Anisotropic absorption and emission of bulk (1(1)over-bar00) AlN
Anisotropic absorption and emission of bulk (1(1)over-bar00) AlN
复制标题
DOI：
10.1103/physrevb.87.235209
复制
发表时间：
2013-06-24
影响因子：
3.7
通讯作者：
Goldhahn, Ruediger
中科院分区：
文献类型：
--
作者：
Feneberg, Martin;Romero, Maria Fatima;Goldhahn, Ruediger
从吸收和发射两方面研究了纤锌矿AlN的本征各向异性光学性质。通过研究允许电场E垂直(E垂直于c)和平行(E平行于c)的高质量块体晶体的(1(1)Over bar 00)平面，获得了对六方材料光学响应各向异性的全面了解。光谱椭偏测量得到了从0.58到20 eV的普通(epsilon(垂直))和异常(epsilon(平行))介电函数(DFS)。实验数据与最近计算的DFS的比较表明，库仑相互作用不仅对基吸收边附近的光谱依赖性有很大的影响，而且对通常用van Hove奇点来讨论的高能特征也有很大的影响。Epsilon(平行于)和epsilon(垂直于)的二阶导数的拟合为这个范围内的主要特征提供了跃迁能量。以自由激子、激子-声子复合体和激子连续谱为主的基态吸收边附近的DFS被反射率和基于同步辐射的光致发光激发研究独立地证实。得到了带隙、晶场(Delta(Cf)=-221+/-2 meV)和自旋轨道分裂(Delta(So)=13+/-2 meV)的值。此外，在计算激子结合能时，我们还得到了ε(S垂直)=7.65和epsilon(S平行)=9.21的静态介电常数的精确值。用光致发光研究了同一样品的发射性质。
The intrinsic anisotropic optical properties of wurtzite AlN are investigated in absorption and emission. Full access to the anisotropy of the optical response of the hexagonal material is obtained by investigating the (1 (1) over bar 00) plane of a high-quality bulk crystal allowing electric field E polarization perpendicular (E perpendicular to c) and parallel (E parallel to c) to the optical axis c. Spectroscopic ellipsometry yields the ordinary (epsilon(perpendicular to)) and extraordinary (epsilon(parallel to)) dielectric functions (DFs) from 0.58 up to 20 eV. The comparison of the experimental data with recently calculated DFs demonstrates that Coulomb interaction has a strong impact not only on the spectral dependence around the fundamental absorption edge but also on the high-energy features usually discussed in terms of van Hove singularities. The fits of the second-order derivatives of epsilon(parallel to) and epsilon(perpendicular to) provide the transition energies for the main features in this range. The DFs close to the fundamental absorption edge, dominated by free excitons, exciton-phonon complexes, and the exciton continuum, are independently confirmed by reflectivity and synchrotron-based photoluminescence excitation studies. Values for the band gaps, the crystal field (Delta(cf) = -221 +/- 2 meV), and spin-orbit splittings (Delta(so) = 13 +/- 2 meV) are obtained. Furthermore, we obtain accurate values for the static dielectric constants of epsilon(S perpendicular to) = 7.65 and epsilon(S parallel to) = 9.21, entering, e. g., the calculations of exciton binding energies. Photoluminescence is used to investigate the emission properties of the same sample.