Effect of defects on the luminescence in semipolar InGaN/GaN quantum wells on planar and patterned m‐plane sapphire substrate

Abstract

The correlation between luminescence and defects was investigated by the structural and optical analyses of semipolar InGaN/GaN quantum wells (QWs) grown on a planar m-plane sapphire substrate and patterned m-plane sapphire substrate using metal organic chemical vapor deposition. Scanning electron microscopy images indicated that the semipolar InGaN/GaN QWs grown on the planar substrate had high density of small arrowhead-like features on the surface, while those grown on the patterned sapphire substrate (PSS) had low density of large arrowhead-like features. Moreover, for the PSS sample, low defect regions were formed by periodically aligned patterns that reduced defect density, as verified by transmission electron microscopy. The monochromatic cathodolumine-scence images revealed that the luminescence of the planar sample was affected by the arrowhead-like features and high internal defect density, whereas that of the PSS sample was more influenced by the regions with reduced defects, as indicated by bright spotty features. Furthermore, the microphotoluminescence mapping images showed increased In incorporation where the arrowhead-like features were present. In particular, for the PSS sample, the wavelength of the luminescence from the reduced defect region was approximately 5 nm shorter than that from the region with a high density of internal defects. This result suggests that In incorporation was also increased in the high defect region.

Characterization of a-plane InGaN light-emitting diodes with a SiNx interlayer grown on a patterned sapphire substrate by metal–organic chemical vapor deposition

“…For this reason, the wavelength of the InGaN LED becomes longer and is blue-shifted because of the band filling effect resulting from an increase in current injection. 19) In contrast, the GaN grown on HPSS was divided into two regions: the low-defect region on a pattern region and the high-defect region on a flat region of the sapphire substrate. Therefore, indium atoms are segregated at the high-defect region (on the flat region of the substrate).…”

“…This suggests that both the low defect density and smooth surface morphology of the template are necessary for the growth of high-quality InGaN MQWs. 18,19) The AFM images in Figs. 4(d SiN x + HPSS LED suggests that the reduction in the defects density rather than the enhanced LEE, was the dominant factor in the improvement of optical power using HPSS.…”

“…In addition, at higher drive currents, the emission wavelength is determined by the quantum-well recombination in the defect-free regions. 19) These blue shifts of the planar LED and SiN x LED were caused by the high density of internal defects in the template and the indium segregation at the rough surface morphology. The wavelength of the SiN x LED was the largest among the three LEDs, suggesting that the surface defects (rough surface morphology) could be caused by the highly doped indium in MQW layers, 19) rather than the internal defects.…”

Strain relaxation of thick (11–22) semipolar InGaN layer for long wavelength nitride-based device

“…20,[24][25][26] In addition, phase separation and indium content fluctuations in InGaN layers could increase owing to defects or surface roughness. [27][28][29] Therefore, a (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) semipolar InGaN layer grown on an ELO GaN template was analyzed to minimize the effect of surface roughness and defects. Figure 3 shows plan-view SEM images ((a) ELO GaN template, (b) (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) semipolar GaN template) and a crosssectional STEM image of the InGaN layer grown on an ELO GaN template.…”

Growth of semipolar {20–21} GaN and {20–2–1} GaN for GaN substrate

“…Nonpolar growth techniques using the c-plane-like sapphire sidewall of patterned substrates are very effective for obtaining semipolar GaN layers because, in theory, all orientations can be realized. Semipolar {11-22}, {10-11}, and {20-21} GaN layers were grown on the PSSs by this method [20][21][22][23][24]. Furthermore, we reported the growth of thick semipolar {11-22}, {10-11}, and {20-21} GaN layers on PSSs using HVPE [25].…”