Lozac'h Mickael, Ueda Shigenori, Liu Shitao, Yoshikawa Hideki, Liwen Sang, Wang Xinqiang, Shen Bo, Sakoda Kazuaki, Kobayashi Keisuke, Sumiya Masatomo
Photonic Materials Unit, National Institute for Materials Science, Tsukuba 305-0044, Japan; Doctoral Program in Materials Science and Engineering, Tsukuba University, Tsukuba 305-8573, Japan.
Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148, Japan.
Sci Technol Adv Mater. 2013 Feb 21;14(1):015007. doi: 10.1088/1468-6996/14/1/015007. eCollection 2013 Feb.
Core-level and valence band spectra of In Ga N films were measured using hard x-ray photoemission spectroscopy (HX-PES). Fine structure, caused by the coupling of the localized Ga 3d and In 4d with N 2s states, was experimentally observed in the films. Because of the large detection depth of HX-PES (∼20 nm), the spectra contain both surface and bulk information due to the surface band bending. The In Ga N films ( = 0-0.21) exhibited upward surface band bending, and the valence band maximum was shifted to lower binding energy when the mole fraction of InN was increased. On the other hand, downward surface band bending was confirmed for an InN film with low carrier density despite its n-type conduction. Although the Fermi level () near the surface of the InN film was detected inside the conduction band as reported previously, it can be concluded that in the bulk of the film must be located in the band gap below the conduction band minimum.
使用硬X射线光电子能谱（HX-PES）测量了InGaN薄膜的芯能级和价带光谱。在薄膜中通过实验观察到了由局域化的Ga 3d和In 4d与N 2s态耦合引起的精细结构。由于HX-PES的探测深度较大（约20纳米），由于表面能带弯曲，光谱包含了表面和体相信息。InGaN薄膜（x = 0 - 0.21）表现出向上的表面能带弯曲，并且当InN的摩尔分数增加时，价带最大值向较低结合能移动。另一方面，尽管具有n型导电性，但对于低载流子密度的InN薄膜，确认了向下的表面能带弯曲。尽管如先前报道的那样，在InN薄膜表面附近的费米能级（EF）在导带内被检测到，但可以得出结论，薄膜体相中的EF必定位于导带最小值以下的带隙中。
