Electrode-induced lattice distortions in GaAs multi-quantum-dot arrays
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Electrode-induced lattice distortions in GaAs multi-quantum-dot arrays Anastasios Pateras1,a) , Jérôme Carnis2 , Uditendu Mukhopadhyay3, Marie-Ingrid Richard2 , Steven J. Leake4, Tobias U. Schülli4, Christian Reichl5, Werner Wegscheider5, Juan Pablo Dehollain3, Lieven M.K. Vandersypen3, Paul G. Evans1 1
Department of Materials Science & Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA Aix Marseille Université, CNRS, IM2NPUMR 7334, Université de Toulon, Marseille 13397, France; and ID01/ESRF, F-38043 Grenoble Cedex, France 3 QuTech and Kavli Institute of NanoScience, Delft University of Technology, Delft 2600 GA, The Netherlands 4 ID01/ESRF, F-38043 Grenoble Cedex, France 5 Laboratory for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland a) Address all correspondence to this author. e-mail: [email protected] 2
Received: 20 September 2018; accepted: 5 February 2019
Increasing the number of quantum bits while preserving precise control of their quantum electronic properties is a significant challenge in materials design for the development of semiconductor quantum computing devices. Semiconductor heterostructures can host multiple quantum dots that are electrostatically defined by voltages applied to an array of metallic nanoelectrodes. The structural distortion of multiple-quantum-dot devices due to elastic stress associated with the electrodes has been difficult to predict because of the large micrometer-scale overall sizes of the devices, the complex spatial arrangement of the electrodes, and the sensitive dependence of the magnitude and spatial variation of the stress on processing conditions. Synchrotron X-ray nanobeam Bragg diffraction studies of a GaAs/AlGaAs heterostructure reveal the magnitude and nanoscale variation of these distortions. Investigations of individual linear electrodes reveal lattice tilts consistent with a 28-MPa compressive residual stress in the electrodes. The angular magnitude of the tilts varies by up to 20% over distances of less than 200 nm along the length of the electrodes, consistent with heterogeneity in the metal residual stress. A similar variation of the crystal tilt is observed in multiple-quantumdot devices, due to a combination of the variation of the stress and the complex electrode arrangement. The heterogeneity in particular can lead to significant challenges in the scaling of multiple-quantum-dot devices due to differences between the charging energies of dots and uncertainty in the potential energy landscape. Alternatively, if incorporated in design, stress presents a new degree of freedom in device fabrication.
Introduction Semiconductor electronic devices exploiting the confinement of electrons with well-defined quantum states present a promising route toward computing systems that can solve problems that are not within the capabilities of classical computers [1]. Examples include solutions to problems that become intractable for large numbers or for complex systems, as, for example, in the use of Shor’s algorithm to find the prime fa
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