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13 February 2009 Selective MOCVD growth of InGaAs/GaAs and InGaAs/InP quantum dots employing diblock copolymer nanopatterning
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The conventional approach to fabricate semiconductor based QDs is based on the Stranski-Krastnow (SK) growth mode, which has enjoyed considerable success in device applications. However, the SK QD approach is complicated by the randomness of the QD size distribution and inherent presence of the wetting layer. Carrier leakage to the wetting layer has been identified as one of the underlying causes for low optical gain and high temperature sensitivity in diode lasers. To fully exploit the potential advantages of ideal Quantum Dots (i.e. full 3D carrier confinement), elimination of the wetting layer and a uniform mono-modal QD size distribution is needed. Nanopatterning with selective MOCVD QD growth has potential for achieving a higher degree of control over the QD formation, compared with the SK process. Furthermore, the problematic wetting layer states are eliminated and improved optical gain is expected. The QD patterning is prepared by dense nanoscale (20-30 nm diameter) diblock copolymer lithography, which consists of perpendicularly ordered cylindrical domains of polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) matrix. For selective MOCVD growth, a dielectric template mask was utilized and the polymer patterning is transferred on it. The resulting GaAs QD densities are larger than 5×1010/cm2, comparable to SK growth mode, with a nearly monomodal QD size distribution. Variable temperature PL has been used to characterize the optical properties of capped InGaAs QDs on GaAs (λ ~ 1.1 μm) and InP (λ ~ 1.5 μm) substrates.
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Luke J. Mawst, Joo Hyung Park, Manish K. Rathi, Thomas F. Kuech, Varun B. Verma, and James J. Coleman "Selective MOCVD growth of InGaAs/GaAs and InGaAs/InP quantum dots employing diblock copolymer nanopatterning", Proc. SPIE 7224, Quantum Dots, Particles, and Nanoclusters VI, 722407 (13 February 2009);


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