InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells
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Published version
Author(s)
Type
Journal Article
Abstract
Quantum wires (QWRs) form naturally when growing strain balanced InGaAs/GaAsP multi-quantum wells (MQW) on GaAs [100] 6° misoriented substrates under the usual growth conditions. The presence of wires instead of wells could have several unexpected consequences for the performance of the MQW solar cells, both positive and negative, that need to be assessed to achieve high conversion efficiencies. In this letter, we study QWR properties from the point of view of their performance as solar cells by means of transmission electron microscopy, time resolved photoluminescence and external quantum efficiency (EQE) using polarised light. We find that these QWRs have longer lifetimes than nominally identical QWs grown on exact [100] GaAs substrates, of up to 1 μs, at any level of illumination. We attribute this effect to an asymmetric carrier escape from the nanostructures leading to a strong 1D-photo-charging, keeping electrons confined along the wire and holes in the barriers. In principle, these extended lifetimes could be exploited to enhance carrier collection and reduce dark current losses. Light absorption by these QWRs is 1.6 times weaker than QWs, as revealed by EQE measurements, which emphasises the need for more layers of nanostructures or the use light trapping techniques. Contrary to what we expected, QWR show very low absorption anisotropy, only 3.5%, which was the main drawback a priori of this nanostructure. We attribute this to a reduced lateral confinement inside the wires. These results encourage further study and optimization of QWRs for high efficiency solar cells.
Date Issued
2014-08-29
Date Acceptance
2014-08-20
Citation
Applied Physics Letters, 2014, 105 (8)
ISSN
1077-3118
Publisher
AIP Publishing
Journal / Book Title
Applied Physics Letters
Volume
105
Issue
8
Copyright Statement
© 2014 AIP Publishing LLC. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Applied Physics Letters and may be found at http://dx.doi.org/10.1063/1.4894424.
Sponsor
Commission of the European Communities
Grant Number
283798
Subjects
Science & Technology
Physical Sciences
Physics, Applied
Physics
CARRIER ESCAPE
QUANTUM WIRES
WELL NUMBER
PHOTOLUMINESCENCE
PERFORMANCE
DEPENDENCE
Applied Physics
09 Engineering
02 Physical Sciences
Publication Status
Published
Article Number
083124