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

摘要

The commercially applied procedure for GaN deposition using Ga(CH_3)_3/NH_3 was investigated in a wide temperature region between 300 and 1500 K. Molecular beam sampling using quadrupole mass spectrometry has been used to show that gallium-nitrogen compounds, like the Lewis-acid-base adduct (CH_3)_3GaNH_3 and dimeric clusters like[(CH_3)_4Ga_2(NH_2)_2], [(CH_3)_3Ga_2(NH_2)_2] and [(CH_3)_3Ga_2(NH)] appear in the boundary layer of a sapphire substrate in the temperature range between 300 and 1000 K, whereas above 1000 K the only species detected are Ga(CH_3)_2, Ga(CH_3) and mostly Ga atoms. Therefore we conclude that mainly Ga atoms carry the flux of metal onto the substrate where epitaxial growth takes place (>1200 K).