Role of Nanoscale Strain Inhomogeneity on the Light Emission from InGaN Epilayers

Abstract

InGaN is the basis of a new generation of light‐emitting devices, with enormous technological potential; it is currently one of the most intensively studied semiconductor materials. It is generally accepted that compositional fluctuations resulting from phase segregation are the origin of the high luminescence efficiency of InGaN. Evidence to show that nanoscale strain inhomogeneity plays a fundamental role in determining the spectral properties of InGaN–GaN heterostructures is reported. For layers above a certain critical thickness, a strong spatially varying strain profile accompanies a nonplanar surface morphology, which is associated with a transition from a planar 2D to a Stranski–Krastanow‐like 2D–3D growth mode; the strong dependence of the critical thickness on the local InN content of the growing films drives a non‐linear growth instability. Within this framework, apparently disparate experimental observations regarding structural and optical properties, previously reported for InGaN layers, are reconciled by a simple phenomenological description.

Anisotropically biaxial strain in non-polar (112–0) plane In x Ga1−x N/GaN layers investigated by X-ray reciprocal space mapping

“…4 suggest different relaxations state, the multi-peak pattern cannot be explained with phase separation. Therefore, we speculate the multi-peak phenomenon is a result of the strain relaxation process, which is also observed by other groups 19 – 22 . As the growth proceeds, the InGaN-1 layer with x In ~ 0.09 is initially coherently grown on the smooth GaN template, similar to the case of the layer in Fig.…”

Role of compositional fluctuations and their suppression on the strain and luminescence of InGaN alloys

“…A similar conclusion was drawn in Ref. 43. The study presented therein is based on XRD and AFM measurements on a macroscopic level, highlighting again that the findings from the microscopic analysis presented here accurately reflects macroscopic properties of InGaN epilayers.…”

Nanometer-scale, quantitative composition mappings of InGaN layers from a combination of scanning transmission electron microscopy and energy dispersive x-ray spectroscopy

“…The second diffraction spot corresponds to a fully relaxed 20% InGaN layer. Similar results have been observed for thick InGaN layers in [22][23][24][25][26][27][28][29].…”