Huang Wenqi, Yang Hong, Cheng Buwen, Xue Chunlai
School of Applied Science, Beijing Information Science & Technology University, Beijing, 100101, China.
Phys Chem Chem Phys. 2017 Oct 11;19(39):27031-27037. doi: 10.1039/c7cp05840c.
N-Doping is an effective approach for improving the lighting efficiency of GeSn alloys. As each doping element has an atomic radius and electronegativity value different from those of the host atoms, the shape of the GeSn band is affected. However, no recent studies considering this phenomenon have been reported. For this reason, first-principles calculations combined with the GGA+U method and supercell models have been employed to precisely investigate the structural properties, band structures, and optical gains of GeSn when doped with different V-group elements (including P, As, Sb, and Bi). With regard to the structural properties, the results indicate that they all exhibit a positive deviation from Vegard's law; GeSnP has the largest bowing coefficient. The bandgap results indicate that doping with P and As does not assist in converting GeSn into a direct bandgap material, while doping with Sb and Bi has positive effects on the transition of GeSn; the corresponding crossover values are 1.89 and 1.58%, respectively. The calculated optical gain indicates that the net gain of GeSn will reach a maximum when the injected carrier density is ∼1 × 10 cm, and it will increase as the doping concentration increases. The effects of the doping elements on the optical gain of GeSn can be ranked as Bi > Sb > As > P.
N型掺杂是提高GeSn合金发光效率的有效方法。由于每种掺杂元素的原子半径和电负性值与主体原子不同，GeSn能带的形状会受到影响。然而，最近尚未有考虑这种现象的研究报道。因此，采用结合广义梯度近似（GGA）+U方法和超胞模型的第一性原理计算，精确研究了GeSn在掺杂不同V族元素（包括P、As、Sb和Bi）时的结构性质、能带结构和光学增益。关于结构性质，结果表明它们都表现出与维加德定律的正偏差；GeSnP具有最大的弯曲系数。能带隙结果表明，掺杂P和As无助于将GeSn转变为直接带隙材料，而掺杂Sb和Bi对GeSn的跃迁有积极影响；相应的交叉值分别为1.89%和1.58%。计算得到的光学增益表明，当注入载流子密度约为1×10 cm时，GeSn的净增益将达到最大值，并且会随着掺杂浓度的增加而增加。掺杂元素对GeSn光学增益的影响排序为Bi > Sb > As > P。
