Low cost process for ohmic contacts on [formula omitted] concentrator solar cells based on palladium and gold deposition

Abstract

A new fabrication process for high concentration GaAs/ Ga 1−x Al x As solar cells is described that does not require any vapour deposition of the ohmic contacts. The process is based on the electroless deposition of palladium as a p-type contact, while electrolytic gold is used as an n-type contact. Palladium exhibits good ohmic behaviour without any thermal alloying. From test patterns the specific resistance r c of the ohmic contacts turns out to be 10 −4 Ω cm 2 for palladium on p-type GaAs and 7 × 10 −6 Ω cm 2 for gold on n-type GaAs. Several solar cells were fabricated and tested at 800 suns. The devices have series resistances lower than 10 mΩ cm 2 and thus are comparable with solar cells based on evaporated ohmic contacts.