InGaN quantum dot growth in the limits of Stranski–Krastanov and spinodal decomposition

Abstract

Most commonly used for the self-assembling of InGaN quantum dots is a Stranski-Krastanov growth scheme. Often neglected is the influence of spinodal decomposition, although it is frequently discussed with quantum well growth. In this publication we will expose the influence of both mechanisms on the formation process of quantum dots. This paper gives an insight in the theoretical background of quantum dot formation and covers the growth by molecular beam epitaxy and metal organic vapor phase epitaxy. Stranski-Krastanov like growth has been verified by the surface evolution beyond the critical thickness as seen by atomic force microscopy on uncapped samples. The overgrowth of such samples led to dissolution of the quantum dots. Indium compositions within the miscibility gap below critical thickness yielded spinodal phase separation in meander like structures These structures are in agreement with the theory from Hilliard and Cahn. Based on spinodal decomposition overgrowth schemes have been developed which showed reliable quantum dot emission. Such layers have been implemented into device structures such as LEDs and laser structures.

An XANES and XES investigation of the electronic structure of indium rich InxGa1−xN films

“…Bimodal and spinodal decomposition occurs and the ternary compounds remain stable only for In-contents less than 20% or greater than 80% [2]. This instability range has been also shown to depend upon the strain state of the epitaxial layers [3]. In order to gain more knowledge about this range, the study of In x Ga 1−x N layers with a high In content were performed.…”

Effects of matrix layer composition on the structural and optical properties of self-organized InGaN quantum dots

“…2(b), the typical QD has a truncated pyramidal shape, which is a common structure of MOCVD grown self-assembled InGaN QDs. 10,11 To investigate the influence of matrix layer on the structural and optical properties of InGaN QDs, In 0.1 Ga 0.9 N and GaN matrix layers were utilized in group I samples and group II samples, respectively. Figure 3 shows the schematic layer structures of these two groups of samples.…”

Characterization of InGaN/GaN quantum well growth using monochromated valence electron energy loss spectroscopy

“…25,26 Here, a pseudomorphic growth was observed, hence no misfit dislocations are present to reduce the strain under the QDs. Typically, this is only possible by increasing the strain energy of the underlying substrate, 27 resulting in a redshift of E p of the underlying substrate. Indeed, such an apparent shift of the well onset is subtly observed under the QDs (Figure 8(d)).…”