Barrier engineered superlattice and quantum dot detectors for HOT operation

Abstract

In this paper, we demonstrate a high operating temperature (HOT) quantum dot-in-a-well (DWELL) infrared photodetector with enhanced normal incidence (s-polarization) radiation photocurrent. The s-to-p polarization ratio was increased to 50%, compared to the 20% in conventional quantum dot detectors. This improvement was achieved through engineering the dot geometry and the quantum confinement via post growth capping materials of the quantum dots (QDs). The effect of the capping procedures was determined by examining the dot geometry using transmission electron microscopy (TEM) and s-to-p polarization induced photocurrent in the DWELL structure photodetector. The TEM image shows a quantum dot with a reduced base of 12 nm and an increased height of 8 nm. The infrared photodetectors fabricated from this material shows a peak photodetectivity of 1×109 cmHz1/2/W at 77K for a peak wavelength of 4.8 μm and 1×107 cmHz1/2/W at 300K for a peak wavelength of 3.2 μm. The dark current density is as low as 2×10-4A/cm2 and the photocurrent gain is 100 at the optimal operating bias.