4.5 Influence of Growth Conditions on Epitaxial Layer Quality …
61
Low pressure
High pressure
Fig. 4.15 Schematic diagram of the change of the buffer layer under different pressure
Fig. 4.16 Schematic diagram of different growth pressure of the coarsening layer. a Under low
pressure and b under high pressure
The buffer layer grown under low pressure also causes an increase in the dislocation density and a decrease in crystal quality. Together with the buffer layer variation
diagram shown in Fig. 4.18, we can explain why a low-pressure during film growth
causes the deterioration of crystal quality. The vertical line in the figure represents
the edge dislocation, and the oblique line represents the mixed type threading dislocation. In the actual physical process, new edge dislocations will be formed when
the islands merge. Most of these dislocations will penetrate the thickness of GaN
epitaxial layer. Due to the presence of mixed dislocations, interaction occurs when
61
Low pressure
High pressure
Fig. 4.15 Schematic diagram of the change of the buffer layer under different pressure
Fig. 4.16 Schematic diagram of different growth pressure of the coarsening layer. a Under low
pressure and b under high pressure
The buffer layer grown under low pressure also causes an increase in the dislocation density and a decrease in crystal quality. Together with the buffer layer variation
diagram shown in Fig. 4.18, we can explain why a low-pressure during film growth
causes the deterioration of crystal quality. The vertical line in the figure represents
the edge dislocation, and the oblique line represents the mixed type threading dislocation. In the actual physical process, new edge dislocations will be formed when
the islands merge. Most of these dislocations will penetrate the thickness of GaN
epitaxial layer. Due to the presence of mixed dislocations, interaction occurs when