Detection of gas-phase species in MOCVD of GaN using molecular beam quadrupole mass spectrometry

The commercially applied procedure for GaN deposition using Ga(CH3)(3)/NH3 was investigated in a wide temperature region between 300 and 1500 K. Molec ular beam sampling using quadrupole mass spectrometry has been used to show that gallium-nitrogen compounds, like the Lewis-acid-base adduct (CH3)(3)G aNH3 and dimeric clusters like [(CH3)(4)Ga-2(NH2)(2)], [(CH3)(3)Ga-2(NH2)(2 )] and [(CH3)(3)Ga-2(NH)] appear in the boundary layer of a sapphire substr ate in the temperature range between 300 and 1000 K, whereas above 1000 K t he only species detected are Ga(CH3)(2), Ga(CH3) and mostly Ga atoms. There fore we conclude that mainly Ga atoms carry the flux of metal onto the subs trate where epitaxial growth takes place (> 1200 K). (C) 2000 Elsevier Scie nce B.V. All rights reserved.