Department of Electrical Engineering, Yale University, P.O. Box 208284, New Haven, Connecticut 06520, USA.
ACS Nano. 2013 Jun 25;7(6):5017-23. doi: 10.1021/nn400395y. Epub 2013 May 29.
Self-assembled quantum dots (SAQDs) grown under biaxial tension could enable novel devices by taking advantage of the strong band gap reduction induced by tensile strain. Tensile SAQDs with low optical transition energies could find application in the technologically important area of mid-infrared optoelectronics. In the case of Ge, biaxial tension can even cause a highly desirable crossover from an indirect- to a direct-gap band structure. However, the inability to grow tensile SAQDs without dislocations has impeded progress in these directions. In this article, we demonstrate a method to grow dislocation-free, tensile SAQDs by employing the unique strain relief mechanisms of (110)-oriented surfaces. As a model system, we show that tensile GaAs SAQDs form spontaneously, controllably, and without dislocations on InAlAs(110) surfaces. The tensile strain reduces the band gap in GaAs SAQDs by ~40%, leading to robust type-I quantum confinement and photoluminescence at energies lower than that of bulk GaAs. This method can be extended to other zinc blende and diamond cubic materials to form novel optoelectronic devices based on tensile SAQDs.
自组装量子点 (SAQD) 在双轴张应力下生长，可通过利用拉伸应变引起的强带隙减小来实现新型器件。低光学跃迁能的拉伸 SAQD 可在中红外光电子学这一具有重要技术意义的领域找到应用。在锗的情况下，双轴张应力甚至可以引起从间接带隙到直接带隙结构的非常理想的转变。然而，由于无法在无位错的情况下生长拉伸 SAQD，这些方向的进展受到了阻碍。在本文中，我们展示了一种通过利用（110）取向表面的独特应变释放机制来生长无位错拉伸 SAQD 的方法。作为模型体系，我们表明，拉伸 GaAs SAQD 在 InAlAs(110) 表面上自发、可控地形成，且无位错。拉伸应变将 GaAs SAQD 的带隙减小约 40%，导致在能量低于体 GaAs 的情况下出现稳健的 I 型量子限制和光致发光。这种方法可以扩展到其他闪锌矿和金刚石立方材料，以形成基于拉伸 SAQD 的新型光电设备。
