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 ( $\lambda = 532\,{\text{nm}}$ , $\tau \approx 9\,{\rm{ps}}$ ) 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.