Abstract: A semiconductor-based optoelectronic device such as a solar cell has an n-type layer and a p-type layer, together forming a p-n junction. Contact regions are formed on the device, with light-receiving regions between contact regions. A window layer is formed over the n-type layer or the p-type layer at the light-receiving region, the window layer promoting reduced carrier recombination at the surface of the n-type or p-type layer, and/or reflection of minority carriers in the n-type or p-type layer towards the p-n junction. The device has a window protection layer formed over the window layer, the window protection layer providing protection from degradation of the window layer during manufacture and/or operation of the device. For GaAs-based devices the window layer may be Al0.9Ga0.1As and the window protection layer may be GaAs. Additionally, an AlAs etch stop layer may be provided over the window protection layer.