Improvement in Performance of InAs Surface Quantum Dot Heterostructure-Based H₂S Gas Sensor by Introducing Buried Quantum Dot Layer

In this work, we have demonstrated InAs surface quantum dot (SQD)-based H2S gas sensors. The epitaxial growth of the strain-coupled and uncoupled InAs/GaAs QD heterostructures is done using the solid-source molecular beam epitaxy (MBE) tool. For both types of heterostructures, the coverage of the InAs monolayer (ML) for the SQD layer varies from 0.9 to 2 ML. The ML coverage of the buried quantum dots (BQDs) layer for the coupled heterostructures is kept constant (2.7 ML). The atomic force microscopy (AFM) results demonstrated that the coupled heterostructures have higher quantum dot (QD) density in the SQDs layer in comparison to the uncoupled one due to strain propagation from the BQDs toward the SQD layer. The sensor fabricated using the coupled heterostructure with 2 ML SQDs has demonstrated better performance than the uncoupled one for various concentrations (1-1000 ppm) of hydrogen sulfide (H 2S) gas due to inter-dot carrier tunneling between BQDs and SQDs layer. The coupled InAs gas sensor showed the best sensing properties at room temperature (45.9% sensor response at 100 ppm H2S ). We have demonstrated the selectivity of the sensor toward H 2S among various target gases like CO, CO2 , N2O , and NO 2 and the stability over a longer period of time with only 3% deviation (within acceptable limit). These findings have the potential to promote the fabrication of high-performance gas sensors using SQDs-based coupled heterostructures.