Near-infrared lateral photoresponse in InGaAs/GaAs quantum dots

Abstract

Infrared photodetectors with In(Ga)As quantum dot (QD) active element functioning on interband and intersubband transitions are currently actively investigated, however, the vertical sensors were mostly reported. In the current study, a multilayer In0.4Ga0.6As/GaAs QD photodetector structure allowing the lateral photocurrent detection at normal incidence has been prepared depositing top contact. In order to have a comparison, a heterostructure with only a stack of In0.4Ga0.6As/GaAs wetting layers (WL) has been grown. In-depth photoelectrical characterization shows an effective broad-band photodetection related to the interband transitions between quantum-confined levels in QDs ranging from 1.03 to 1.38 eV (0.9–1.2 μm) that covers much wider infrared range in comparison to that from WLs (1.27–1.38 eV). Photoluminescence spectroscopy confirms the existence of QD transitions, observed as intense QD emission which peaked at 1.12 eV (∼1 μm) redshifted in comparison to the WL structure. The mechanisms of photoconductivity are modelled and discussed, comparing both the structures. We also show that our QD stack has an order lower contribution from defects compared to similar QD structures investigated before. At the same time, our structures demonstrate appropriate device characteristics at room temperature, such as the wide dynamic range from 10–2 to 103 μW cm−2 and a high photoresponsivity up to 20 A W−1 at low excitation intensities over 10–2–10–1 μW cm−2, while at higher excitation intensities the responsivity is reduced, exhibiting a strong spectral dependence. Thereby, our results show that the grown multilayer In0.4Ga0.6As/GaAs QD heterostructure is of relevant interest for application in lateral QD photodetectors.