The role of NH3 and hydrocarbon mixtures in GaN pseudo-halide CVD: a quantum chemical study

The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons–NH 3 –Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH 4 , C 2 H 6 , C 3 H 8 , C 2 H 4 , and C 2 H 2 ) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located π-complexes Ga…C 2 H 2 and Ga…C 2 H 4 were studied to determine a probable catalytic activity in reactions with NH 3 . A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C 2 H 4 and C 2 H 2 as auxiliary carbon reagents for the Ga-NH 3 and Ga-C-NH 3 CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis.