Compositional dependence of the strain-free optical band gap in InxGa1−xN layers

Abstract

The effect of strain on the compositional and optical properties of a set of epitaxial single layers of In x Ga 1Ϫx N was studied. Indium content was measured free from the effects of strain by Rutherford backscattering spectrometry. Accurate knowledge of the In mole fraction, combined with x-ray diffraction measurements, allows perpendicular strain (⑀ zz ) to be evaluated. Optical band gaps were determined by absorption spectroscopy and corrected for strain. Following this approach, the strain free dependence of the optical band gap in In x Ga 1Ϫx N alloys was determined for xр0.25. Our results indicate an ''anomalous,'' linear, dependence of the energy gap on the In content, at room temperature: E g (x)ϭ3.39-3.57x eV. Extension of this behavior to higher concentrations is discussed on the basis of reported results.

Hybrid functional investigations of band gaps and band alignments for AlN, GaN, InN, and InGaN

“…The various experimental [45][46][47][48][49][50][51][52][53] as well as theoretical [54][55][56][57][58][59][60][61][62][63][64] studies have disagreed on the magnitude of the bowing parameter.…”

“…For ternary nitride alloys, such as InGaN, consensus on the band gap as a function of composition has not been reached. A number of studies have measured the band gap as a function of In content, [45][46][47][48][49][50][51][52][53] resulting in a large spread in reported band gaps. Qualitatively, there is agreement that the band gap of InGaN is a nonlinear function of alloy composition.…”

Reduced thermal quenching in indium-rich self-organized InGaN/GaN quantum dots

“…The thin WL and the QDs are assumed to be pseudomorphically grown (a InGaN ¼ a GaN ) and thus the indium content within the structures can be estimated by solving Hooke's law, 6,7 ½c InGaN À c 0 þ 2 C 13 ðxÞc 0 ðxÞ C 33 ðxÞa 0 ðxÞ ½a InGaN À a 0 ¼ 0; where c 0 and a 0 are the relaxed lattice constants and C 13 and C 33 are the stiffness coefficients of the InGaN structures. The downside of this technique is the underestimation of the indium content due to the crystal's partial relaxation.…”

Response to “Comment on ‘Direct evidence of nanocluster-induced luminescence in InGaN epifilms’ ” [Appl. Phys. Lett. 87, 136101 (2005)]

“…The comments over emphasized the role played by strain as also shown in their previous reports. 14,15 We believe that it is reasonable to interpret our results based on the fact of the existence of nanometer-scale clusters in InGaN films.…”