Indium Incorporation Induced Morphological Evolution and Strain Relaxation of High Indium Content InGaN Epilayers Grown by Metal–Organic Chemical Vapor Deposition

Abstract

The indium (In) incorporation induced morphological evolution and strain relaxation of high In content InGaN epilayers grown by metal–organic chemical vapor deposition (MOCVD) were investigated. With the decrease of growth temperature from 753 to 627 °C, In incorporation increases from 0.10 to 0.42, and the surface morphology evolves from initially mound-like three-dimensional surface roughness to progressive smoothness. Such morphology evolution mechanism can be well accounted for by a self-regulating model of islands’ proportions considering both strain relaxation and In surfactant effect comprehensively. Additionally, the strain relaxation and microstructural defects of such InGaN epilayers were investigated by X-ray diffraction reciprocal space mapping and cross-sectional transmission electron microscopy, respectively. It is found that, with the increase of In content, plastic relaxation via generating random stacking faults along with the surface sawtooth roughening becomes a more important strain relaxation mechanism. The presented results contribute to better understanding of the microscopic nature and growth mechanisms of high In content InGaN epilayers grown by MOCVD.

Effects of indium flow rate on the structural, morphological, optical and electrical properties of InGaN layers grown by metal organic chemical vapour deposition

“…Particularly in sample B, the V-defects density dramatically decreases and trench defects density increases concomitantly. A rather high crack like defects was also observed while compared to the other two samples [24,26,48]. These kinds of crack like defects were certainly to mediate the high density trench defects from the similar factors observed in literature [49].…”

“…It was also observed that, the distribution of 3D island was without obvious flat zones on the surface. In this phenomenon, while increasing the Indium flow rate, more indium incorporation occurred which results in increasing the misfit strain in the layer, this accelerate the formation of 3D islands [24]. Figure 6 clearly shows that there is a random change in the surface morphology of InGaN samples grown by MOCVD.…”

“…Upon Increasing the In composition in InGaN layers the contour shapes in the RSM are found to be irregularly broadened along the Qx and Qy directions with respect to the GaN layer which is attributed to the mosaic structure of the layers. Here the percentage of strain relaxation (R) and defined as [24], 100…”

“…This spectacle of the InGaN based structures is correlated to the lattice relaxation during the growth process. Although, it lacks the morphological, strain relaxation and longer wavelength (green to red) emission of indium incorporation for InGaN alloys by MOCVD [23,24]. In this case, the trench defects surrounded InGaN layers are most likely to emit the green spectrum and it may play a deleterious role to the degradation of quality compared to blue spectrum [22,25].…”

“…The luminescence properties of the InGaN samples were understood by the fluctuations in the In composition and red shift of the emissions with respect to the formation of V and trench defect.The hall measurements of the InGaN/GaN heterostructures shows more alloy scattering centers and also reveals alteration in the semiconductor behavior with respect to V and trench defect surrounded InGaN layers. From the obtained results, it gives an additional comprehension of the scientific information of the present in respect of the structural (crystalline quality, composition, layer thickness, lattice constants, strain parameters and reciprocal space mapping), morphological (features of V & trench defect, roughness and related width, depth density), luminescence (emissions of three different points-PF, Centre, Edge) and electrical (mobility, bulk &sheet concentration and related scattering mechanism) properties of InGaN layers were studied compare to the other studies[24,26,60]. These kinds of results help further to development of next generation optoelectronics devices (longer wavelength light emitting diodes etc) based on V and trench defects surrounded InGaN layers.…”