Effect of V/III ratio on the surface morphologies of N-polar GaN films grown on offcut sapphire substrates

High quality N-polar GaN films grown with varied V/III ratios by metal–organic vapor phase epitaxy

“…The rougher surface grown with the lower V/ III ratio was previously explained by the non-uniform island formation in the initial HT-GaN growth and severe stepbunching effect. 11 For Samples C-E, with increasing thickness of the low-V/III-ratio layer from 11 nm to 22 nm and to 86 nm, the RMS surface roughness was increased from 1.9 nm to 3.2 nm and to 8.3 nm. The surface roughness was reduced to 4.4 nm for Sample F, which should be attributed to a smoother buffer layer grown at a higher temperature (see Fig.…”

“…In our last work, we have observed larger size but lower density nuclei in the initial HT-GaN growth stage and a higher step-bunching effect under a condition of lower V/III ratio, which was believed to be the cause of the rougher surface. 11 In the proceeding growth, the large islands tended to coalesce and transit to a 2D-like growth mode. 11 In such a process, threading dislocations (TDs) can partially bend and annihilate and eventually result in an improved crystallinity, similar to that in the typical two-step growth of Ga-polar GaN.…”

“…11 In the proceeding growth, the large islands tended to coalesce and transit to a 2D-like growth mode. 11 In such a process, threading dislocations (TDs) can partially bend and annihilate and eventually result in an improved crystallinity, similar to that in the typical two-step growth of Ga-polar GaN. 10,16,17 Therefore, the lacking of the 3D-to-2D growth mode transition in the growth with a high V/III ratio can cause an inferior crystal quality.…”

Effects of V/III ratio of InGaN quantum well at high growth temperature for near ultraviolet light emitting diodes

“…In general, this condition arises in the diffusion growth-restricted regime when the Ga adatom molecules are shorter than the diffusion duration (Hussin et al , 2021; Jasik et al , 2009). At this regime, Ga atoms diffusion length is less than the atomic width terrace (Hussin et al , 2021; Li et al , 2020) leads to a rough surface.…”

“…Figure 1(a), 1(d) shows that the sample exhibits an unequal distribution of irregular structures with the largest peak to valley width and highest depth, which are ∼4 µm and ∼3 nm, respectively, under a low V/III ratio of 11824. Overall island growth (Li et al , 2020) and irregular island growth are promoted by high adatom diffusivities at low V/III ratios, further affecting layer instability (Hussin et al , 2021). In general, this condition arises in the diffusion growth-restricted regime when the Ga adatom molecules are shorter than the diffusion duration (Hussin et al , 2021; Jasik et al , 2009).…”