In the semipolar and nonpolar growths, - c-plane growth promoted the generation of stacking faults. The InGaN growth occurred on both the sidewalls of the InGaN template, in a manner similar to the growth on the patterned GaN template. At the initial growth stage, there was no nucleation on the SiO 2 mask on the InGaN template. Epitaxial Lateral Overgrowth of InGaN on the GaN Templateįigure 6 shows the cross-sectional and plan-view SEM images of the InGaN layers at the initial stage of growth and after coalescence. Thus, to maintain the quality of the InGaN layers and high migration of Ga, the ELO of InGaN was carried out at In contents of less than 6% in this study. We also carried out the ELO of InGaN with an In content greater than 10% however, we did not succeed in growing a smooth InGaN layer. However, a high density of misfit dislocations was generated in the InGaN layers prepared with high In content. When the In content was low, few misfit dislocations existed at the interface between InGaN and GaN, and they did not form threading dislocations. We have previously analyzed these samples by transmission electron microscopy (TEM). The InGaN layers prepared with the In content of less than 18% exhibited a smooth surface. The optimization of InGaN growth was not performed. The In content was determined from the XRD results according to Vegard’s law, and the relationship between the In content and growth temperature is shown in Figure 2. The RMS results showed that all of the samples grew fully relaxed.
This is because a very rough surface with a high dislocation density, consisting of InGaN differ from those of GaN. Furthermore, from the viewpoint of the fabrication of high-quality InGaN layers grown on GaN, the c-plane is not suitable. However, the crystalline quality of the InGaN layers currently produced is insufficient for the above purpose. In addition, the relaxation effects of InGaN and pseudomorphic InGaN layers have been reported. For this reason, the fabrication of thick c-plane InGaN layers has been of considerable interest. One of the most promising routes for realizing high-efficiency, longer-wavelength LEDs and LDs based on InGaN is the use of a thick underlying layer composed of an InGaN ternary alloy with a low defect density that can reduce the lattice mismatch between the template and active layer. However, the major factors that prevent the realization of high-performance devices are the large internal electric field and the generation of misfit dislocations caused by the large lattice mismatch between the GaN template and InGaN active layer. InGaN-based multiple quantum wells (MQWs) are typically used as an active layer in such devices and are grown on a thick GaN template layer or a GaN substrate. In particular, GaN-based LEDs have attracted increasing attention as promising materials for optoelectronic device applications. There has also been an increasing demand for laser diodes (LDs) with longer emission wavelengths. The EQEs of LEDs with different wavelengths in the visible light region (from purple to red) have been improved, with record efficiencies being reported. Light-emitting diodes (LEDs) with very high external quantum efficiencies (EQEs) have been developed based on advancements in LED fabrication technologies.
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