Optical and structural properties of dislocations in InGaN

Abstract

Threading dislocations in thick layers of InxGa1-xN (5% < x < 15%) have been investigated by means of cathodoluminescence, time-resolved cathodoluminescence and molecular dynamics. We show that indium atoms segregate near dislocations in all the samples. This promotes the formation of InN In chains and atomic condensates which localize carriers and hinder non-radiative recombination at dislocations. We note however that the dark halo surrounding the dislocations in the cathodoluminescence image becomes increasingly pronounced as the indium fraction of the sample increases. Using transmission electron microscopy, we attribute the dark halo to a region of lower indium content formed below the facet of the V-shaped pit that terminates the dislocation in low composition samples (x < 12%). For x > 12%, the facets of the V-defect featured dislocation bundles instead of the low indium fraction region. In this sample the origin of the dark halo may relate to a compound effect of the dislocation bundles, of a variation of surface potential and perhaps of an increase in carrier diffusion length.

Strongly reduced V pit density on InGaNOS substrate by using InGaN/GaN superlattice

“…However, a deeper study has to be done to understand the origin of the supplementary V pits, and especially if they are initiated from some of these pinhole like defects. The surface morphology is changed from hillocks (spiral growth) on InGaNOS substrate to step meandering growth mode after overgrowth of the simple InxGa1-xN buffer layer [29]. Compared to the InGaNOS-3.205 surface to that of the buffer layer, the averaged V pit diameter increases from 80 nm to 160 nm, respectively.…”

“…When enough compressive strain has been stored by the system, six sidewall facets are created to release strain [26]. It happens usually at a dislocation core where tensile strain is present so that In atoms accumulate in this area and form In-N-In chains [29], which, in addition, act as localization centres to prevent carriers from being wasted in non radiative recombination processes [29]. Furthermore, V pit density and V pit diameter increase with the InxGa1-xN layer thickness [28].…”

Multicolor Emission from Ultraviolet GaN-Based Photonic Quasicrystal Nanopyramid Structure with Semipolar InxGa1−xN/GaN Multiple Quantum Wells

“…4a. The slight broad spectrum from the sample B was attributed to the existence of defects and dislocations generated by the higher indium composition [56][57][58].…”

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

“…The high density trench defects depend on various parameters such as the InGaN thickness, In composition, GaN buffer layer thickness, and miscut of sapphire substrate. In the past literature, F.P.Massabuau and related coworkers investigated the effect of trench defects on InGaN QWs and InGaN layers [17,22,26,[28][29][30]. These studies mainly accessed the resulting of structural and optical properties.…”