Photogating in graphene field-effect phototransistors: Theory and observations

In this work, we investigate graphene field-effect phototransistor based on photogating. We discuss the theory of this effect and predict such characteristics as the dependence of photoresponse on the gate voltage. To verify our considerations, we fabricate devices on different semiconductor substrates (silicon, germanium or gallium arsenide) and measure their properties. We demonstrate that photogating reveals opportunities for the development of highly sensitive broadband photodetectors from ultraviolet to mid-infrared ranges.