Modeling the compositional instability in wurtziteGa1−xInxN

Abstract

The paper deals with multiscale modeling of the minor component ordering in wurtzite Ga 1−x In x N ͑x Ͻ 0.5͒ alloys. The treatment combines the total-energy density-functional calculations of the metal atom interaction parameters and the atomistic description of the alloy decomposition using lattice kinetic Monte Carlo. It is demonstrated that the phase decomposition patterns in wurzite GaInN are very sensitive to the interplay of metal atom interactions at several interatomic distances ͑at least to the fourth nearest neighbors͒ on the cation sublattice. Variation of the metal interaction energies within reasonable limits resulted in pronouncedly different relaxation patterns ͑linear or wall ordering of In and Ga atoms along c-axis, planar ordering parallel to basal plane, spinodal decomposition͒. The high sensitivity of the GaInN decomposition to relatively small variations of the metal interaction energies could be the main reason for the experimentally observed versatility of the alloy decomposition patterns and their sensitivity to the particular experimental conditions.

Distribution of cations in wurtzitic InxGa1−xN and InxCarvalho1, Schleife2, Furthmüller3 et al. 2012Phys. Rev. B251180View full textAdd to dashboardCite

“…19 The possible instability of In x X 1−x N layers (X=Ga, Al) against decomposition into two random alloys as well as the occurrence of fluctuations in a compositionally disordered system have been studied theoretically in a variety of papers. 10,[20][21][22][23][24][25][26] Many of these studies [20][21][22] consistently predict a miscibility gap for In x Ga 1−x N (mainly for the zinc-blende structure) in a broad temperature range and, hence, explain observations of precipitation or even spinodal decomposition. 27 More recently, minor component ordering and clustering in wz-In x Ga 1−x N but also wz-In x Al 1−x N has been studied by means of multiscale or ab initio methods.…”

“…27 More recently, minor component ordering and clustering in wz-In x Ga 1−x N but also wz-In x Al 1−x N has been studied by means of multiscale or ab initio methods. [23][24][25] Nevertheless, it has been found experimentally that the incorporation of small amounts of In leads to an enhancement of the light emission intensity in light-emitting diodes as well as laser diodes with respect to devices made from pure GaN or AlN. 28 This may be related to In clustering as well as composition fluctuations.…”

Ordering in ternary nitride semiconducting alloys

“…There are also kinetic studies available in the literature for nitrides. 18 The energetics in our calculations is computed on the basis of the Keating valence force field model and, for the sake of simplicity, we focus on the zinc-blende structures. The studies are carried out in the lattice-coherent thermodynamics regime, i.e., we assume that the alloy constituents form common lattice and can not decay into separate components, each with its own independent lattice parameter.…”

Indium distribution and light emission in wurtzite InGaN alloys: Several-atom In-N clusters

“…The previously observed In-rich QDs-like are created by electron beam damage [11,20]. A careful low-dose electron microscopy reveals no In-rich QDslike, but it cannot rule out small In fluctuations in In x Ga 1−x N. The recent many works on successful synthesization of high quality phase-separation-free In x Ga 1−x N based microstructures, such as high quality In x Ga 1−x N films [21], In x Ga 1−x N/GaN multiple QW solar cells [22] and In x Ga 1−x N (0 x 1) nanowires [23], together with some theoretical investigations in exploring the In-atom distribution or In clustering [24][25][26][27], clearly indicate that it is still an open question under dispute whether In x Ga 1−x N forms uniform alloy or has obvious phase separation or small In content fluctuations. One of our purposes here is to outline the real crystal structure of In x Ga 1−x N (0 x 1) alloys and seek the In-related special microstructures associated with the elusive electron localization centers based on minimization of the total energy.…”