Influence of MO-GaN templates on the HVPE growth of semi-polar GaN thick films

In this paper, the growth of semi-polar GaN thick films was investigated on an m-plane sapphire by hydride vapor phase epitaxy (HVPE). By optimizing parameters of the HVPE process, both (11-22) and (10-13) semi-polar GaN films have been successfully obtained with a mirror surface and excellent crystal quality on different GaN templates grown by metal organic chemical vapor deposition (MOCVD), respectively. The influence of MO-GaN templates on the HVPE growth was further studied. The results revealed that the same plane of a semi-polar HVPE-GaN thick layer was grown on a single-phase template, such as GaN (11-22)(HVPE) on (11-22)(MO-template) and GaN (10-13)(HVPE) on (10-13)(MO-template). However, on mixed-phase MO-templates, a single-phase (11-22) GaN thick layer was found to grow even if the original templates contain both (11-22) and (10-13) plane components. Meanwhile, in contrast with the difficult growth of GaN (10-13) with a smooth surface, it is easier to acquire GaN (11-22) thick layers by a HVPE method. A wider window for the growth of the (11-22) plane could partly explain the reason why the pure GaN (11-22) plane could be grown on mixed-phase ((11-22) & (10-13)) MO-templates. In order to explain this phenomenon, both formation energy (E-f) and migration barrier (E-m) of these semi-polar faces were calculated. Our results indicated that the E-f of GaN (10-13) (-0.56 eV) is higher than that of (11-22) (-10.73 eV), and the E-m of (10-13) (0.30 eV) is lower than that of (11-22) (1.89 eV). So the (11-22)-plane growth was more likely to be prevalent in competition between two phases.

Automated summary

This paper investigated the growth of semi-polar GaN thick films on an m-plane sapphire by HVPE, obtaining (11-22) and (10-13) films with mirror surfaces and excellent crystal quality on different GaN templates. The influence of MO-GaN templates on HVPE growth was studied, showing that single-phase growth was predominant on single-phase templates, while mixed-phase templates led to single-phase growth. Calculation of formation energy and migration barrier of semi-polar faces indicated that (11-22)-plane growth was more likely to occur due to lower barriers.