Tsai Yi-Chia, Bayram Can
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States.
Nick Holonyak, Jr Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States.
ACS Omega. 2020 Jan 30;5(8):3917-3923. doi: 10.1021/acsomega.9b03353. eCollection 2020 Mar 3.
Band gaps and electron affinities of binary and ternary, wurtzite (wz-) and zincblende (zb-) III-nitrides are investigated using a unified hybrid density functional theory, and band offsets between wz- and zb- alloys are calculated using Anderson's electron affinity model. A conduction (and valence) band offset of 1.85 (0.89) eV has been calculated for zb-GaN/InN heterojunctions, which is 0.25 eV larger (and 0.26 eV smaller) than that of the wz- counterpart. Such polarization-free zb-GaN/InGaN/GaN quantum well structures with large conduction band offsets have the potential to suppress electron leakage current and quantum-confined Stark effects (QCSEs). Contrarily, the conduction (and valence) band offset of zb-AlN/GaN heterojunctions is calculated to be 1.32 (0.43) eV, which is 1.15 eV smaller (and 0.13 eV larger) than that of the wz- case. The significant reduction in zb-AlN/GaN band offsets is ascribed to the smaller and indirect band gap of zb-AlN-the direct-to-indirect crossover point in zb-Al Ga N is when ∼ 65%. The small band gap of the zb-AlN barrier and the small conduction band offsets imply that electrons can be injected into zb-AlN/GaN/AlN quantum well heterostructures with small bias and less energy loss when captured by the quantum wells, respectively, i.e., loss as heat is reduced. The band gap of ternary III-nitrides does not linearly depend on alloy compositions, implying a nonlinear dependence of band offsets on compositions. As a result, the large bowing of the conduction band offset is identified and ascribed to the cation-like behavior of the conduction band minimum, while the linear dependence of the valence band offset on compositions is attributed to the anion-like character of the valence band maximum.
使用统一的杂化密度泛函理论研究了二元和三元纤锌矿（wz-）和闪锌矿（zb-）III族氮化物的带隙和电子亲和能，并使用安德森电子亲和能模型计算了wz-和zb-合金之间的带偏移。对于zb-GaN/InN异质结，计算得到的导带（和价带）偏移为1.85（0.89）eV，比wz-对应物大0.25 eV（小0.26 eV）。这种具有大导带偏移的无极化zb-GaN/InGaN/GaN量子阱结构有潜力抑制电子泄漏电流和量子限制斯塔克效应（QCSE）。相反，计算得到zb-AlN/GaN异质结的导带（和价带）偏移为1.32（0.43）eV，比wz-情况小1.15 eV（大0.13 eV）。zb-AlN/GaN带偏移的显著减小归因于zb-AlN较小的间接带隙——zb-Al Ga N中直接带隙到间接带隙的转变点约为65%。zb-AlN势垒的小带隙和小导带偏移意味着电子可以分别以小偏压注入zb-AlN/GaN/AlN量子阱异质结构，并且在被量子阱捕获时能量损失较小，即热损失减少。三元III族氮化物的带隙并不线性依赖于合金成分，这意味着带偏移对成分的依赖是非线性的。结果，确定了导带偏移的大弯曲并归因于导带最小值的阳离子样行为，而价带偏移对成分的线性依赖归因于价带最大值的阴离子样特征。
