Several nitrogen precursors have been used for the growth of GaN in MO
VPE, but so far the best results were obtained using NH3, even though
NH3 does not produce a significant amount of active species at the gro
wing interface. To produce active species from N-2 or NH3, a remote pl
asma-enhanced chemical vapour deposition (RPECVD) process has been imp
lemented. In addition, nitrogen metalorganic precursors, triethylamine
and t-butylamine, were also used. To accurately control the critical
parameters of the MOVPE of GaN, we have implemented a laser reflectome
try equipment, which allows a real-time in situ monitoring of the diff
erent steps of the growth, i.e. nitridation of the substrate, nucleati
on, heat treatment, and deposition. Using an appropriate buffer layer,
GaN grown on sapphire using NH3 as nitrogen precursor, shows sharp lo
w temperature photoluminescence lines (4 meV at 9 K), whereas other ni
trogen precursors did not lead to comparable electronic quality.