Excited states of InAs quantum dots (QDs) can be energetically coupled with the confined level of GaAs quantum wells (QWs) in a thin-barrier resonant tunneling diode (RTD).Single charge variation in the coupled QD can effectively switch on/off the resonant tunneling current passing through RTD,not only for efficient single-photon detection but also for photon-number-resolving detection.We present the study of the QD QW coupling effect in the quantum dot coupled resonant tunneling diode (QD-cRTD) and figure out important factors for further improving the detector performance.