Passivation of Si, Ge and SiGe Surfaces by ALD Nanolayers

For many (opto)electronic devices, it is vital to reduce the recombination of charge carriers at the semiconductor surfaces and interfaces. This is becoming more and more challenging due to the ongoing diversification in semiconductor materials to be used in the devices but also due to the increasing surface-to-volume ratio of the (nano)structures employed in electronics and photonics. Surface passivation can be achieved by employing ultrathin films of semiconductor or dielectric materials which often serve other functionalities in the devices too. The underlying mechanism of the surface passivation can be the reduction of surface defect states (i.e., so-called chemical passivation) and/or band bending due to so-called field-effect passivation effect (e.g., due to fixed charges in the film).<br/>In this contribution the surface passivation by some innovative nanolayer approaches prepared by atomic layer deposition (ALD) will be presented. The focus will be on Si and Ge surfaces and also include hexagonal SiGe alloy nanowires which are of interest for nanolasers due to their direct-bandgap [1]. The nanolayers include materials such as Al₂O₃, PO_x and (doped) ZnO as well as stacks thereof [2,3,4,5]. Special attention will be given to the underlying mechanism of the surface passivation achieved as well as its relation to the properties of the nanolayers employed.<br/><br/>[1] E. M. T. Fadaly, A. Dijkstra, J.R. Suckert, D. Ziss, M. A. J. van Tilburg, C. Mao, Y. Ren, V.T. van Lange, K. Korzun, S. Kölling, M. A. Verheijen, D. Busse, C. Rödl, J. Furthmüller, F. Bechstedt, J. Stangl, J.J. Finley, S. Botti, J. E. M. Haverkort, E. P. A. M. Bakkers, Nature 580, 205 (2020).<br/>[2] W. J. H.Berghuis, J. Melskens, B. Macco, R. J. Theeuwes, L. E. Black, M. A. Verheijen, W. M. M. Kessels, J. Appl. Phys. 130, 135303 (2021).<br/>[3] R. J. Theeuwes, W.J.H. Berghuis, B. Macco, W. M. M. Kessels, Appl. Phys. Lett. 123, 091604 (2023).<br/>[4] W. J. H. Berghuis, M. A. J. van Tilburg, W. H. J. Peeters, V. T. van Lange, E. M. T. Fadaly, E. C. M. Renirie, R. J. Theeuwes, M. A. Verheijen, B. Macco, E. P. A. M. Bakkers, J. E. M. Haverkort, W. M. M. Kessels, to be published.<br/>[5] B. Macco, M.L. van de Poll, B.W.H. van de Loo, T.M.P. Broekema, S.B. Basuvalingam, C.A.A. van Helvoirt, W.J.H. Berghuis, R.J. Theeuwes, N. Phung, and W.M.M. Kessels, Sol. Energy Mater. Solar Cells, 245, 111689 (2022).