Aluminum Oxide Passivating Tunneling Interlayers for Molybdenum Oxide Hole-Selective Contacts

Aluminum oxide thin films fabricated via atomic layer deposition are introduced as passivating tunneling interlayers between hole-selective molybdenum oxide contacts and silicon absorbers. Surface recombination velocity and specific contact resistivity are reported as a function of Al
₂
O
₃
thickness. The effects of substrate chemical pretreatment, the thermal history of the Al
₂
O
₃
layers prior to MoO
_x
deposition, and the thermal history of the completed Al
₂
O
₃
/MoO
_x
stacks were also investigated. When an SiO
_x
/Al
₂
O
₃
passivating stack was incorporated and the completed test structure was annealed at 200 °C, the observed recombination velocities were reduced from ~10 000 cm/s for an unpassivated (initially hydrogen-terminated) Si/MoO
_x
direct contact to ~500 cm/s, while maintaining a contact resistivity at or below 0.1 Ω·cm
²
. The data demonstrate the capability of ultrathin Al
₂
O
₃
to improve Si/MoOx contact properties and may be of interest in the design of future Si heterojunctions.