Quantum Confined Stark Effect In Type II Nanoscale Heterostructures For Tunable Photonic Devices

Abstract

The Quantum Confined Stark Effect (QCSE) offers a powerful route to electrically tune the optical response of semiconductor nanostructures, enabling next-generation photonic devices. However, type-I systems suffer from limited carrier separation, reducing tunability. To address this, our work investigates type-II InAs/GaSb multiple quantum wells (MQWs), where electrons and holes are spatially separated, enhancing QCSE. A semi-empirical model was employed, supported by epitaxial growth and structural characterization, to analyze thicknesses ranging from 5–15 nm under applied fields up to 200 kV/cm. The methodology combined band-structure modeling, Gaussian absorption simulations, and Monte-Carlo sensitivity analysis. Results show that wavelength redshift increases strongly with thickness, from Δλ ≈ 0.26 µm at 5 nm to Δλ ≈ 0.55 µm at 15 nm. Oscillator strength decays exponentially with field, dropping from f₀ = 0.8 at 5 nm to 0.27 at 15 nm, with further suppression under 200 kV/cm. Meanwhile, exciton lifetime rises from ~3.3 ns (5 nm) to ~7.0 ns (15 nm). The contour mapping confirms tunability up to 0.7 µm. These findings demonstrate a trade-off: thicker wells maximize tuning but reduce absorption efficiency. This balance provides clear design guidelines for optimized tunable modulators and mid-IR photonic devices.