Dark current reduction and operational wavelength shift in normal incidence InAs-GaAs QDIPs through the introduction of AlGaAs layers in the active region of the detector

Self-assembled quantum dots (SAQDs) are an attractive alternative to quantum wells (QWs) for near to long-wavelength infrared photodetector applications. Due to the 3D carrier confinement and lack of symmetry-imposed selection rules, SAQDs are intrinsically sensitive to normal incidence photoexcitation and predicted to have lower dark current and higher sensitivity compared to QW intersubband photodetectors (Ryzhii, 1996), though the filling factor is substantially less for QDs than that for QWs. Initial reported results on normal-incidence QD intersubband photodetectors (e.g. Pan et al, 1998) offer encouragement for further investigations. In this report, we demonstrate the ability to reduce the dark current and to shift the operational wavelength of InAs-GaAs QD infrared photodetectors (QDIPs) through the introduction of AlGaAs barriers in the active region of the detector structure. AlGaAs layers are placed between the QD layers to act as blocking barriers for the dark current contribution through the region between the QDs.