Embodiments generally relate to optoelectronic semiconductor devices such as photovoltaic cells. In one aspect, a method for forming a device includes forming an absorber layer made of gallium arsenide (GaAs) and having one type of doping, and forming an emitter layer made of a different material and having a higher bandgap than the absorber layer. An intermediate layer can be formed between emitter and absorber layers. A heterojunction and p-n junction are formed between the emitter layer and the absorber layer, where the p-n junction is formed at least partially within the different material at a location offset from the heterojunction. A majority of the absorber layer can be outside of a depletion region formed by the p-n junction. The p-n junction causes a voltage to be generated in the cell in response to the cell being exposed to light at a front side.