A semiconductor-graphene heterojunction quad-detector pairs a semiconductor material with curved graphene strips in a quad-cell design. Graphene has been shown to have exceptional electrical properties that enhance the operation of semiconductor photodetectors. These properties address limitations of current semiconductor quad-cell devices by drastically increasing their sensitivity. According to an aspect of the present disclosure, a position detector includes a substrate having windows formed therein. Four graphene pads each having a plurality of curved strips are formed on the substrate. Each of the plurality of curved strips have a first end connected to a grounded conductor pad and a second end connected to one of four signal conductor pads.