Structural properties of GaN grown by MOVPE turbodisc mass-production reactor

The structural properties of GaN films grown on sapphire in a turbodisc multiwafer reactor have been investigated using high-resolution X-ray diffraction and transmission electron microscopy. We found that the line shape of the (0 0 2) rocking curve can be fitted with two peaks. Therefore, we suggest that the GaN films consist of two layers: one related to extended structural defects such as dislocations originating from the film-buffer layer interface and one that is of high quality. The crystalline quality of the second layer continues to improve with increasing layer thickness. We also show that the relatively large width of the (0 0 2) peaks (270 arcsec for a 3 mu m film) has no causal link with the GaN film quality. In contrast, we demonstrate that there is a correlation between the in-plane structural features and optical and electrical properties. Using the (1 0 2) asymmetric reflection, 2 " wafer mapping of the (1 0 2) peak width closely mimics the resistivity mapping and photoluminescence intensity mapping. The (1 0 2) peak width is also sensitive to growth conditions of the buffer layer. By optimization of the buffer layer, the (1 0 2) peak width can be reduced to less than 600 s for a 3 mu m GaN film. A uniformity better than 2% can be achieved in both the (1 0 2) width and the resistivity mapping over 2 " wafers for all six wafers in the same growth run.