Structural perfection of InGaN layers and its relation to photoluminescence

Abstract

The relation between structural perfection and optical properties of InGaN with 10% In are discussed. Transmission Electron Microscopy, X‐ray diffraction and Rutherford backscattering spectrometry measurements show that only strained layers with a thickness not exceeding 100 nm are defect free and In concentration is lower than the nominal value. Extension of layer thickness leads to layer sequestration into sublayers with different In contents and the formation of planar defects as a result of layer relaxation. In concentration in such sublayers reach and in some cases exceed the nominal concentration. A single band edge photoluminescence peak is observed only for the thinnest layer. Samples with larger film thickness showed multiple PL peaks corresponding to layers with different In content. Much higher In content would be required to explain the presence of some PL peaks, suggesting that some PL peaks originate from the defective areas of the film. This was confirmed by cathodoluminescence studies performed on the same samples used earlier for TEM studies. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Remarkable enhancement in photocurrent of In0.20Ga0.80N photoanode by using an electrochemical surface treatment

“…Generally, a thicker thin film will lead to division of layer into sublayers with different In contents. [13][14][15] The thick In x Ga 1Àx N film consists of three different structural phase: an In-rich InGaN region on the surface, a region free from the In-rich InGaN phase in the middle, and an InGaN/GaN interface region on the bottom of the film. 16 Herein, we found the In-rich InGaN layer had a negative effect on photocurrent of In 0.20 Ga 0.80 N electrode due to surface recombination.…”

Structural defects and cathodoluminescence of InxGa1‐xN layers

“…Recently we also demonstrated that structural perfection of InGaN changes with the layer thickness even for nominal In concentrations as small as 10% [3]. A nearly defect free, strained layer at the interface and a relaxed, defective layer with a high density of structural defects and surface corrugation are observed.…”

“…A JEOL 3010 with 300 keV accelerating voltage and a resolution of 2.4 Å, JEOL CM300 with sub-Angstrom resolution and TEAM 0.5 for HAADF Zcontrast STEM high resolution studies have been used. 3 Results and discussion Our earlier studies using XRD [3] showed a sharp intense GaN peak and a broad InGaN peak which started to split for layers thicker than 200 nm. This resulted from the formation of sub-layers with different c parameters, indicating the onset of relaxation in the InGaN layer and different Indium concentration in the sub-layers.…”

Impact of metalorganic vapor phase epitaxy growth conditions on compressive strain relaxation in polar III-nitride heterostructures

“…Symbols in Fig. 3 show the experimental data on CT collected earlier [24][25][26][27][28][29][30][31][32] and borrowed additionally from Ref. 33.…”