Charge Noise in InAs/GaAs Coupled Quantum Dot Devices

Exciton states in semiconductor quantum dots (QDs) shift their energy with electric field via the quantum-confined Stark effect, allowing detection of individual nearby charges using resonant optical excitation. Conversely, charge noise in QD devices broadens the optical transition linewidth above the lifetime-limited value. Tunnel-coupled QD pairs (CQDs) host interdot exciton states with a large electric dipole moment, resulting in higher electric field sensitivity and allowing for in-situ tuning of the transition energy over tens of meV within a charge stability plateau. We measure the photoluminescence and absorption spectra of diode-embedded InAs/GaAs CQDs at 20 K and observe interdot states with a significantly broader linewidth than the shorter-lived single-dot states, indicating spectral wandering from a noisy charge environment. We investigate defect charging mechanisms by monitoring the absorption linewidth while varying excitation conditions, including wavelength and power of the resonant laser and the effect of a second laser above the GaAs bandgap. Monte Carlo simulations of charged defects reproduce experimental observations, giving insight into their spatial distribution and dynamics.