简介：Millimeterandterahertzwavephotodetectorshaveawiderangeofapplications.However,thestate-of-the-arttechniqueslagfarbehindtheurgentdemandduetothestructureandperformancelimitations.Here,wereportsensitiveanddirectmillimeterandterahertzwavephotodetectionincompactInGaAs-basedsubwavelengthohmicmetal–semiconductor–metalstructures.Thephotoresponseoriginatesfromunidirectionaltransportationofnonequilibriumelectronsinducedbysurfaceplasmonpolaritonsunderirradiation.ThedetectedquantumenergiesofelectromagneticwavesarefarbelowthebandgapofInGaAs,offering,tothebestofourknowledge,anoveldirectphotoelectricconversionpathwayforInGaAsbeyonditsbandgaplimit.Theachievedroomtemperaturerisetimeandnoiseequivalentpowerofthedetectorare45μsand20pW·Hz^-1∕2,respectively,atthe0.0375THz(8mm)wave.Thedetectedwavelengthistunablebymountingdifferentcouplingantennas.Roomtemperatureterahertzimagingofmacroscopicsamplesataround0.166THzisalsodemonstrated.Thisworkopensanavenueforsensitiveandlarge-areauncooledmillimeterandterahertzfocalplanararrays.