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

TL;DR

This paper investigates how the quality of the molecular beam effusion cell affects the optical and electrical properties of quantum dots and wells, demonstrating that reconditioning the cell improves heterostructure quality and proposing a new method to sense photo-induced trap charges.

Contribution

It introduces a reconditioning technique for contaminated effusion cells and a capacitance-voltage spectroscopy method to detect photo-induced trap charges in quantum dot structures.

Findings

Reconditioning aluminum cells by overheating restores optical and electrical properties.

Capacitance-voltage spectroscopy can detect photo-induced trap charges.

The proposed method is applicable to common quantum dot diode structures.

Abstract

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.