PHOTO : Devices - Tunnel junctions
Tunnel junctions are key elements in multijunction solar cells since they ensure the electrical connections between the different absorbing subcells which must be as perfectly conductive and transparent as possible. The impact of the tunnel junction is even more challenging for a high number of tandem cells, such as for the six-junction solar cell which holds the absolute conversion efficiency record.
Our research work on this topic aims to improve the understanding of the transport mechanisms in GaAs/GaAs homojunctions and GaInAs/GaAsSb heterojunctions, by focusing on the characterization and the fine modeling of III-V heterostructures. The goal is to propose new heterostructures optimized for high peak currents for high concentration photovoltaic applications. The improvement of the electrical properties of tunnel junctions is also a very important scientific target in the fields of microelectronics and optoelectronics for tunnel field effect transistors (TFET), VCSELs, cascading active regions for best performing lasers and high-conductivity thin films to improve the electrical injection in large surface devices.
Gain on peak current density shown for a GaAs tunnel junction with a type II heterostructure. Inset : NEGF simulations of the band edge profiles and local density of states for thick (a) and thin (b) tunnel junctions.
LNE Trappes, IM2NP Université Aix-Marseille, IES Université Montpellier, ONERA, CNES
EURAMET SolCell project, CIFRE LNE, PhD co-supervised by CNES/ONERA
Louarn, K. et al. "Thickness limitation of band-to-band tunneling process in GaAsSb/InGaAs type-II tunnel junctions designed for multijunction solar cells." ACS Applied Energy Materials 2, 1149-1154, 2019. Louarn, K. et al. "Multiband corrections for the semi-classical simulation of interband tunneling in GaAs tunnel junctions." Journal of Physics D: Applied Physics 50, 385109, 2017. Louarn, K. et al. "Effect of low and staggered gap quantum wells inserted in GaAs tunnel junctions." Journal of Physics D: Applied Physics 51, 145107, 2018. Louarn, K. et al. "Modelling of interband transitions in GaAs tunnel diode." Semiconductor Science and Technology 31, 06LT01, 2016.