The influence of In composition on InGaAs-capped InAs/GaAs quantum-dot infrared photodetectors

The influence of an additional InGaAs-capped layer on the performance of InAs/GaAs quantum-dot infrared photodetectors (QDIPs) is investigated. For the device with a 15% InGaAs-capped layer, a significant response at 7.9 μm is observed for the QDIP device. The results suggest that with the additional InGaAs-capped layer, the detection wavelengths of the InAs/GaAs QDIPs could be shifted to a longer-wavelength infrared range. A further increase in the In composition will not help to obtain an even longer-wavelength detection, which is attributed to the cancellation of a lower InGaAs state, and InAs-QD bandgap shrinkage resulted from the relaxed compressive strains of the InGaAs layer with a higher In composition.