A-plane (1120) InN has been successfully grown on R-plane (1012) sapphire substrate by electron cyclotron resonance (ECR) plasma-exited molecular beam epitaxy through substrate nitridation process. The substrate nitridation of R-plane sapphire by ECR nitrogen plasma was carried out at 430 °C for 10 and 15 min. The results of reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and scanning electron microscopy indicated the formation of A-plane InN on R-plane sapphire. Inclusion of cubic InN was also observed together with A-plane InN through RHEED and XRD measurements in case of A-plane InN layer grown on 10 min nitridated substrate. However, when the nitridation time of R-plane sapphire by ECR nitrogen plasma increased to 15 min, it is confirmed that formation of cubic InN was successfully suppressed.

We used electron cyclotron resonance plasma-excited molecular beam epitaxy (ECR-MBE) to grow Aplane (11 2 0) InN on nitridated R-plane (1 1 02) sapphire and then measured the structural properties using transmission electron microscopy (TEM). We determined the epitaxial relationship between A-plane InN and R-plane sapphire to be (11 2 0) InN // (1 1 02) sapphire and [1 1 00] InN // [11 2 0] sapphire . Moreover, the results indicated that the nitridation of the sapphire produced a (001) cubic AlN layer, and this layer caused the subsequent InN to have its a-axis normal to the interface. Also, by using two diffraction vector orientations in the TEM measurement, we found that dislocations with a screw component had a density of about 5 × 10 10 cm -2, which is about ten times higher than that with an edge component.