Bandwidth enhancement in SWIR QD photodetectors via interfacial trap suppression using polymer capping layers

Abstract

Lead chalcogenide quantum dot (QD) photodetectors have attracted considerable attention due to their high specific detectivity, process compatibility on Si circuitry enabling monolithic integration, adjustable bandgap in short-wavelength infrared (SWIR) range, and low fabrication cost. However, the narrow bandwidth of QD photoconductors, primarily caused by the traps on film surfaces limits the application of high-speed photodetection. Here, we introduced polymer capping layers-poly(perfluorobutenylvinylether) (CYTOP) and poly (methyl methacrylate) (PMMA)-on PbSe QD surfaces to suppress those trap states. The CYTOP-capped PbSe QD photoconductor device exhibited high specific detectivity (D*) of 3.34 x 1011 Jones at 3 kHz, responsivity of up to 4.22 A/W, and bandwidth of up to 67.1 kHz under a 2000-nm illumination, while the uncapped device showed low D* of 1.88 x 1010 Jones at 37.7 Hz. The additional analysis demonstrated that the high bandwidth was achieved by the improved carrier mobility and lifetime induced by the surface trap suppression. Our study paves the way for the development of fast-response quantum dot photodetectors with facile polymer capping.