High-sensitivity mid infrared detection using photoionization of quantum dots

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We have designed and fabricated a quantum dot infrared photodetector which utilizes photoionization of quantum dots (QDs) and subsequent lateral transport of photoexcited carriers in the modulation-doped AlGaAs/GaAs two-dimensional channels. A broad photocurrent signal has been observed in the mid infrared range due to the bound-to-continuum intersubband absorption in the self-assembled InAs QDs. A very high responsivity (-5 A/W) has been realized by a long lifetime of photoexcited carriers as well as high mobility in the modulation-doped conduction channels.Towards the ultimate sensitivity photodetection, we have also made an effort to realize mid infrared photon counters by using InAs QDs. Toward this goal, we fabricated lateral single electron tunneling structures by using metallic nanogap electrodes and successfully observed a clear Coulomb blockade and a shell structure-like conductance change at 4.2 K.