Amanda Langørgen

• Langørgen, Amanda; Frodason, Ymir Kalmann; Jensen, Ingvild Julie Thue; Turiansky, Mark E.; Walle, Chris G. Van de & Vines, Lasse (2025). Formation of the E4* level in implanted β-Ga2O3. PHYSICAL REVIEW MATERIALS. 9. doi: 10.1103/3ktr-6kmw. Fulltekst i vitenarkiv
• Langørgen, Amanda; Vines, Lasse & Frodason, Ymir Kalmann (2024). Perspective on electrically active defects in β- Ga2O3 from deep-level transient spectroscopy and first-principles calculations. Journal of Applied Physics. ISSN 0021-8979. 135(19). doi: 10.1063/5.0205950. Fulltekst i vitenarkiv Vis sammendrag

  The ultra-wide bandgap of gallium oxide provides a rich plethora of electrically active defects. Understanding and controlling such defects is of crucial importance in mature device processing. Deep-level transient spectroscopy is one of the most sensitive techniques for measuring electrically active defects in semiconductors and, hence, a key technique for progress toward gallium oxide-based components, including Schottky barrier diodes and field-effect transistors. However, deep-level transient spectroscopy does not provide chemical or configurational information about the defect signature and must, therefore, be combined with other experimental techniques or theoretical modeling to gain a deeper understanding of the defect physics. Here, we discuss the current status regarding the identification of electrically active defects in beta-phase gallium oxide, as observed by deep-level transient spectroscopy and supported by first-principles defect calculations based on the density functional theory. We also discuss the coordinated use of the experiment and theory as a powerful approach for studying electrically active defects and highlight some of the interesting but challenging issues related to the characterization and control of defects in this fascinating material.

• Langørgen, Amanda; Frodason, Ymir Kalmann; Karsthof, Robert Michael; Wenckstern, Holger Von; Jensen, Ingvild Julie Thue & Vines, Lasse [Vis alle 7 forfattere av denne artikkelen] (2023). Defect level in κ-Ga2O3 revealed by thermal admittance spectroscopy. Journal of Applied Physics. ISSN 0021-8979. 134(1), s. 015701-1–015701-6. doi: 10.1063/5.0150994. Fulltekst i vitenarkiv Vis sammendrag

  Defects in pulsed-laser deposition grown have been investigated using thermal admittance spectroscopy and secondary ion mass spectrometry (SIMS). A film was grown on either a tin-doped indium oxide or an aluminum-doped zinc oxide buffer layer on a sapphire substrate functioning as back contact layer in vertical diode structures. In both sample types, a distinct signature in the capacitance signal was observed in the temperature range of 150–260 K. The corresponding defect charge-state transition level, labeled ⁠, was found to exhibit an activation energy of 0.21 eV. Potential candidates for the level were investigated using a combination of SIMS and hybrid-functional calculations. SIMS revealed the main impurities in the sample to be tin, silicon, and iron. The hybrid-functional calculations predict the acceptor levels of substitutional iron to lie 0.7–1.2 eV below the conduction band minimum depending on Ga-site, making an unlikely candidate for the level. Furthermore, Si as well as Sn substituting on the sixfold coordinated Ga2 site and the fivefold coordinated Ga3 and Ga4 sites are all shallow donors in -⁠, similar to that of -⁠. Sn substituting on the fourfold Ga1 site is, however, predicted to have levels in the bandgap at 0.15 and 0.24 eV below the conduction band minimum, in accordance with the extracted activation energy for ⁠. Thus, we tentatively assign as the origin of the level.

• Polyakov, A.Y.; Kochkova, A.I.; Langørgen, Amanda; Vines, Lasse; Vasilev, A. & Shchemerov, I.V. [Vis alle 8 forfattere av denne artikkelen] (2023). On the possible nature of deep centers in Ga2O3. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 41(2), s. 023401-1–023401-6. doi: 10.1116/6.0002307. Fulltekst i vitenarkiv Vis sammendrag

  The electric field dependence of emission rate of the deep traps with level near Ec−0.6 eV, so-called E1 traps, was studied by means of deep level transient spectroscopy measurements over a wide range of applied voltages. The traps were initially introduced by 900 °C ampoule annealing in molecular hydrogen. The results indicate the activation energy of the centers and the ratio of high-field to low-field electron emission rates at a fixed temperature scale as the square root of electric field, suggesting that the centers behave as deep donors. The possible microscopic nature of the centers in view of recent theoretical calculations is discussed. The most likely candidates for the E1 centers are SiGa1–H or SnGa2–H complexes.

