In the development of radiation sensors based on MOSFET devices, the process of enhancing gate dielectric radiation response should be considered, as the gate dielectric is a sensitive area. In this study, optical and electrical characteristics of fabricated three-layered Al/Er₂O₃/Eu₂O₃/SiO₂/n-Si/Al MOS capacitors for radiation sensors were comprehensively investigated. MOS capacitors with 15 nm thin SiO₂, 25 nm thin Eu₂O_3, and 110 nm thick Er₂O₃ stacked gate oxide layers were grown on the n-Silicon substrate by thermal oxidation and electron beam evaporation systems, respectively. The aluminum gate and back contacts of the capacitors were formed by RF magnetron sputtering. The optical and electrical properties of the thin films and capacitors were analyzed by studying the reflection, transmittance, refractive index and absorption coefficient, Capacitance–Voltage, Conductance–Voltage, and Current density–Voltage measurements. It is observed from these studies that interfacial layers, which appeared to cause interfacial dipoles, are used to reduce the interface trap charge density and oxide trap charge density in order to improve the charge storage capacity of the device.

1. A. Dubey, A. Singh, R. Narang, M. Saxena, M. Gupta, "Modeling and Simulation of Junctionless Double Gate Radiation Sensitive FET (RADFET) Dosimeter," IEEE Trans. Nanotechnol., vol. 17, no. 1, pp. 49 – 55, Jan. 2018.
   DOI: 10.1109/TNANO.2017.2719286
2. A. Pon, K. S. V. P. Tulasi, R. Ramesh, "Effect of interface trap charges on the performance of asymmetric dielectric modulated dual short gate tunnel FET," Int. J. Electron. Commun., vol. 102, pp. 1 – 8, Apr. 2019.
   DOI: 10.1016/j.aeue.2019.02.007
3. Y. Li et al., "Interface and electrical properties of buried InGaAs channel MOSFET with an InP barrier layer and Al2O3/HfO2/Al2O3 gate dielectrics," Appl. Phys. Express, vol. 13, no. 1, article no. 011004, Jan. 2020.
   DOI: 10.7567/1882-0786/ab5acf
4. Y. Zheng, W. Shi, M. Wang, H. Liu, C. Zhou, "N-RADFET will able to replace P-RADFET," Int. J. Appl. Res., vol. 2, no. 5, pp. 958 – 960, 2016.
   Retrieved from: https://www.allresearchjournal.com/archives/?year=2016&vol=2&issue=5&part=N&ArticleId=2028
   Retrieved on: Jan. 10, 2020
5. M. S. Martínez-García, J. T. del Río, A. Jaksic, J. Banqueri, M. A. Carvajal, "Response to ionizing radiation of different biased and stacked pMOS structures," Sens. Actuator A Phys., vol. 252, pp. 67 – 75, Dec. 2016.
   DOI: 10.1016/j.sna.2016.11.007
6. Development of radiation sensors based on stacked RADFET technology , European Commission, Brussels, Belgium, 2013.
   Retrieved from: https://cordis.europa.eu/project/id/302031/reporting/en?format=pdf
   Retrieved on: Dec. 22, 2019
7. M. Scarafagio et al., "Ultra-Thin Eu and Er Doped Y 2 O 3 Films with Optimized Optical Properties for Quantum Technologies," J. Phys. Chem. C, vol. 123, no. 21, pp. 13354 – 13364, May 2019.
   DOI: 10.1021/acs.jpcc.9b02597
8. Y. Zhu, Z. Fang, Y. Liu, "Structural and optical properties of Er2O3 films," J. Rare Earths, vol. 28, no. 5, pp. 752 – 755, Oct. 2010.
   DOI: 10.1016/S1002-0721(09)60194-0
9. V. H. Mudavakkat, V. V. Atuchin, V. N. Kruchinin, A. Kayani, C. V. Ramana, "Structure, morphology and optical properties of nanocrystalline yttrium oxide (Y2O3) thin films," Opt. Mater., vol. 34, no. 5, pp. 893 – 900, Mar. 2012.
   DOI: 10.1016/j.optmat.2011.11.027
10. A. Cantas, G. Aygun, R. Turan, "Impact of incorporated oxygen quantity on optical, structural and dielectric properties of reactive magnetron sputter grown high-κ HfO2/Hf/Si thin film," Appl. Surf. Sci., vol. 318, pp. 199 – 205, Nov. 2014.
    DOI: 10.1016/j.apsusc.2014.03.077
11. M. Mishra et al., "Microstructure and optical properties of Gd2O3 thin films prepared by pulsed laser deposition," Surf. Coat. Technol., vol. 262, pp. 56 – 63, Jan. 2015.
    DOI: 10.1016/j.surfcoat.2014.12.012
12. S. Abubakar, E. Yilmaz, "Optical and electrical properties of E-Beam deposited TiO2/Si thin films," J. Mater. Sci. Mater. Electron., vol. 29, no. 12, pp. 9879 – 9885, Jun. 2018.
    DOI: 10.1007/s10854-018-9029-9
13. A. Kahraman, S. C. Deevi, E. Yilmaz, "Influence of frequency and gamma irradiation on the electrical characteristics of Er2O3, Gd2O3, Yb2O3, and HfO2 MOS-based devices," J. Mater. Sci., vol. 55, no. 81, pp. 7999 – 8040, Jul. 2020.
    DOI: 10.1007/s10853-020-04531-8
14. S. Kaya, R. Lok, A. Aktag, J. Seidel, E. Yilmaz, "Frequency dependent electrical characteristics of BiFeO3 MOS capacitors," J. Alloys Compd., vol. 583, pp. 476 – 480, Jan. 2014.
    DOI: 10.1016/j.jallcom.2013.08.204
15. A. Tataroǧlu, G. G. Güven, S. Yilmaz, A. Büyükbas, “Analysis of barrier height and carrier concentration of MOS capacitor using C-f and G/ω-f measurements,” Bull. Gazi University, vol. 27, no. 3, Ankara, Turkey, 2014.
    Retrieved from: https://dergipark.org.tr/en/download/article-file/83667
    Retrieved on: Jan. 10, 2020
16. S. Kaya, E. Yilmaz, "A comprehensive study on the frequency-dependent electrical characteristics of Sm2O3 MOS capacitors," IEEE Trans. Electron Devices, vol. 62, no. 3, pp. 980 – 987, Mar. 2015.
    DOI: 10.1109/TED.2015.2389953
17. H. Xiao, S. Huang, "Frequency and voltage dependency of interface states and series resistance in Al/SiO2/p-Si MOS structure," Mater. Sci. Semicond. Process., vol. 13, no. 5 – 6, pp. 395 – 399, Dec. 2010.
    DOI: 10.1016/j.mssp.2011.05.009
18. R. Oka et al., "High interfacial quality metal-oxide-semiconductor capacitor on (111) oriented 3C-SiC with Al2O3 interlayer and its internal charge analysis," Jpn. J. Appl. Phys., vol. 59, no. SG, article no. SGGD17, Apr. 2020.
    DOI: 10.35848/1347-4065/ab6862
19. R. Ahlawat, P. Aghamkar, "Influence of annealing temperature on Y2O3:SiO2 nanocomposite prepared by sol-gel process," Acta Phys. Pol. A, vol. 126, no. 3, pp. 736 – 739, Sep. 2014.
    DOI: 10.12693/APhysPolA.126.736