Mesa Separation of GaInP Solar Cells by Picosecond Laser Ablation

Laser ablation processes provide a potentially low cost and fast technology for microstructuring semiconductors, metals, or dielectrics. This paper deals with picosecond laser ablation (l = 532 nm, t ≈ 9 ps) of III-V semiconductors. In particular, the external threshold fluence of thermal ablation is determined for InP, GaAs, and GaP. Furthermore, the applicability of laser ablation to the electrical separation of III-V solar cells is discussed. In this context, current-voltage characteristics are presented comparing GaInP single-junction solar cells separated by picosecond laser ablation and wet-chemical mesa etching. The laser process leads to a significant drop in open-circuit voltage and fill factor which is explained by a more than three times larger (unpassivated) surface area.