High Tunneling Current and Thermally Stable AlGaAs Tunnel Junctions Enabled by Hybrid Delta Doping for III-V/Si Epitaxial Tandem Cells

Abstract

Thermally stable III-V tunnel junctions (TJs) with a high tunneling current are essential for integrating III-V/Si tandem solar cells via epitaxial growth. Here, we present TJs based on 1.55-1.65 eV AlGaAs materials utilizing a Si:GaAs quantum well (QW) layer delta-doped with two different dopants, Si or Te. The hybrid delta doping structure, which is formed by the incorporation of Te as a delta doping species, boosts tunneling currents as well as improves thermal stability after annealing at 600 degrees C for 90 min by minimizing several Te-related issues such as delayed incorporation, the memory effect, and even the Si amphoteric effect. Moreover, 1.65 eV AlGaAs solar cells are successfully demonstrated when grown with a hybrid delta-doped AlGaAs TJ. This study shows that the hybrid delta doping technique is a simple but powerful method to improve both the TJ performance and thermal stability for advanced III-V/Si tandem solar cells.