Fabrication of CdTe Quantum Dot Arrays on GaAs utilizng Nanoporous Alumina Masks
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M11.38.1
Fabrication of CdTe Quantum Dot Arrays on GaAs utilizng Nanoporous Alumina Masks Mi Jung, Hong Seok Lee1, Hong Lee Park1, Sun-il Mho* Department of Molecular Science and Technology, Ajou University, Suwon 443-749, Korea 1 Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea
ABSTRACT The uniformity and reproducibility of the CdTe QD arrays on the GaAs substrates can be improved by using a nanoporous mask. The CdTe QDs on the GaAs substrate were grown by a molecular beam epitaxy (MBE) method. The nanoporous alumina masks used for the fabrication of QD arrays have the thickness from 0.3 µm to 5 µm with the nanochannels of ~ 80 nm 10 -2 diameter and the pore density of ~ 10 cm . When the thickness of the alumina mask used for the CdTe QD growth was about 300 nm, the CdTe QD arrays formed as a replica of the nanochannels of the mask. Smaller self-assembled CdTe QDs located randomly were produced by using the thicker nanochannel mask than 0.5 µm. The thickness of the nanochannel mask controls the size of the CdTe/GaAs QDs.
INTRODUCTION The fabrication of quantum dot (QD) structures is attractive because of the applications in electronic and optoelectronic devices, such as single electron transistors, laser diodes, and infrared photodetectors [1, 2]. Photoluminescence characteristics of the compound semiconductor QDs strongly depend on the size of the QDs. The CdTe QD structures are of interest because of their potential applications in the optoelectronic devices in the visible range [3]. However, little work has been performed on the heterostructure CdTe/GaAs QDs because of the inherent growth problem caused by the different lattice constants (CdTe: 6.48 Å, GaAs: 5.65 Å). The strain-induced self-assembled CdTe islands are known to form due to the StranskiKranstanov growth mode [4]. It is a challenge of technological importance to prepare wellordered QDs with homogeneous sizes. The uniformity and reproducibility of QD structure can be improved by using a nanochannel mask [5-7]. Channel-array materials of nanometer-scale are of interest in recent years. An alumina mask with well-orderd nanopores has been used to fabricate nanostructures using electrodeposition, chemical vapor deposition, and molecular beam epitaxy (MBE). The geometry of the anodized alumina mask may be schematically represented as a close-packed array of columnar hexagonal cells, each containing a central pore normal to the substrate. The well-ordered nanochannel alumina masks were able to obtain by a two-step anodizing process [8, 9]. The cell size of the porous alumina is controlled by the anodization voltage. In this work, the growth of uniform CdTe QD arrays on the GaAs substrate by MBE method is pursued using well ordered nanochannel alumina masks. The growth rate and characteristics of CdTe QDs on the GaAs substrate with the mask depend on the temperatures of the GaAs substrate and of the Cd and Te sources, and the thickness of the nanochannel masks. The thickness of the alumina mask used for the CdTe QD growth
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