In this paper, we report reduced dark current quantum dot (QD) photodetectors (PDs) grown on Si(001) substrate by spatially separated co-doping technique, including n-type direct doping in QDs and p-type modulation doping in barrier layers. The absorption region of the QD PDs consists of eight stacked QD layers. Compared with the p-doped PDs, the co-doped PDs achieve a record-low dark current of 0.91 pA and a higher photocurrent because of additional electrons effectively passivating the defects by n-type doping. Furthermore, the co-doping technique provides two different types of impurities, which generates a stronger built-in electric field in the QDs and thereby increases the maximum 3 dB bandwidth of the QD PDs.
Wang et al. (2026) studied this question.