Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland.
Wroclaw Research Center EIT+ Sp. z o.o., ul. Stabłowicka 147, 54-066 Wrocław, Poland.
Sci Rep. 2017 Feb 2;7:41877. doi: 10.1038/srep41877.
The Fermi level position in (Ga,Mn)N has been determined from the period-analysis of GaN-related Franz-Keldysh oscillation obtained by contactless electroreflectance in a series of carefully prepared by molecular beam epitaxy GaN/GaMnN/GaN(template) bilayers of various Mn concentration x. It is shown that the Fermi level in (Ga,Mn)N is strongly pinned in the middle of the band gap and the thickness of the depletion layer is negligibly small. For x > 0.1% the Fermi level is located about 1.25-1.55 eV above the valence band, that is very close to, but visibly below the Mn-related Mn/Mn impurity band. The accumulated data allows us to estimate the Mn-related band offsets at the (Ga,Mn)N/GaN interface. It is found that most of the band gap change in (Ga,Mn)N takes place in the valence band on the absolute scale and amounts to -0.028 ± 0.008 eV/% Mn. The strong Fermi level pinning in the middle of the band gap, no carrier conductivity within the Mn-related impurity band, and a good homogeneity enable a novel functionality of (Ga,Mn)N as a semi-insulating buffer layers for applications in GaN-based heterostuctures.
（Ga,Mn）N 的费米能级位置已通过接触式电反射法在一系列由分子束外延生长的 GaN/GaMnN/GaN（模板）双层结构中确定，其中 Mn 浓度 x 各不相同，通过 GaN 相关的 Franz-Keldysh 振荡的周期性分析得到。结果表明，（Ga,Mn）N 中的费米能级强烈固定在带隙中间，耗尽层的厚度可以忽略不计。对于 x＞0.1%，费米能级位于价带上方约 1.25-1.55 eV，非常接近但明显低于 Mn 相关的 Mn/Mn 杂质带。积累的数据允许我们估计（Ga,Mn）N/GaN 界面处的 Mn 相关能带偏移。结果发现，（Ga,Mn）N 中大部分带隙变化发生在绝对尺度上的价带中，约为-0.028±0.008 eV/%Mn。在带隙中间的费米能级强钉扎、Mn 相关杂质带内没有载流子电导率以及良好的均匀性使（Ga,Mn）N 成为 GaN 基异质结构中半绝缘缓冲层的一种新功能。
