Resonant Raman Scattering in GaN/Al_0.15 Ga_0.85N and In_yGa_1-yN/GaN/Al_xGa_1-xN Heterostructures

Abstract

We report on resonant Raman scattering in Al0.15Ga0.85N/GaN single quantum wells (QWs) and AlxGa1-xN/GaN/lnyGa1-yN heterostructures. By choosing appropriate excitation conditions we could probe selectively the GaN quantum well or the Al0.15Ga0.85N barrier of Al0.15Ga0.85N/GaN single quantum wells. For the InxGa1-xN material system a linear frequency shift of the E2- and A1(LO) phonon mode to lower frequencies was found with increasing In content. The shift was determined to -0.79cm-1 per % In content for the A,(LO) phonon frequency. Resonant excitation of AlxGa1-xN/GaN/InyGa1-YN heterostructures enabled us to detect phonon signals from the InxGa1-xN layer in the heterostructure and to determine its In content.

Raman phonon modes of zinc blende InxGa1−xN alloy epitaxial layers

“…12 The A 1 ͑LO͒ and E 2 phonon frequencies of the h-In x Ga 1Ϫx N alloy with an In content varying between 1.9% and 11.3% were measured by Raman spectroscopy. 13 The LO phonon frequencies measured by us are fairly consistent with these reported data. Based on early infrared reflectivity experiments on hIn x Ga 1Ϫx N polycrystalline films 14 and recent Raman data for the c-InN and c-GaN binary compounds 15,16 we use our results to predict the A 1 ͑TO͒ and E 1 ͑TO͒ phonon frequencies of the hexagonal alloy.…”

Evidence for compositional inhomogeneity in low In content (InGa)N obtained by resonant Raman scattering

“…Raman data on the composition dependence of the longitudinal optical A 1 ͓A 1 (LO)͔ phonon and the high-frequency E 2 phonon mode in ͑InGa͒N, as well as preliminary results on resonance effects in Raman scattering by the A 1 (LO) phonon, have been reported in Ref. 10.…”

Indium Distribution within InxGa1?xN Epitaxial Layers: A Combined Resonant Raman Scattering and Rutherford Backscattering Study

“…This would be expected while the lattice mismatch is accommodated by the elastic strain. A totally different conclusion would be taken if the expression for w relax (x) established by D. Behr et al [6] was used. In this case, larger values of x would correspond to more relaxed regions.…”

“…For the case of the In x Ga 1--x N alloy, it has been theoretically [2] and experimentally [3][4][5][6] demonstrated that it shows one-mode behavior, i.e. exhibits only one set of longitudinal optical (LO) and transverse optical (TO) phonons, whose frequencies vary almost linearly with compositional changes.…”

“…exhibits only one set of longitudinal optical (LO) and transverse optical (TO) phonons, whose frequencies vary almost linearly with compositional changes. Due to the lack of good quality samples for a wide range of composition, the A 1 (LO) phonon frequency dependence on the indium content x is not yet well-established and different behaviors can be found in the literature [4][5][6]. In some cases the observed asymmetrical band shape leads to an uncertainty on the phonon frequency at the Brillouin center zone.…”