Internal photoemission of electrons from 2D semiconductor/3D metal barrier structures

• Published in: Journal of physics. D, Applied physics Applied physics, 2021-07, Vol.54 (29), p.295101
• Main Authors: Shlyakhov, I, Achra, S, Bosman, N, Asselberghs, I, Huyghebaert, C, Radu, I, Chai, J, Yang, M, Wang, S J, Bol, A, Iakoubovskii, K, Houssa, M, Stesmans, A, Afanas’ev, V V
• Format: Article
• Language: English
• Subjects: 2D materials; energy band alignment; internal photoemission
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/1361-6463/abfb1b

Understanding the energy alignment of electronic bands, which originate from ultrathin MoS 2 layers and metal electrodes attached to them, is crucial for the design of MoS 2 -based electronic devices. We have applied internal photoemission spectroscopy (IPE) to analyze this alignment. We demonstrate that IPE can yield the barrier heights in the metal/ two-dimensional semiconductor/insulator stacks when the top metal electrode is sufficiently thin for allowing both the photoexcitation of electrons and their transport towards the insulator. The electron barrier at the interface between Al and monolayer (1ML) of MoS 2 is estimated at 0.7 eV, and this value explains the experimentally observed attenuated quantum yield contribution from the aluminum. Based on the relative energies of the low-energy threshold position and the Fermi level of aluminum at the interface with the SiO 2 insulator, we provide a simple explanation for the observed current photoinjection at the interface between aluminum and 1ML MoS 2 .