Effects of hydrogen etching on stress control in AlN interlayer inserted GaN MOVPE on Si

摘要

Clarification and control of the hydrogen etching of GaN is essential to achieving high-quality GaN-on-Si virtual substrates and devices based on it produced by metalorganic vapor phase epitaxy. This phenomenon and its effects on GaN-on-Si stress control were studied in this work. Without deliberate protection, voids with lateral sizes on the micrometre level underneath AlN interlayers emerged in GaN. Such voids made stress balancing in GaN-on-Si systems by inserting AlN interlayers less efficient. By flowing a protective large flow rate of ammonia, voids were eliminated while GaN decomposition still happened, which led to AlGaN alloy in the interlayers. Interfaces of Ga incorporated AlN interlayers grown under large-scale varied conditions were characterised by scanning transmission electron microscopy and energy dispersive spectrometry. Higher growth temperatures caused more Ga in the interlayers and weakened their capacity to induce compressive stress in the overlying GaN.