Analysis of strain relaxation and dark current minimization in In(Ga)As QDIP with In0.15Ga0.85As/GaAs capping

Quantum dot infrared photodetectors (QDIPs) with different dot materials have been investigated in this study to analyze the optical, structural and electrical behavior. The InAs and In_0.5Ga_0.5As QDIPs comprise ten vertically-stacked uncoupled quantum dot (QD) layers with In_0.15Ga_0.85As/GaAs capping, whereas the overgrowth percentage in both the dot materials has been kept similar (~59%). The InGaAs QDIP has a red shifted photoluminescence spectra compared to the InAs QDIP along with a lower full width at half maxima (FWHM) and higher activation energy. This attributes the formation of dots with larger size and higher vertical barrier potential in the InGaAs QDIP heterostructure. The lattice mismatch between the dot and its underlying/capping layer is less in the InGaAs QDs, which has been observed from the HRXRD rocking-curve analysis. The average strain obtained in the InGaAs QD is less compared to the InAs QD. Moreover, a reduced dark current density has been obtained in the InGaAs QDIP compared to the InAs QDIP at room temperature. Both the QDIPs have their spectral response in the mid-infrared range. However, the InGaAs QDIP has peaks with lower FWHM due to minimized dot size dispersion in the structure.