Influence of V/III ratio on stress control in GaN grown on different templates by hydride vapour phase epitaxy

Abstract

GaN crystals were grown on MOCVD-GaN/Al₂O₃ templates (MGA) and MOCVD-GaN/6H–SiC templates (MGS) in a hydride vapour phase epitaxy (HVPE) process where the V/III ratio was controlled. The tensile stress that exists in MGS was controlled by an increasing V/III ratio. The compressive stress that appears in MGA was controlled by a decreasing V/III ratio. The mechanism of stress control using the V/III ratio is discussed in terms of the interrelation of the stress, the V/III ratio and the crystal growth. The stress in these two kinds of substrates causes differences in atomic mobility which may be compensated by varying the V/III ratio. It is found that a larger V/III ratio results in a higher atomic mobility. Thus, atomic mobility is retarded by compressive stress and increased by tensile stress. This method of stress control has been shown to provide worthwhile guidance for GaN growth on different templates, and under different conditions in other investigations.