Barik S, Tan H H, Wong-Leung J, Jagadish C
Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, The Australian National University, Canberra, Australian Capital Territory 0200, Australia.
J Nanosci Nanotechnol. 2010 Mar;10(3):1525-36. doi: 10.1166/jnn.2010.2024.
InAs quantum dots (QDs) are grown on InP or lattice matched GaInAsP buffers using horizontal flow metal-organic chemical vapor deposition (MOCVD) at a pressure of 180 mbar. A range of techniques, such as photoluminescence (PL), atomic force microscopy, and plan-view transmission electron microscopy is used to characterize the QD and other semiconductor layers. The effects of different growth parameters, such as V/III ratio and growth time, and the effects of buffer layers, interlayers, and cap layers are investigated and the optimized growth conditions are discussed. In the case of the QDs grown on InP buffers, the As/P exchange reaction is found to be prominent. A very thin (0.6 nm) GaAs interlayer grown between the buffer and the QD layers consumes segregated indium and minimizes the As/P exchange reaction. As a result, the QD PL emission energy increases, the PL intensity improves, and the PL linewidth decreases. The experimental results show that by changing the thickness of a GaAs interlayer (0.3-0.6 nm), the emission wavelength/energy of the QDs grown on a lattice matched GaInAsP buffer can be tuned over a wide range covering 1550 nm. However, further increase in the thickness of the GaAs interlayer results in the agglomeration of the QDs and the deterioration of the QD optical properties. Detailed microscopy studies show that capped QDs have higher density and are smaller in size on average compared to uncapped QDs, which undergo coalescence during cooling of the sample after growth. Overall, the QDs grown for shorter time with a smaller V/III ratio (approximately 8) show improved PL intensity and narrower PL linewidth.
采用水平流动金属有机化学气相沉积（MOCVD）在180毫巴的压力下，在InP或晶格匹配的GaInAsP缓冲层上生长InAs量子点（QD）。使用一系列技术，如光致发光（PL）、原子力显微镜和平面透射电子显微镜来表征量子点和其他半导体层。研究了不同生长参数（如V/III比和生长时间）的影响以及缓冲层、中间层和帽层的影响，并讨论了优化的生长条件。在InP缓冲层上生长的量子点的情况下，发现As/P交换反应很显著。在缓冲层和量子点层之间生长的非常薄（0.6纳米）的GaAs中间层消耗了偏析的铟，并使As/P交换反应最小化。结果，量子点的PL发射能量增加，PL强度提高，PL线宽减小。实验结果表明，通过改变GaAs中间层的厚度（0.3 - 0.6纳米），在晶格匹配的GaInAsP缓冲层上生长的量子点的发射波长/能量可以在覆盖1550纳米的宽范围内进行调谐。然而，GaAs中间层厚度的进一步增加会导致量子点的团聚和量子点光学性质的恶化。详细的显微镜研究表明，与未盖帽的量子点相比，盖帽的量子点具有更高的密度且平均尺寸更小，未盖帽的量子点在生长后样品冷却过程中会发生合并。总体而言，以较小的V/III比（约8）生长较短时间的量子点显示出改善的PL强度和更窄的PL线宽。
