Growth of non-polar a-plane and cubic InN on r-plane sapphire by molecular beam epitaxy

摘要

Growth of non-polar III-nitrides has been an important subject recently due to its potential improvement on the efficiency of III-nitride-based opto-electronic devices. Despite study of non-polar GaN and GaN-based heterostructures, there are few reports on epitaxial growth of non-polar InN, which is also an important component of the III-nitride system. In this study, we report heteroepitaxial growth of non-polar InN on r-plane sapphire substrates using plasma-assisted molecular beam epitaxy. It is found that when a GaN buffer is used, the following InN film appears to be non-polar (1120) a-plane which follows the a-plane GaN buffer. The room temperature Hall mobility of undoped a-plane InN is around 250 cm~2/Vs with a carrier concentration around 6x10~(18) cm~(-3). Meanwhile, if InN film is directly deposited on r-plane sapphire without any buffer, the InN layer is found to consist of a predominant zincblende (cubic) structure along with a fraction of the wurtzite (hexagonal) phase with increasing content with proceeding growth.