High Brightness InP Micropillars Grown on Silicon with Fermi Level Splitting Larger than 1 eV

The growth of III–V nanowires on silicon is a promising approach for low-cost, large-scale III–V photovoltaics. However, performances of III–V nanowire solar cells have not yet been as good as their bulk counterparts, as nanostructured light absorbers are fundamentally challenged by enhanced minorit...

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Bibliographic Details
Published in:Nano letters 2014-06, Vol.14 (6), p.3235-3240
Main Authors: Tran, Thai-Truong D, Sun, Hao, Ng, Kar Wei, Ren, Fan, Li, Kun, Lu, Fanglu, Yablonovitch, Eli, Chang-Hasnain, Constance J
Format: Article
Language:English
Subjects:
Applied sciences
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Cross-disciplinary physics: materials science
rheology
Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures
Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals
Electronics
Exact sciences and technology
Indium phosphides
Materials science
Molecular electronics, nanoelectronics
Nanocrystalline materials
Nanoscale materials and structures: fabrication and characterization
Nanostructure
Nanowires
Photovoltaic cells
Physics
Pillars
Quantum wires
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Silicon
Solar cells
Splitting
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Summary:The growth of III–V nanowires on silicon is a promising approach for low-cost, large-scale III–V photovoltaics. However, performances of III–V nanowire solar cells have not yet been as good as their bulk counterparts, as nanostructured light absorbers are fundamentally challenged by enhanced minority carriers surface recombination rates. The resulting nonradiative losses lead to significant reductions in the external spontaneous emission quantum yield, which, in turn, manifest as penalties in the open-circuit voltage. In this work, calibrated photoluminescence measurements are utilized to construct equivalent voltage–current characteristics relating illumination intensities to Fermi level splitting ΔF inside InP microillars. Under 1 sun, we show that splitting can exceed ΔF ∼ 0.90 eV in undoped pillars. This value can be increased to values of ΔF ∼ 0.95 eV by cleaning pillar surfaces in acidic etchants. Pillars with nanotextured surfaces can yield splitting of ΔF ∼ 0.90 eV, even though they exhibit high densities of stacking faults. Finally, by introducing n-dopants, ΔF of 1.07 eV can be achieved due to a wider bandgap energy in n-doped wurzite InP, the higher brightness of doped materials, and the extraordinarily low surface recombination velocity of InP. This is the highest reported value for InP materials grown on a silicon substrate. These results provide further evidence that InP micropillars on silicon could be a promising material for low-cost, large-scale solar cells with high efficiency.
ISSN:1530-6984
1530-6992
DOI:10.1021/nl500621j