Raman scattering of indium-richAlxIn1−xN: Unexpected two-mode behavior of

Abstract

Al x In 1−x N films ͑0.03Յ x Յ 0.80͒, particularly indium-rich AlInN films, are studied by Raman scattering. We clearly observe a two-mode behavior of A 1 ͑LO͒ phonon and prove that the previous theoretical prediction and experimental attribution of InN-like A 1 ͑LO͒ to E 2 H mode are incorrect. Using the modified random-element isodisplacement model of Chang and Mitra, the information about AlInN lattice vibration is extracted. We believe that these results imply a strong positive force interaction between In and Al sublattices in AlInN. The strong interaction makes AlInN different with AlGaN in A 1 ͑LO͒ phonon mode behavior.The lattice dynamics of random alloys is a complex issue. The complexity results from the interplay of different lattice bonds due to composition variation. An important phenomenon in this field is the mode behavior of long-wavelength optical phonons. It is known that ternary mixed crystals A x B 1−x C with fully pronounced random alloy character are classified into two main classes according to the behavior of zone-center optical phonons. In the one-mode class, the frequencies vary continuously and approximately linearly with the molar fraction x of the alloy. In the case of two-mode behavior, there are two sets of optical modes corresponding nearly to those of two pure crystals AC or BC which compose the alloy. These extra modes may persist very close to the end compositions, i.e., x = 0 and x =1. 1 In order to determine the mode behavior of longwavelength optical phonons in mixed crystals, using the modified random-element isodisplacement ͑MREI͒ model, Chang and Mitra 2 deduced their criteria in 1968. These criteria are for A x B 1−x C, m A , m B , m C are the atomic masses of atoms A, B, and C, and m A Ͻ m B . If m A Ͻ BC ͓ BC = m B m C / ͑m B + m C ͒ is the reduced mass of atoms B and C͔, it exhibits two-mode behavior; whereas the opposite is true for the one-mode behavior. These criteria succeed in interpreting many experimental results, such as the two-mode behavior for longitudinal optical ͑LO͒ phonons in AlGaAs ͑Ref. 3͒ and AlInAs ͑Ref. 4͒ and the one-mode behavior for A 1 ͑LO͒ in hexagonal MgZnO. 5 For III-nitride alloys, the most extensively studied one is AlGaN. Raman scattering has shown that E 2 H phonon shows two-mode behavior and A 1 ͑LO͒ shows one-mode behavior. 6 The one-mode behavior for longitudinal phonons A 1 ͑LO͒ is in good agreement with the one-mode criteria of Chang and Mitra, 2 i.e., m Al Ͼ GaN , because of the much smaller mass of nitrogen atom than Al and Ga atom. Those observations have stimulated a lot of theoretical research to interpret the experimental results of AlGaN and predict the future results of other III-nitride alloy, including AlInN, for which one-mode criteria m Al Ͼ InN are still satisfied well. They have usually adopted various versions of MREI model as theoretical basis. 7,8 For example, Grille et al. 7 predicted that for AlInN, A 1 ͑LO͒ also exhibits one-mode behavior and E 2 H exhibits two-mode behavior.Naik et al. 9 used Raman scattering ...

Effect of gas flow on the growth of In-rich AlInN films by metal-organic chemical vapor deposition

“…This identification is also supported by comparing the Raman spectra shapes here and those in Ref. 13.…”

“…Raman spectra are measured on the AlInN surface in a backscattering configuration at room temperature with 514 nm laser excitation. Before this paper, we have given a strong experimental support to the two-mode behavior for A 1 ͑LO͒ phonon in AlInN, 13 which is in contrast with previously widely adopted one-mode A 1 ͑LO͒ phonon behavior. 14 Fig.…”

Type-I band alignment at MoS2/In0.15Al0.85N lattice matched heterojunction and realization of MoS2 quantum well

“…1(d) ,N) , where m is the mass and l is the reduced mass. 31,32 In contrast, the phonon modes of In 0.15 Al 0.85 N were not observed when the sample was excited with the 473 nm line, as shown in Fig. 1(d) (ii and iii), which is ascribed to the reduced resonant excitation effect.…”

Temperature dependence of Raman scattering in AlInN

“…[3][4][5] In order to fulfill AlInN applications in commercially optical and electronic devices, the fundamental properties of this material have been studied experimentally [1][2][3][4][5][6][7][8][9][10][11] and theoretically. [12][13][14] Starosta 11 has reported the first synthesis of AlInN polycrystalline films by a reactive multitarget sputtering method. Subsequently, there have been numerous reports about the growth of single phase AlInN by a variety of methods, 1,3,5,7 with the emphasis on improving the quality, due to the large differences in chemical and physical parameters between InN and AlN.…”