A Theoretical Investigation of the Miscibility and Structural Properties of In_xAl_yGa_1−x−yN Alloys

Abstract

In this theoretical investigation of the miscibility in quaternary alloys, we stay in the regular solution model and determine the interaction parameters from the enthalpy of mixing calculated using a modified Stillinger–Weber (SW) potential for III‐nitride ternary alloys. From our calculation, the values of the interaction parameters are 6.605, 10.523, and 0.677 kcal mol−1, respectively, for InGaN, InAlN, and AlGaN at x = 0.5 (where x is the In and Al fraction in InGaN, InAlN, and AlGaN, respectively). These values are in good agreement with those predicted by the improved delta lattice parameter (DLP) model for nitride ternary alloys. To determine the unstable regions characterized by the spinodal decomposition of the quaternary alloy InxAlyGa1−x−yN, we consider the composition ranges of 0.06 ≤ x ≤ 1 and 0 ≤ y ≤ 0.94. Our calculations show that the phase separation temperature increases with the increase of indium concentration. For In concentration lower than 9.4%, the quaternary alloy is miscible independent of the Al and Ga compositions in the usual growth temperature range for metalorganic vapor phase epitaxy.

Self-Induced Core–Shell InAlN Nanorods: Formation and Stability Unraveled by Ab Initio Simulations

“…35 Geometric relaxation of the NR model systems (Figure 2a,b) was followed by evaluation of their electronic states as well as by performance of the corresponding population analysis thus determining their band gaps (Table 2). The analysis of the band gap dependence on the In concentration in the NR core is considered informative not only because of potential applications but also due to the well-known wide miscibility gap observed in the AlN−InN system and related spinodal decomposition, 36 which may manifest itself as significant variations of the band gap values of the considered model systems at their relaxations.…”

The critical role of N-vacancy on chemical composition fluctuations and degradation of InAlN layer

“…During last years, numerous modelling works have also been devoted to phase diagrams in ternary and quaternary solid solutions [26][27][28][29][30] to determine the instability zone in this alloy; more recently, we demonstrated that biaxial strain influences its miscibility zone 29 . However, structural defects (hillocks and V-defects) were observed independent of the type of strain in InAlN layers for low In compositions of 13.5% (tensile strain), as well as at 19.7% (compressive strain), suggesting that their origin may not be related only to the strain state, but to the intrinsic properties of the InAlN alloy.…”

Indium segregation mechanism and V-defect formation at the [0001] InAlN surface: an ab-initio investigation

“…However, the growth of high quality InAlN films with 18% In content, as needed to avoid the formation of extended crystallographic defects [5], has proved challenging. The size difference between Al and In, in addition to that of Al-N and In-N bond strengths may limit the homogeneous growth leading to theoretically reported spinodal decomposition and phase separation [6,7].…”

“…However, the growth of high quality InAlN films with 18% In content, as needed to avoid the formation of extended crystallographic defects [5], has proved challenging. The size difference between Al and In, in addition to that of Al-N and In-N bond strengths, may limit the homogeneous growth leading to theoretically reported spinodal decomposition and phase separation [6,7]. Furthermore, InN is the least stable among the III-nitride semiconductors, with thermal decomposition starting at temperatures as low as 470 • C [8]; this is low compared to that required for the growth of best quality AlN (∼1600 • C) [9].…”