Deák Peter, Han Miaomiao, Lorke Michael, Tabriz Meisam Farzalipour, Frauenheim Thomas
Bremen Center for Computational Materials Sci., University of Bremen, PoB 330440, D-28334 Bremen, Germany.
J Phys Condens Matter. 2020 Jul 1;32(28):285503. doi: 10.1088/1361-648X/ab7fdb.
GaSe is a layered semiconductor with an optical band gap tunable by the number of layers in a thin film. This is promising for application in micro/optoelectronics and photovoltaics. However, for that, knowledge about the intrinsic defects are needed, since they may influence device behavior. Here we present a comprehensive study of intrinsic point defects in both bulk and monolayer (ML) GaSe, using an optimized hybrid functional which reproduces the band gap and is Koopmans' compliant. Formation energies and charge transition levels are calculated, the latter in good agreement with available experimental data. We find that the only intrinsic donor is the interlayer gallium interstitial, which is absent in the case of the ML. The vacancies are acceptors, the selenium interstitial is electrically inactive, and small intrinsic defect complexes have formation energies too high to play a role in the electronic properties of samples grown under quasi-equilibrium conditions. Bulk GaSe is well compensated by the intrinsic defects, and is an ideal substrate. The ML is intrinsically p-type, and p-type doping cannot be compensated either. The opening of the band gap changes the defect physics considerably with respect to the bulk.
GaSe是一种层状半导体，其光学带隙可通过薄膜中的层数进行调节。这在微纳电子学和光伏领域具有应用前景。然而，要实现这一点，需要了解其本征缺陷，因为它们可能会影响器件性能。在此，我们使用一种优化的杂化泛函对体相和单层（ML）GaSe中的本征点缺陷进行了全面研究，该泛函能重现带隙且符合库普曼斯定理。计算了形成能和电荷转移能级，后者与现有实验数据吻合良好。我们发现唯一的本征施主是层间镓间隙原子，在单层情况下不存在。空位是受主，硒间隙原子电中性，并且小的本征缺陷复合体的形成能过高，在准平衡条件下生长的样品的电子性质中不起作用。体相GaSe被本征缺陷很好地补偿，是理想的衬底。单层本质上是p型的，p型掺杂也无法被补偿。带隙的打开相对于体相而言，极大地改变了缺陷物理。
