Spectral broadening due to post-growth annealing of a long-wave InGaAs/GaAs quantum dot infrared photodetector with a quaternary barrier layer

• Spectral broadening due to ex-situ annealing on InGaAs quantum dot detector
• Dark current density was decreased for 650 °C annealed device compared to as-grown.
• Noise current initially decreased for 650 °C annealed device compared to un-annealed.
• Three-time increment in responsivity is noted for 650 °C annealed device.
• Passivation of as-grown defect by annealing predicted the reason of improvement.

We present the effect of post-growth rapid thermal annealing on multilayer, uncoupled In0.50Ga0.50As/GaAs quantum dot infrared photodetectors (QDIPs) with a combination of quaternary In0.21Al0.21Ga0.58As and GaAs capping. Long wave photoresponse (~ 0.11 eV or 10.2 μm) with narrow spectral width (14%) is obtained from as-grown QDIPs. The spectral width increases to 45% for QDIP annealed at 800 °C. It is likely that a large inter-diffusion effect because of annealing changes the composition of the quantum dots and capping layer, thus increasing the QDIP spectral width. Dark current as well as noise current is decreased for 650 °C annealed QDIP compared to as-grown detector. Passivation of as-grown defect by post growth annealing predicted the improvement of dark current. Such improvement and broadening of characteristics may render such QDIPs suitable for use in broadband infrared imaging applications.