MOVPE of n-doped GaAs and modulation doped GaAs/AlGaAs nanowires

Two different fabrication approaches were compared to obtain conductive GaAs nanowires: on one hand by modulation doping of GaAs/AlGaAs core/shell nanowires, on the other hand by Si-doping of GaAs nanowires. Modulation doped GaAs/AlGaAs core-shell nanowires were grown by selective area metal organic vapor phase epitaxy (MOVPE) on GaAs (1 1 1) substrates. The influences of growth parameters and mask design on aspect ratio of the core structures were investigated. The specialty of this study was that the growth mode was switched from vertical GaAs wire growth to the AlGaAs conformal shell overgrowth by intentionally changing the growth chemistry from the use of a more stable group III source - trimethylgallium (TMGa) to more easily decomposed sources - the alternative sources triethylgallium (TEGa) and dimethylethylaminealane (DMEAAI). It was found that the diameter and length of the core structures strongly depend on the arsenic partial pressure and growth temperature as well as mask design. The uniformity of shell growth is also influenced by the mask design. Additionally an alternative approach for the production of conductive GaAs nanowires was under study. To this end, the influence of Si-doping on GaAs core growth was investigated. it was found that doping has a detrimental impact on growth morphology leading to an undesirable enhanced growth rate on the nanowire side facets. (C) 2009 Elsevier B.V. All rights reserved.