Influence of molecular beam effusion cell quality on optical and electrical properties of quantum dots and quantum wells

Nguyen, G.N. and Korsch, A.R. and Schmidt, M. and Ebler, C. and Labud, P.A. and Schott, R. and Lochner, P. and Brinks, F. and Wieck, A.D. and Ludwig, Ar.

Volume: 550 Pages:
DOI: 10.1016/j.jcrysgro.2020.125884
Published: 2020

Quantum dot heterostructures with excellent low-noise properties became possible with high purity materials recently. We present a study on molecular beam epitaxy grown quantum wells and quantum dots with a contaminated aluminum evaporation cell, which introduced a high amount of impurities, perceivable in anomalies in optical and electrical measurements. We describe a way of addressing this problem and find that reconditioning the aluminum cell by overheating can lead to a full recovery of the anomalies in photoluminescence and capacitance–voltage measurements, leading to excellent low noise heterostructures. Furthermore, we propose a method to sense photo-induced trap charges using capacitance–voltage spectroscopy on self-assembled quantum dots. Excitation energy-dependent ionization of defect centers leads to shifts in capacitance–voltage spectra which can be used to determine the charge density of photo-induced trap charges via 1D band structure simulations. This method can be performed on frequently used quantum dot diode structures. © 2020 Elsevier B.V.

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