Engineering dislocations and nanovoids for high-efficiency III–V photovoltaic cells on silicon

The use promising group III-V materials for photovoltaic applications is hindered by the high density of threading dislocations when integrated with silicon technology. Here, we present an electrochemical deep etching strategy to drastically reduce the defect density. We seek to accommodate the effects of the lattice mismatch by introducing nanovoids inside the Ge/Si interface, which intercept dislocations, facilitating their subsequent annihilation and prevent them from reaching the active layers of the device. This allows an appreciable dislocation density, which unlocks the potential of providing high quality Ge-on-Si virtual substrates for growing lattice-matched III-V photovoltaics.