Marianne Bathen

Last Name

Bathen

First Name

Marianne

ORCID

0000-0002-6269-3530

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Publications 1 - 10 of 15

Depth-Resolved Study of the SiO2- SiC Interface Using Low-Energy Muon Spin Rotation Spectroscopy
Kumar, Piyush; Martins, Maria Inês M.; Bathen, Marianne; et al. (2022)
Materials Science Forum
In this work, the interface between 4H-SiC and thermally grown SiO2 is studied using low energy muon spin rotation (LE-μSR) spectroscopy. Samples oxidized at 1300 °C were annealed in NO or Ar ambience and the effect of the ambience and the annealing temperature on the near interface region is studied in a depth resolved manner. NO-annealing is expected to passivate the defects, resulting in reduction of interface traps, which is confirmed by electrical characterization. Introduction of N during annealing, to the SiC matrix, results in a thin, carrier rich region close to the interface leading to an increase in the diamagnetic asymmetry. Annealing in an inert environment (Ar) seems to have much lesser impact on the electrical signal, however the μSR shows a reduced paramagnetic asymmetry, indicating a narrow region of low mobility at the interface.
Characterization methods for defects and devices in silicon carbide
Bathen, Marianne; Lew, Christopher T.-K.; Woerle, Judith; et al. (2022)
Journal of Applied Physics
Significant progress has been achieved with silicon carbide (SiC) high power electronics and quantum technologies, both drawing upon the unique properties of this material. In this Perspective, we briefly review some of the main defect characterization techniques that have enabled breakthroughs in these fields. We consider how key data have been collected, interpreted, and used to enhance the application of SiC. Although these fields largely rely on separate techniques, they have similar aims for the material quality and we identify ways in which the electronics and quantum technology fields can further interact for mutual benefit.
Electrically active defects induced by thermal oxidation and post-oxidation annealing of n-type 4H-SiC
Kumar, Piyush; Bathen, Marianne; Martins, Maria I.M.; et al. (2024)
Journal of Applied Physics
In this work, we have performed a detailed study of the defects created in the bulk of 4H-SiC after thermal oxidation and post oxidation annealing using deep level transient spectroscopy and minority carrier transient spectroscopy (MCTS). The study reveals the formation of several shallow and deep level majority carrier traps in the bandgap. The ON1 (EC - 0:85 eV), ON2a (EC - 1:05 eV), and ON2b (Ec - 1:17 eV) levels are the most dominant and are observed across all the samples (EC denotes the conduction band edge). Three shallow levels Ti(k) (EC - 0:17 eV), E0:23 (EC - 0:23 eV), and C1=2 (EC - 0:36=0:39 eV) are observed in the samples. For most of the majority carrier defects, the highest concentration is observed after an NO anneal at 1300 C. This behavior is sustained in the depth profile measurements where the defect concentration after the NO anneal at 1300 C is significantly higher than for the rest of the samples. The origin of most of the majority carrier defects has been attributed to C interstitial injection from the interface during thermal oxidation and annealing. MCTS measurements reveal two prominent minority carrier traps, labeled O0:17 (EV þ 0:17 eV) and B (EV þ 0:28 eV), where the concentration of O0:17 is independent of annealing parameters while the concentration of the B level increases after the NO anneal (EV denotes the valence band edge). Furthermore, the depth profiles of the defects are used to evaluate their diffusion parameters by solving the diffusion equation to fit the experimental profiles. The defect concentrations decay exponentially with depth, which evidences that the defects were created at or near the SiO2–SiC interface and migrate toward the bulk during oxidation and post-oxidation annealing.
Dual configuration of shallow acceptor levels in 4H-SiC
Bathen, Marianne; Kumar, Piyush; Ghezellou, Misagh; et al. (2024)
Materials Science in Semiconductor Processing
Acceptor dopants in 4H-SiC exhibit energy levels that are located deeper in the band gap than the thermal energy at room temperature (RT), resulting in incomplete ionization at RT. Therefore, a comprehensive understanding of the defect energetics and how the impurities are introduced into the material is imperative. Herein, we study impurity related defect levels in 4H-SiC epitaxial layers (epi-layers) grown by chemical vapor deposition (CVD) under various conditions using minority carrier transient spectroscopy (MCTS). We find two trap levels assigned to boron impurities, B and D, which are introduced to varying degrees depending on the growth conditions. A second acceptor level that was labeled X in the literature and attributed to impurity related defects is also observed. Importantly, both the B and X levels exhibit fine structure revealed by MCTS measurements. We attribute the fine structure to acceptor impurities at hexagonal and pseudo-cubic lattice sites in 4H-SiC, and tentatively assign the X peak to Al based on experimental findings and density functional theory calculations.
Insights into the oxidation of SiC from a deep potential model
Kälin, Colin; Bathen, Marianne; Grossner, Ulrike; et al. (2024)
Exploring the border traps near the valence band in the SiO2-SiC system using above-band-gap optical excitation
Kumar, Piyush; Goncalves de Medeiros, Helton; Race, Salvatore; et al. (2024)
Physical Review Applied
