Ultra-low-power photodetector based on a high-photoresponse, plasmonic-effect-induced gateless quasi-freestanding graphene device

•Transfer/contamination/physical damage free one-pot growth of QFSG/vicinal SiC heterostructure.•Achieved 20-fold enhanced photoresponse on AuNP-assisted QFSG/vicinal SiC.•QFSG device with low-bias voltage achieved higher photoresponsivity (60.8 mA/W) than existing devices (0.2 to 20 mA/W) at 10 mV.•Gateless QFSG/vicinal SiC achieved 30-fold increment in photodetection response than EG/SiC device.•Demonstrated self-powered QFSG/vicinal SiC photodetector with high photoresponsivity.