Control of Self-Assembled Semiconductor Quantum Department of Electronic Engineering |
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| Self-assembled semiconductor quantum dots (QDs) are much attractive for various device applications: QD laser, single photon source and detector, quantum computing, single electron transistor and memory, spin-controlled devices and so on. In order to realize such QD devices, the QD structure must be controlled precisely. In particular, a large inhomogeneous broadening in the QD structure is one of important problems. In addition, high QD density is also requested for realization of QD lasers with high performance. Recently we have demonstrated high-uniformity and high-density InAs QDs on GaAs(001) substrates by Sb-mediated Stranski-Krastanov (SK) growth method. The underlying Sb-terminated GaAs layers enhanced the nucleation of the three-dimensional (3D) InAs islands, and high QD density of 1×1011 cm-2 was achieved successfully, as shown in Fig.1. |
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| A precise control of the quantum dot (QD) position and a selective arrangement of QDs are also needed for some device applications. Lithography and etching techniques are often used for a selective fabrication of QDs on non-planar substrates. We have been investigating the self-alignment of InAs-QD array on a strained buffer layer without lithography and etching processes. Recently, 1D array structures of InAs QDs (QD chains) were successfully formed on self-formed GaAs mesa-stripes, grown on the strained InGaAs/GaAs buffer layer, as shown in Fig.2. Additionally, we have been attempting the self-formation of 2D-QD array structures. |
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