Fu Y, Wang S M, Ferdos F, Sadeghi M, Larsson A
Physical Electronics and Photonics, Microtechnology Center at Chalmers, Department of Physics, Fysikgränd 3, Chalmers University of Technology and Gothenburg University, Göteborg, Sweden.
J Nanosci Nanotechnol. 2002 Jun-Aug;2(3-4):421-6. doi: 10.1166/jnn.2002.103.
We have fabricated and characterized three types of InAs quantum dots (QDs) with different InxGa1-xAs capping layers. Post-growth atomic force microscopy measurements show that the In0.2Ga0.8As/InAs structure has a smooth surface (dot-in-well structure), whereas the In0.4Ga0.6As/InAs structure revealed large QDs with a density similar to that underneath InAs QDs on GaAs (dot-in-dot). With increasing In mole fraction of the capping layer and increasing In0.4Ga0.6As thickness, the energy position of the room-temperature photoluminescence (PL) peak is red-shifted. The quantum dot-in-dot structure emits stronger room-temperature PL than does the quantum dot-in-well structure. With a spatially distributed strain in the InAs quantum dot, we have solved the three-dimensional Schrödinger equation by the Green's function theory for the eigenvalues and eigen wave functions. It is concluded that the ground state increases its wave function penetration into the low-barrier InxGa1-xAs capping layer so that its energy position is red-shifted. The reduced PL peak intensity of the dot-in-well (compared with GaAs covered dots) is due to the reduced overlapping between the ground state and the extended states above the GaAs barrier. The overlapping reduction in the dot-in-dot is over compensated for by the reduced relaxation energy (full width at half-maximum), indicating the importance of the sample quality in determining the PL intensity.
我们制备并表征了三种具有不同InxGa1-xAs盖帽层的InAs量子点（QD）。生长后原子力显微镜测量表明，In0.2Ga0.8As/InAs结构具有光滑表面（点在阱结构），而In0.4Ga0.6As/InAs结构显示出大的量子点，其密度与GaAs上InAs量子点下方的密度相似（点在点）。随着盖帽层In摩尔分数的增加和In0.4Ga0.6As厚度的增加，室温光致发光（PL）峰的能量位置发生红移。点在点结构在室温下发出的PL比点在阱结构更强。利用InAs量子点中的空间分布应变，我们通过格林函数理论求解了三维薛定谔方程以获得本征值和本征波函数。得出的结论是，基态增加了其波函数向低势垒InxGa1-xAs盖帽层的穿透，从而使其能量位置发生红移。点在阱（与GaAs覆盖的点相比）的PL峰强度降低是由于基态与GaAs势垒上方扩展态之间的重叠减少。点在点中的重叠减少被降低的弛豫能量（半高宽）过度补偿，这表明样品质量在确定PL强度方面的重要性。
