H2GaN3 and derivatives: A facile method to gallium nitride

We describe the formation and properties of H2GaN3 (1), which is a very sim ple and stable molecular source for chemical vapor deposition (CVD) of GaN heterostructures. Compound 1 and the perdeuterated analogue D2GaN3 (2) are prepared by the LiGaH4 and LiGaD4 reduction of Br2GaN3 (3), respectively. C ompound 3 is obtained from the thermal decomposition of the crystalline add uct SiMe3N3. GaBr3 (4) via loss of SiMe3Br. A single-crystal X-ray structur e of 4 reveals that the molecule is essentially a Lewis acid-base complex b etween SiMe3N3 and GaBr3 and crystallizes in the orthorhombic space group P na2(1), with a = 14.907(5) Angstrom, b = 7.759(3) Angstrom, c 10.789(5) Ang strom, V = 1248(1) Angstrom(3) and Z = 4. The new azidobromogallane HBrGaN3 (5) is also prepared by reaction of appropriate amounts of 3 and LiGaH4. B oth H2GaN3 (1) and D2GaN3 (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 t he vapor phase IR spectra of 1 and 2 are consistent with a trimeric (H2GaN3 )3 and (D2GaN3)(3) molecular structure of C-3v symmetry. On the basis of th e 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 high ly stoichiometric GaN thin films. Crucial advantages of this new and potent ially practical CVD method are the significant vapor pressure of the precur sor that permits rapid mass transport at 22 degrees C and the facile decomp osition pathway that allows film growth at temperatures as low as 200 degre es C with considerable growth rates up to 800 Angstrom/min.