Materials Department, University of California, Santa Barbara, California 93106-5050, USA.
J Chem Phys. 2011 Feb 28;134(8):084703. doi: 10.1063/1.3548872.
Band gaps and band alignments for AlN, GaN, InN, and InGaN alloys are investigated using density functional theory with the with the Heyd-Scuseria-Ernzerhof {HSE06 [J. Heyd, G. E. Scuseria, and M. Ernzerhof, J. Chem. Phys. 134, 8207 (2003); 124, 219906 (2006)]} XC functional. The band gap of InGaN alloys as a function of In content is calculated and a strong bowing at low In content is found, described by bowing parameters 2.29 eV at 6.25% and 1.79 eV at 12.5%, indicating the band gap cannot be described by a single composition-independent bowing parameter. Valence-band maxima (VBM) and conduction-band minima (CBM) are aligned by combining bulk calculations with surface calculations for nonpolar surfaces. The influence of surface termination [(1100) m-plane or (1120) a-plane] is thoroughly investigated. We find that for the relaxed surfaces of the binary nitrides the difference in electron affinities between m- and a-plane is less than 0.1 eV. The absolute electron affinities are found to strongly depend on the choice of XC functional. However, we find that relative alignments are less sensitive to the choice of XC functional. In particular, we find that relative alignments may be calculated based on Perdew-Becke-Ernzerhof [J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 134, 3865 (1996)] surface calculations with the HSE06 lattice parameters. For InGaN we find that the VBM is a linear function of In content and that the majority of the band-gap bowing is located in the CBM. Based on the calculated electron affinities we predict that InGaN will be suited for water splitting up to 50% In content.
采用密度泛函理论（DFT）结合 Heydd-Scuseria-Ernzerhof（HSE06）[J. Heyd、G. E. Scuseria 和 M. Ernzerhof，J. Chem. Phys. 134，8207（2003）；124，219906（2006）] XC 泛函研究了 AlN、GaN、InN 和 InGaN 合金的能带隙和能带排列。计算了 InGaN 合金中随 In 含量变化的能带隙，并发现了在低 In 含量下的强烈翘曲，由 6.25%时的 2.29 eV 和 12.5%时的 1.79 eV 的翘曲参数来描述，表明能带隙不能用单个成分独立的翘曲参数来描述。价带最大值（VBM）和导带最小值（CBM）通过结合体相计算和非极性表面的表面计算来对齐。彻底研究了表面终止（[1100] m 平面或[1120] a 平面）的影响。我们发现，对于二元氮化物的弛豫表面，m 平面和 a 平面之间的电子亲和能差小于 0.1 eV。绝对电子亲合能强烈依赖于 XC 泛函的选择。然而，我们发现相对对齐对 XC 泛函的选择不太敏感。特别是，我们发现相对对齐可以基于 Perdew-Becke-Ernzerhof[J. P. Perdew、K. Burke 和 M. Ernzerhof，Phys. Rev. Lett. 134，3865（1996）]的表面计算和 HSE06 晶格参数来计算。对于 InGaN，我们发现 VBM 是 In 含量的线性函数，并且大部分能带隙翘曲位于 CBM 中。基于计算出的电子亲合能，我们预测 InGaN 将适用于高达 50% In 含量的水分解。
