Vertically Coupled Hybrid InAs Sub-Monolayer on InAs Stranski–Krastanov Quantum Dot Heterostructure: Toward Next Generation Broadband IR Detection

In the present article, we are introducing a novel heterogeneously coupled InAs Submonolayer (SML) on Stranski-Krastanov (SK) quantum dot (QD) heterostructure with reduced strain accumulation. Theoretical comparison manifests the superiority of this hybrid SML-SK QDs over bilayer SK QDs. Photoluminescence and photoluminescence excitation spectroscopy are employed to characterize the electronic interaction and carrier tunneling in between this hybrid quantum dot assembly. Growth rate is optimized at 0.1 ML/sec. To tune the coupling, the barrier layer thickness is varied from 5 nm to 10 nm. Even up to the highest barrier thickness, no signature of SML peak is obtained in the PL response. But, PLE depicts the presence of SML peak, which is partially overlapped with the SK 2nd excited peak. The sample with 7.5 nm GaAs barrier shows perfect resonance between SML ground state and SK 2nd excited state. Based on experimental and analytical results, this SML on SK (SML-SK) configuration is compared with SK on SML (SK-SML) configuration; where SML-SK exhibits better inter dot electronic interaction than its reciprocal configuration. For ex situ tailoring of this heterogeneous electronic coupling, rapid thermal annealing has been done. It shows tunability of inter dot interaction with improved crystalline quality. Finally, we have shown a SML-SK quantum dot infrared photodetector with a broad spectral response (from SWIR to near LWIR).