GaN(3) (1) and D(2)GaN(3) (2) are volatile species at room temperature and can be readily distilled at 40 degrees C (0.20 Torr) without decomposition. Normal-mode analysis and ab initio theoretical calculations suggest that the vapor phase IR spectra of 1 and 2 are consistent with a trimeric (H(2)GaN(3))(3) and (D(2)GaN(3))(3) molecular structure of C(3)(v)() symmetry. On the basis of the mass spectrum, 1 is a trimer in the vapor phase and decomposes readily at low temperatures by elimination of only H(2) and N(2) to yield pure and highly stoichiometric GaN thin films. Crucial advantages of this new and potentially practical CVD method are the significant vapor pressure of the precursor that permits rapid mass transport at 22 degrees C and the facile decomposition pathway that allows film growth at temperatures as low as 200 degrees C with considerable growth rates up to 800 Å/min.

Synthesis and Structure of a Novel Lewis Acid-Base Adduct, (H(3)C)(3)SiN(3).GaCl(3), en Route to Cl(2)GaN(3) and Its Derivatives: Inorganic Precursors to Heteroepitaxial GaN.

The formation of a novel Lewis acid-base complex between the silyl azide Si(CH(3))(3)N(3) and GaCl(3) having the formula (H(3)C)(3)SiN(3).GaCl(3)()()(1) is demonstrated. The X-ray crystal structure of 1 shows that the electron-donating site is the nitrogen atom directly bonded to the organometallic group. Compound 1 crystallizes in the orthorhombic space group Pnma, with cell dimensions a = 15.823(10) Å, b = 10.010(5) Å, c = 7.403(3) Å, and Z = 4. Low-temperature decomposition of 1 via loss of (H(3)C)(3)SiCl yields Cl(2)GaN(3) (2), which serves as the first totally inorganic (C,H-free) precursor to heteroepitaxial GaN by ultrahigh-vacuum chemical vapor deposition. A volatile monomeric Lewis acid-base adduct of 2 with trimethylamine, Cl(2)GaN(3).N(CH(3))(3) (3), has also been prepared and utilized to grow high-quality GaN on Si and basal plane sapphire substrates. The valence bond model is used to analyze bond lengths in organometallic azides and related adducts.