Type II heterojunction tunnel diodes based on GaAs for multi-junction solar cells: Fabrication, characterization and simulation
Résumé
In this work, Molecular Beam Epitaxy (MBE) grown tunnel junctions (TJs) based on GaAs(Sb)(In) materials are experimentally and numerically studied. From simple GaAs TJs grown with various n-doping levels, we develop a semi-classical interband tunneling model able to quantify the magnitude of the tunneling current density, which shows that direct interband tunneling is the predominant tunneling mechanism in GaAs tunnel junctions instead of trap-assisted-tunneling mechanisms. Numerical simulations based on non equilibrium perturbation theory through Non Equilibrium Green's Functions (NEGF) and a multi-band kp hamiltonian that includes both gamma and L valleys were performed by the IM2NP (Marseille) and confirmed this result. In order to further improve the performance of the TJs, we are fabricating a type II tunnel heterojunction based on GaAsSb and InGaAs materials.
Mots clés
direct interband tunneling
tunneling current density
semiclassical interband tunneling
numerical simulations
GaAs tunnel junctions
MBE
n-doping levels
molecular beam epitaxy
multijunction solar cells
type II heterojunction tunnel diodes
tunnel diodes
solar cells
InGaAs
nonequilibrium perturbation
nonequilibrium Green's functions
gallium arsenide
k.p calculations
GaAsSb
InGaAs materials
GaAsSb materials
multiband kp Hamiltonian
indium compounds
current density
numerical analysis
semiconductor doping
molecular beam epitaxial growth
Green's function methods
III-V semiconductors
semiconductor heterojunctions
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