Influence of quaternary (In0.21Al0.21Ga0.58As) capping on the performance of InAs quantum dot infrared photodetector

In this report, the performance of Quantum Dot Infrared Photodetector (QDIP) is examined in which the active layer consists of 10 layers of uncoupled InAs quantum dots (QDs) with quaternary In0.21Al0.21Ga0.58As capping. The optical, structural, and electrical properties of the QDIP is observed and compared with a sample in which the QDs are capped with binary GaAs layer. The observation of full width half maximum (FWHM) in the low-temperature photoluminescence (PL) of both sample shows a change in dot size distribution. Variation in the dot size distribution is also observed from the low temperature power dependent PL. Activation energy calculated from the temperature dependent PL indicates better carrier confinement in the structure with In_0.21Al_0.21Ga_0.58As capped QDs. This can be explained by the formation of higher barrier potential. Stain introduced due to lattice mismatch in the heterostructure is calculated from the high resolution X-ray diffraction (HRXRD) Rocking curves, which shows a relatively low value of strain in the QDIP heterostructure with In_0.21Al_0.21Ga_0.58As capping with respect to the QDIP with GaAs capping layer. A five order reduction in the dark current density is also observed form the QDIP with In_0.21Al_0.21Ga_0.58As capping due to insertion of Al in the capping layer. The dark current obtained for the In_0.21Al_0.21Ga_0.58As capped QDIP is 1.9E-5 A/cm², whereas the same for the GaAs capped QDIP is 4.91 A/cm². This attributes to the confinement enhancement in the prior QDIP heterostructure.