Adhikary S, Halder N, Chakrabarti S
Centre for Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology, Bombay, Mumbai 400076, India.
J Nanosci Nanotechnol. 2011 May;11(5):4067-72. doi: 10.1166/jnn.2011.3529.
The effect of rapid thermal annealing (RTA) on the optical properties of a 10 layer stacked InAs/GaAs quantum dot (QD) heterostructure where the QDs are overgrown with a combination of quaternary InAlGaAs and GaAs capping have been investigated. TEM micrographs showed that the shape of the QDs is preserved for annealing temperatures up to 800 degrees C. The peak emission wavelength of the investigated heterostructures remains stable on annealing at temperatures upto 750 degrees C, which is unusual in QD samples. This phenomenon is attributed due to the suppression of the strain-enhanced intermixing in such structures. One of the reasons behind such suppression is the strain driven phase separation of Indium from the overgrown quaternary alloy, which maintains an In rich region across the QD periphery thereby checking the out-diffusion of Indium from the dots. The overlapping vertical strain from the under lying dot layers in the QD stack also maintains a strain relaxed state at the QD base, thereby preventing the material mixing at the base of the pyramidal QDs. This stability of wavelength is of paramount importance in optoelectronic devices where the design is based on the emission wavelength of the active region.
研究了快速热退火（RTA）对10层堆叠的InAs/GaAs量子点（QD）异质结构光学性质的影响，其中量子点被四元InAlGaAs和GaAs盖帽的组合覆盖生长。透射电子显微镜图像显示，在高达800摄氏度的退火温度下，量子点的形状得以保留。所研究的异质结构的峰值发射波长在高达750摄氏度的温度下退火时保持稳定，这在量子点样品中是不寻常的。这种现象归因于此类结构中应变增强的混合受到抑制。这种抑制背后的一个原因是铟从覆盖生长的四元合金中应变驱动的相分离，这在量子点周边维持了一个富铟区域，从而抑制了铟从量子点中的向外扩散。量子点堆叠中下层量子点层的重叠垂直应变也在量子点底部维持了应变弛豫状态，从而防止了金字塔形量子点底部的材料混合。波长的这种稳定性在基于有源区发射波长进行设计的光电器件中至关重要。
