Impact of O2 flow rate on the growth rate of ZnO(0001) and ZnO(0001‾) on GaN by plasma-assisted molecular beam epitaxy

• Published in: Physica Status Solidi (B): Basic Research Vol. 253; no. 8; pp. 1523 - 1528
• Main Authors: Adolph, David, Ive, Tommy
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.08.2016
• Subjects: MBE; molecular beam epitaxy; Oxygen; oxygen flow; plasma; plasma-assisted MBE; ZnO
• ISSN: 0370-1972; 1521-3951; 1521-3951
• DOI: 10.1002/pssb.201552764

We studied the effects of a varying O2 flow rate on the growth of ZnO(0001) and ZnO(0001‾) layers on GaN/Al2O3 templates by plasma‐assisted molecular beam epitaxy. The O2 flow rate through the O‐plasma source was varied between 0.25 and 4.5 standard cubic centimeters per minute (sccm) corresponding to a growth chamber pressure between 3.0×10−6 and 5.0×10−5 Torr. We found that the change of the O2 flow rate had a profound effect on the ZnO layer growth rate. A maximum growth rate was reached for an O2 flow rate of 1.0–2.0 sccm. The same growth rate dependence on the O2 flow rate was observed for ZnO(0001) layers that were grown on GaN/4H‐SiC buffer layers for verification. To assess the amount of active O contributing to the ZnO‐growth, the spectral composition of the plasma was investigated with optical emission spectroscopy. The integrated optical emission line intensity reached a maximum for an O2 flow rate between 1.0 and 2.0 sccm. Essentially all emission lines exhibited a maximum intensity for an O2 flow rate between 1.0 and 2.0 sccm thus coinciding with the flow rate yielding the maximum growth rate.