Studying near-valence-band (EV) defects at the insulator–n-type 4H-SiC interface is challenging due to the low minority carrier concentration. Herein, we present a technique for characterizing the border traps near EV in an n-type 4H-SiC MOS capacitor by generating holes using above-band-gap optical excitation (OE). A rise in capacitance was observed under OE (due to hole capture by border traps), remaining stable long after the optical stimulus was removed, resulting in a persistent photocapacitance effect. We show the dynamics of the capture process and perform a quantification of the captured holes in samples with thermally grown oxide and different postoxidation annealing treatments.
Mapping the impact of defect distributions in silicon carbide devices using the edge transient-current technique
Dorfer, Christian; Bathen, Marianne; Race, Salvatore; et al. (2023)
Applied Physics Letters
We demonstrate that the multi-photon absorption edge transient-current technique (edge-TCT) can be used to three-dimensionally map the impact of defect distributions on device characteristics in situ inside the bulk of silicon carbide devices. A ∼5 μm wide defect-rich layer induced by proton irradiation at a depth of ∼27 μm was investigated in 4H-SiC samples and compared to the pristine case. Edge-TCT enables mapping of the position of the implantation peak as well as to identify the space charge polarity around the implanted region. The edge-TCT results are compared to Monte Carlo simulations of the proton irradiation that were verified by luminescence measurements and TCAD-based device simulations. In result, edge-TCT is found to be capable of distinguishing different device regions due to its charge sensitivity and directly visualizing space charge regions, facilitating calibration of charge carrier distribution models in semiconductor devices.
Heavy-Ion-Induced Defects in Degraded SiC Power MOSFETs
Martinella, Corinna; Bathen, Marianne; Javanainen, Arto; et al. (2023)
Materials Science Forum ~ Silicon carbide MOSFETs and special materials : special topic volume with invited peer-reviewed papers only
Cathodoluminescence spectroscopy is used to investigate the formation of point- and extended defects in SiC power MOSFETs exposed to heavy-ions. Devices showing single event leakage current (SELC) effects are analysed and compared to pristine samples. Common luminescence peaks of defect centers localized in the thermal-SiO2 are identified, together with peaks at the characteristic wavelength of extended defects.
Impact of carbon injection in 4H-SiC on defect formation and minority carrier lifetime
Bathen, Marianne; Karsthof, Robert; Galeckas, Augustinas; et al. (2024)
Materials Science in Semiconductor Processing
Point defects in silicon carbide (SiC) can act as charge carrier traps and have a pronounced impact on material properties such as the mobility and carrier lifetime. Prominent among these traps is the carbon vacancy (VC) with a demonstrated detrimental effect on the minority carrier lifetime in 4H-SiC epitaxial layers. Hence, a variety of methods for VC removal have been proposed. Common to all is that they involve some sort of C-injection into the epi-layer that leads to annihilation of VC with C interstitials (Ci) via the reaction Ci＋ VC →0̸. However, many studies on injection of Ci for removal of VC do not take into account the potential effect of any additional defects that are formed as a result of excess C in the material, including electrically active defects that introduce energy levels in the SiC band gap. Herein, we study the formation and impact of carbon related defects that are introduced in 4H-SiC epi-layers by injection of excess carbon. C-injection is achieved by annealing 4H-SiC epi-layers covered by a graphitized photoresist known as a C-cap at 1250 °C for different durations. The resulting appearance of defects in the samples is monitored using deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) measurements, which reveal the formation of both minority and majority carrier traps as a result of the C-injection. Intriguingly, the injected carbon is also found to interact with a perennially present impurity in 4H-SiC epi-layers and a potentially lifetime limiting defect, namely boron. Furthermore, we monitor the minority carrier lifetime as a function of C-injection time and depth from the surface using cross-sectional time-resolved photoluminescence (TRPL) measurements. Both the defect distributions and the minority carrier lifetime are found to depend strongly on the duration of the C-cap anneal, with a marked depth dependence being present for all samples studied. The moderate temperature C-cap annealing treatment is proposed as a method for enhancing the carrier lifetime in n-type 4H-SiC epi-layers for power device applications.
Investigation of Electrically Active Defects in SiC Power Diodes Caused by Heavy Ion Irradiation
Für, Natalija; Belanche Guadas, Manuel; Martinella, Corinna; et al. (2023)
IEEE Transactions on Nuclear Science
Deep-level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) are used to investigate electrically active defects in commercial silicon carbide (SiC) Schottky power diodes after heavy-ion microbeam irradiation at different voltages. The DLTS and MCTS spectra of pristine samples are analyzed and compared to devices showing or not signatures of single event leakage current (SELC) degradation. An additional peak labeled 'C' with an activation energy of 0.17 eV below the conduction band edge is observed in the DLTS spectra of a sample degraded with SELC.

Publications 1 - 10 of 15

Marianne Bathen

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