• Langørgen, Amanda; Zimmermann, Christian; Frodason, Ymir Kalmann; Verhoeven, Espen Førdestrøm; Weiser, Philip Michael & Karsthof, Robert Michael [Vis alle 8 forfattere av denne artikkelen] (2022). Influence of heat treatments in H2 and Ar on the E1 center in β-Ga2O3. Journal of Applied Physics. ISSN 0021-8979. 131(115702). doi: 10.1063/5.0083861. Fulltekst i vitenarkiv Vis sammendrag

  The influence of heat treating [Formula: see text]-type bulk [Formula: see text]-Ga[Formula: see text]O[Formula: see text] in hydrogen (H[Formula: see text]) and argon (Ar) gases on the presence of the defect level commonly labeled as [Formula: see text] was studied. Fourier transform-infrared spectroscopy confirms that hydrogen (H) is incorporated into [Formula: see text]-Ga[Formula: see text]O[Formula: see text] during H[Formula: see text] annealing at 900 °C. Deep-level transient spectroscopy measurements reveal that the concentration of the [Formula: see text] level is promoted by the introduction of H, in contrast to what is observed in samples heat-treated in an Ar flow. We further find the [Formula: see text] level to be stable against heat treatments at 650 K, both with and without an applied reverse-bias voltage. Potential candidates for the defect origin of [Formula: see text] are investigated using hybrid-functional calculations, and three types of defect complexes involving H are found to exhibit charge-state transition levels compatible with [Formula: see text], including substitutional H at one of the threefold coordinated O sites, Ga-substitutional shallow donor impurities passivated by H, and certain configurations of singly hydrogenated Ga–O divacancies. Among these types, only the latter exhibit H binding energies that are consistent with the observed thermal stability of [Formula: see text].

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• Langørgen, Amanda; Frodason, Ymir Kalmann; Zimmermann, Christian; Karsthof, Robert Michael; Weiser, Philip Michael & Jensen, Ingvild Julie Thue [Vis alle 7 forfattere av denne artikkelen] (2025). Seminar talk - Electrically active defects in β-Ga2O3. Fulltekst i vitenarkiv
• Langørgen, Amanda; Frodason, Ymir Kalmann; Jensen, Ingvild Julie Thue & Vines, Lasse (2024). A metastable deep defect in β-Ga2O3. Fulltekst i vitenarkiv
• Langørgen, Amanda; Frodason, Ymir Kalmann; Jensen, Ingvild Julie Thue & Vines, Lasse (2023). A metastable deep defect in beta-Ga2O3. Fulltekst i vitenarkiv
• Langørgen, Amanda; Frodason, Ymir Kalmann; Karsthof, Robert Michael; Wenckstern, Holger von; Jensen, Ingvild Thue & Vines, Lasse (2022). An electron trap in κ-Ga2O3 and the quest for its microscopic origin. Fulltekst i vitenarkiv
• Olsen, Vegard Skiftestad; Karlsen, Kjetil; Langørgen, Amanda; Andreassen, Magnus & Hommedal, Ylva Knausgård (2021). Omvisning UiO MiNaLab for FA bachelorstudenter. Fulltekst i vitenarkiv
• Langørgen, Amanda; Karsthof, Robert Michael; Weiser, Philip Michael; Cavani, Olivier; Grasset, Romain & Frodason, Ymir Kalmann [Vis alle 8 forfattere av denne artikkelen] (2021). Steady-state Photocapacitance Spectroscopy of Intrinsic Defects in Electron-Irradiated β-Ga₂O₃. Fulltekst i vitenarkiv
• Zimmermann, Christian; Frodason, Ymir Kalmann; Varley, Joel Basile; Verhoeven, Espen Førdestrøm; Rønning, Vegard & Weiser, Philip Michael [Vis alle 15 forfattere av denne artikkelen] (2021). Identification of Fe-, Ti- and H-related Charge-state Transition Levels in β-Ga2O3. Fulltekst i vitenarkiv
• Langørgen, Amanda (2026). Electrical characterization of point defects in β-Ga2O3 and κ-Ga2O3. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  The semiconductor gallium oxide has received considerable attention as a next-generation material for efficient power-conversion devices. The material can exist in several crystal structures. Until now, the most stable β phase of gallium oxide has received the most focus. However, the κ phase is now also gaining attention due to a predicted large polarization which makes it attractive for specific devices that can exploit this property. Point defects – atomic-scale imperfections in the crystal lattice – significantly influence the electronic properties of semiconductors, so understanding and controlling them is essential for device realization. This thesis investigates point defects in both the β and κ phases of gallium oxide using electrical defect spectroscopy techniques. By combining these techniques with complementary measurements, treatments, and theoretical calculations, the work seeks to improve the understanding of point defects in the β phase, as well as in the less studied κ phase. Combined, this work contributes to further maturing the semiconductor material gallium oxide.

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