TY - JOUR
T1 - Analysis of recombination processes in polytype gallium arsenide nanowires
AU - Vulic, Natasa
AU - Goodnick, Stephen M.
N1 - Funding Information:
Natasa Vulic's work has been funded through the Joint U.S. Fulbright Scholar/Swiss FCS Scholarship and the Arizona State University Dean's Fellowships . The authors would like to acknowledge Prof. Anna Fontcuberta i Morral's Laboratory of Semiconductor Materials (Ecole Polytechnique Fédérale de Lausanne) where samples were prepared and characterized. The authors would like to thank Dr. Gözde Tütüncüoglu and Dr. Heidi Potts for providing the samples, Dr. Dmitry Mikulik for assisting in sample preparation, and Luca Francaviglia for his assistance with the PL set-up and providing TEM images. The authors would especially like to thank Dr. Yannik Fontana for helpful discussion throughout the project. This material is based upon work supported in part by the National Science Foundation (NSF) and the Department of Energy ( DOE ) under NSF CA No. EEC-1041895 . Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of NSF or DOE.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2019/2
Y1 - 2019/2
N2 - Here we investigate recombination in polytype gallium arsenide (GaAs) nanowires (NWs) for photovoltaic applications, through photoluminescence studies coupled with rate equation analysis. Polytype NWs exhibit switching between zinc-blende (ZB) and wurtzite (WZ) crystal phases along the wire due to rotational twinning during self-catalyzed growth. When photons are absorbed in polytype NWs, electrons and holes separate: in the simplest case, electrons quickly thermalize to the band-edge of the ZB phase, while holes thermalize to the band-edge of the WZ phase, recombining indirectly in space across the type-II offset. The recombination mechanisms of this system are investigated experimentally through time-resolved photoluminescence (TRPL) at liquid helium temperature, and time-integrated photoluminescence (TIPL) at various temperatures, for the baseline case of AlGaAs capped GaAs NWs. The effects of the surface recombination on sub-bandgap transitions are also investigated using Al2O3 and no capping at the surface. We infer that carriers quickly thermalize to the spatially closest, lowest energy level, where they radiatively recombine across a sub-bandgap energy gap at a slower radiative rate than band-to-band. We use a rate equation model to investigate different configurations of polytype defects along the wire, including the effects of the surface and temperature, which compares well with experiment considering spatially indirect recombination between different polytypes, and defect-related recombination due to twin planes and other defects.
AB - Here we investigate recombination in polytype gallium arsenide (GaAs) nanowires (NWs) for photovoltaic applications, through photoluminescence studies coupled with rate equation analysis. Polytype NWs exhibit switching between zinc-blende (ZB) and wurtzite (WZ) crystal phases along the wire due to rotational twinning during self-catalyzed growth. When photons are absorbed in polytype NWs, electrons and holes separate: in the simplest case, electrons quickly thermalize to the band-edge of the ZB phase, while holes thermalize to the band-edge of the WZ phase, recombining indirectly in space across the type-II offset. The recombination mechanisms of this system are investigated experimentally through time-resolved photoluminescence (TRPL) at liquid helium temperature, and time-integrated photoluminescence (TIPL) at various temperatures, for the baseline case of AlGaAs capped GaAs NWs. The effects of the surface recombination on sub-bandgap transitions are also investigated using Al2O3 and no capping at the surface. We infer that carriers quickly thermalize to the spatially closest, lowest energy level, where they radiatively recombine across a sub-bandgap energy gap at a slower radiative rate than band-to-band. We use a rate equation model to investigate different configurations of polytype defects along the wire, including the effects of the surface and temperature, which compares well with experiment considering spatially indirect recombination between different polytypes, and defect-related recombination due to twin planes and other defects.
KW - Modeling
KW - Nanowires
KW - Next generation photovoltaics
KW - Polytypism
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U2 - 10.1016/j.nanoen.2018.11.030
DO - 10.1016/j.nanoen.2018.11.030
M3 - Article
AN - SCOPUS:85057083746
SN - 2211-2855
VL - 56
SP - 196
EP - 206
JO - Nano Energy
JF - Nano Energy
ER -