Studies of the plasma related oxygen contamination of gallium nitride grown by remote plasma enhanced chemical vapour deposition

Nitrogen and ammonia plasma containment tubes of quartz and fused alumina (Al₂O₃) are evaluated in terms of the oxygen contamination contributed during gallium nitride film growth by RPE-CVD. In-situ gas and plasma monitoring, and material characterisation (UV-Vis transmission measurements, X-ray diffraction and SIMS) were used to determine the contaminant chemistries for the plasmas maintained in these containment tubes. Oxygen contamination using a quartz tube is shown to be unavoidable. Al ₂O₃ based tubes used with an ammonia plasma also supply unacceptably high levels of oxygen for GaN growth. However, we show that alumina containment tubes may be conditioned in a nitrogen plasma, so that an aluminium nitride protective layer limits the oxygen contamination.