An evaporated aluminum metallization for high efficiency GaAs solar cells

A thick aluminum grid metallization for p-n GaAs solar cells which can be deposited completely by evaporation has been developed. The contacts are weldable, have low specific contact resistance (5×10 ^-6 Ω-cm²) to p-GaAs, and are compatible with the subsequent processing steps used on a GaAs solar cell pilot line. The total metallization is approximately 4 μm thick with nearly vertical sidewalls, and height-to-width aspect ratios greater than one can be achieved. This cross-sectional geometry provides sufficient current-carrying capacity with minimum obscuration. Large-area (4 cm²) devices have been fabricated with this aluminum metal scheme, resulting in a median efficiency of 20.52% (one sun, AM0). Fabrication details, test results for large-area cells, and applications for high-temperature stability, and concentrator cells are discussed