ORGANOMETALLIC PRECURSORS FOR THE FORMATION OF GAN BY METAL-ORGANIC CHEMICAL VAPOR-DEPOSITION - A STUDY OF [(CH3)2GANH2]3

The reaction of Ga(CH3)3 with an excess of ammonia leads to the formation of (CH3)3Ga.NH3, which, when heated at 120-degrees-C under 450 Torr nitrogen, decomposes to yield CH4 and the trimer [(CH3)2GaNH2]3 1 and not, as previously stated, a dimeric species. A single-crystal X-ray study of 1 revealed that it is a molecular species containing a (GaN)3 ring [Ga-N 1.93(2)-2.05(2) angstrom] in which four consecutive ring atoms are coplanar. The remaining two atoms of the ring are on the same side of the plane so the ring has the sofa conformation. The internal ring angles range from 93.8(8) to 101.3(8)-degrees (for N-Ga-N) and 119.5(9) to 125.3(9)-degrees (for Ga-N-Ga). Compound 1 is monoclinic, space group P2(1)/c, Z = 4. 985 Independent reflections have been measured on a diffractometer and the structure refined to R = 0.076. Spectroscopic evidence shows that 1 retains its trimeric nature in the gas phase. Thus, in the mass spectrum the parent ion is seen, while infrared spectra of mulls of solid 1, of gaseous 1 condensed onto Csl windows and of matrix-isolated 1 are in agreement with the same species being in both solid and gas phases.