Embodiments of the invention generally relate to photovoltaic devices. In one embodiment, a method for forming a gallium arsenide based photovoltaic device includes providing a semiconductor structure, the structure including an absorber layer comprising gallium arsenide and an emitter layer. A bypass function is provided in a p-n junction of the semiconductor structure, where under reverse-bias conditions the p-n junction breaks down in a controlled manner by a Zener breakdown effect. The absorber or base layer has a grading in doping concentration from a first doping level closest to the emitter layer to a second doping level away from the emitter layer, the second doping level being greater than the first doping level.