Tunable optoelectronic and ferroelectric properties in Sc-based III-nitrides
Tunable optoelectronic and ferroelectric properties in Sc-based III-nitrides
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DOI：
10.1063/1.4824179
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发表时间：
2013-03
影响因子：
3.2
通讯作者：
Siyuan Zhang;D. Holec;W. Fu;C. Humphreys;M. Moram
中科院分区：
文献类型：
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作者：
Siyuan Zhang;D. Holec;W. Fu;C. Humphreys;M. Moram
采用密度泛函理论和特殊的准随机结构方法对钪基III族氮化物合金进行了研究。发现ScxAl 1 −xN和ScxGa 1 −xN合金分别在x ≤ 0.56和x ≤ 0.66的六方相中是稳定的，在此之上岩盐结构更稳定。外延应变稳定化可以防止亚稳分解高达x ≤ 0.4（AlN或GaN上的ScxAl 1 −xN）和x = 0.27（GaN上的ScxGa 1 −xN）。Sc含量的增加扩大了ScxAl 1 −xN和ScxGa 1 −xN合金的面内晶格参数，导致成分和应变可调的带隙和极化，并最终在x = 0.625时在ScxGa 1 −xN中引入铁电功能。一个修改后的Becke-Johnson交换相关势被应用到研究的电子结构，产生的带隙可比的混合功能计算，但在一个更短的计算时间。合金被发现保持宽带隙，保持直接高达x = 0.25（ScxAl 1 −xN）和x = 0.5（ScxGa 1 −x）。
Sc-based III-nitride alloys were studied using density functional theory with special quasi-random structure methodology. ScxAl1−xN and ScxGa1−xN alloys are found to be stable in hexagonal phases up to x ≈ 0.56 and x ≈ 0.66, respectively, above which rock-salt structures are more stable. Epitaxial strain stabilization can prevent spinodal decomposition up to x ≈ 0.4 (ScxAl1−xN on AlN or GaN) and x = 0.27 (ScxGa1−xN on GaN). The increase in Sc content expands the in-plane lattice parameter of ScxAl1−xN and ScxGa1−xN alloys, leads to composition- and strain-tunable band gaps and polarization, and ultimately introduces ferroelectric functionality in ScxGa1−xN at x ≈ 0.625. A modified Becke-Johnson exchange-correlation potential was applied to study the electronic structures, which yielded band gaps comparable to those from hybrid functional calculations, yet in a much shorter computational time. The alloys were found to retain wide band gaps, which stay direct up to x = 0.25 (ScxAl1−xN) and x = 0.5 (ScxGa1−x...