Why QDIPs are still inferior to QWIPs: Theoretical analysis

As predicted theoretically, quantum dot infrared photodetectors (QDIPs) can substantially surpass quantum well infrared photodetectors (QWIPs). Recently, a number of research groups reported fabrication and extensive experimental investigation of various InAs/GaAs, InGaAs/GaAs, and InGaAs/InGaP QDIPs. However, most of the fabricated QDIPs have worse performance than QWIPs. To answer the questions why QDIPs are still inferior to QWIPs and how to improve them, we analyze the QDIP operation using the developed device model of QDIPs with realistic parameters. The model takes into account the main physical factors determining the operation of QDIPs. We calculate the dark current and the responsivity of QDIPs as functions of their structural parameters, the applied voltage, and temperature. The calculated characteristics are in agreement with those of realistic QDIPs studied experimentally. The revealed relations between the QDIP operation characteristics and structural parameters explain the main features of QDIPs observed in experiments. We estimate the QDIP detectivity and find the conditions for its maximum value. We compare the QDIP characteristics with those of QWIPs.