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14 March 2016 1.7eV Al0.2Ga0.8As solar cells epitaxially grown on silicon by SSMBE using a superlattice and dislocation filters
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Lattice-mismatched 1.7eV Al0.2Ga0.8As photovoltaic solar cells have been monolithically grown on Si substrates using Solid Source Molecular Beam Epitaxy (SSMBE). As a consequence of the 4%-lattice-mismatch, threading dislocations (TDs) nucleate at the interface between the Si substrate and III-V epilayers and propagate to the active regions of the cell. There they act as recombination centers and degrade the performances of the cell. In our case, direct AlAs/GaAs superlattice growth coupled with InAlAs/AlAs strained layer superlattice (SLS) dislocation filter layers (DFLSs) have been used to reduce the TD density from 1×109cm-2 to 1(±0.2)×107cm-2. Lattice-matched Al0.2Ga0.8As cells have also been grown on GaAs as a reference. The best cell grown on silicon exhibits a Voc of 964mV, compared with a Voc of 1128mV on GaAs. Fill factors of respectively 77.6% and 80.2% have been calculated. Due to the lack of an anti-reflection coating and the non-optimized architecture of the devices, relatively low Jsc have been measured: on Si and on GaAs. The difference in short-circuit currents is believed to be caused by a difference of thickness between the samples due to discrepancies in the calibration of the MBE prior to each growth. The bandgap-voltage offset of the cells, defined as Eg/q-Voc, is relatively high on both substrates with 736mV measured on Si versus 572mV on GaAs. The non-negligible TD density partly explains this result on Si. On GaAs, non-ideal growth conditions are possibly responsible for these suboptimal performances.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Arthur Onno, Jiang Wu, Qi Jiang, Siming Chen, Mingchu Tang, Yurii Maidaniuk, Mourad Benamara, Yuriy I. Mazur, Gregory J. Salamo, Nils-Peter Harder, Lars Oberbeck, and Huiyin Liu "1.7eV Al0.2Ga0.8As solar cells epitaxially grown on silicon by SSMBE using a superlattice and dislocation filters", Proc. SPIE 9743, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices V, 974310 (14 March 2016);

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