Seminar by Prof. Marco Felici
Title: Hydrogen engineering of semiconductors: quantum emitters, two-dimensional nanostructures, and Berry-phase photonics
Speaker: Prof. Marco Felici, Sapienza University of Rome, Italy
Abstract: Advanced nanophotonics requires nm-scale control of optoelectronic properties and quantum-emitter positioning within the fabricated devices [1,2]. Hydrogen, long known to modify the optical and electrical properties of semiconductors by passivating defects [3], offers a remarkably versatile means of achieving this control.
In dilute-nitride semiconductors such as GaAsN and GaPN, H irradiation forms N–H complexes that neutralize the effects of nitrogen incorporation [4]. In GaAsN, the resulting reopening of the energy gap enables the fabrication of site-controlled, single-photon-emitting quantum dots through spatially selective hydrogenation or local H removal [5,6], as well as their integration into photonic-crystal cavities [5]. H-induced changes in the lattice parameter can also generate the controlled distortions required to trigger the Berry-phase X-ray translation effect [7]. Using ordered arrays of selectively hydrogenated GaAsN/GaAsN:H dots, we recently measured lateral X-ray beam translations exceeding 100 μm and, through comparison with finite-element simulations, established a predictive framework for controlling X-ray propagation [8].
While the phenomena observed in hydrogenated dilute nitrides are notable in their own right, the effects of H irradiation on van der Waals (vdW) materials may be even more striking. In transition-metal dichalcogenides (TMDCs), hydrogen accumulates as H 2 in the first interlayer region, producing monolayer-thick domes that locally transform the otherwise optically inactive bulk crystal into an efficient light emitter [9]. In hexagonal boron nitride (hBN), H irradiation similarly produces highly strained, H 2 -filled domes [10]. The nonuniform strain fields hosted by TMDC domes profoundly reshape their band structure, producing a direct-to-indirect band-gap transition from the dome edge to its apex [11]. Lithographically positioned, hBN-capped TMDC domes can also host spatially controlled single-photon emitters [12].
Finally, the possibility of combining vdW heterostructuring with H-assisted strain engineering can unlock intriguing new functionalities and physical phenomena. InSe/TMDC dome heterostructures provide a powerful demonstration of this approach, in which strain-activated carrier transfer enhances the emission efficiency of InSe by up to two orders of magnitude [13]. Taken together, these results illustrate the versatility of hydrogen engineering for quantum-light sources and strain-engineered heterostructures, while opening prospects for extending Berry-phase photonics to vdW materials.
References:
[1] Y. Akahane et al., Nature 425, 944 (2003).
[2] K. Hennessy et al., Nature 445, 896 (2007).
[3] S. J. Pearton et al., Hydrogen in Crystalline Semiconductors (Springer, Berlin, 1992).
[4] G. Pettinari et al., Nanotechnology 32, 185301 (2021).
[5] M. Felici et al., Phys. Rev. B 101, 205403 (2020).
[6] F. Biccari et al., Adv. Mater. 30, 1705450 (2018).
[7] Y. Kohmura et al., Phys. Rev. Lett. 110, 057402 (2013).
[8] M. Felici et al., Adv. Mater. 38, e13259 (2026).
[9] D. Tedeschi et al., Adv. Mater. 31, 1903795 (2019).
[10] E. Blundo et al., Nano Lett. 22, 1525 (2022).
[11] E. Blundo et al., Phys. Rev. Research 2, 012024 (2020).
[12] S. Cianci et al., Adv. Opt. Mater. 11, 2202953 (2023).
[13] E. Blundo et al., Nano Lett. 25, 3375 (2025).