Modeling the Impact of Incomplete Dopant Ionization on Built in Potential and C–V Characteristics of GaN p–n Junctions: A SCAPS-1D Study
Abstract
Incomplete dopant ionization in wide-bandgap semiconductors plays a critical role in determining carrier concentration, electrostatic properties, and overall device performance; however, its impact on GaN p–n junctions for optical photovoltaic converters (OPCs) remains insufficiently understood. In this work, SCAPS-1D simulations are employed to systematically investigate GaN p–n junctions incorporating three p-type acceptors (Mg, Zn, Be) and three n-type donors (Si, O, S) over doping concentrations of 10¹⁵–10¹⁸ cm⁻³ and temperatures ranging from 77 K to 400 K. The temperature dependence of the bandgap is described by the Varshni relation (R² = 0.9721), while dopant ionization is modeled as a function of both temperature and doping level to capture its effects on carrier distribution, the built-in potential, and capacitance–voltage (C–V) characteristics. The results reveal a pronounced reduction in junction capacitance at lower temperatures due to incomplete acceptor ionization. For a representative doping level of 5×10¹⁷ cm⁻³, the capacitance decreases from approximately 3.2 pF at 400 K to 1.5 pF at 77 K (≈53% reduction), primarily due to partial ionization of Mg acceptors, while donor species remain nearly fully ionized. These findings demonstrate that conventional models that neglect incomplete ionization significantly overestimate junction capacitance at low temperatures. Although the analysis is based on a one-dimensional framework, it provides physically consistent insight into the role of deep-level dopants and establishes a basis for future multidimensional TCAD investigations. This study highlights the necessity of incorporating incomplete-ionization effects into the design and optimization of high-efficiency, radiation-resilient GaN-based OPCs operating in extreme environments.
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T. Maeda, T. Narita, S. Yamada, T. Kachi, T. Kimoto, M. Horita, and J. Suda, “Impact ionization coefficients and critical electric field in GaN,” Journal of Applied Physics, 129(18), 185702 (2021). https://doi.org/10.1063/5.0050793
S.J. Pearton, R. Deist, F. Ren, L. Liu, A.Y. Polyakov, and J. Kim, “Review of radiation damage in GaN-based materials and devices,” Journal of Vacuum Science and Technology A, 31(5), 050801 (2013). https://doi.org/10.1116/1.4799504
N. Donato, and F. Udrea, “Static and dynamic effects of the incomplete ionization in superjunction devices,” IEEE Transactions on Electron Devices, 65(10), 4469–4475 (2018). https://doi.org/10.1109/TED.2018.2867058
S.J. Pearton, Y.-S. Hwang, and F. Ren, “Radiation effects in GaN-based high electron mobility transistors,” Journal of Materials, 67, 1601–1611 (2015). https://doi.org/10.1007/s11837-015-1401-2
A.T. Neal, S. Mou, R. Lopez, J.V. Li, D.B. Thomson, K.D. Chabak, and G.H. Jessen, “Incomplete ionization of a 110 meV unintentional donor in β-Ga₂O₃ and its effect on power devices,” Scientific Reports, 7, 13218 (2017). https://doi.org/10.1038/s41598-017-13341-8
J.Sh. Abdullayev, and I.B. Sapaev, “Factors influencing the ideality factor of semiconductor p-n and p-i-n junction structures at cryogenic temperatures,” East European Journal of Physics, (4), 329–333 (2024). https://doi.org/10.26565/2312-4334-2024-4-37
M. Phifer, S. Hossain, J. Osborne, Z. Xie, and M. Alam, “Demonstration of TCAD modeling for GaN devices,” in: SoutheastCon. 2025, (IEEE, 2025), pp. 1–6. https://doi.org/10.1109/SoutheastCon56624.2025.10971621
H. Shang, and Y. Jiang, “A physical model of a diamond vertical Schottky diode including incomplete ionization and thermal effects,” Journal of Physics D: Applied Physics, 58(15), 155104 (2025). https://doi.org/10.1088/1361-6463/adb9fb
C. Onwukaeme, and H.-Y. Ryu, “Design of GaN-based laser diode structures with nonuniform doping distribution in a p-AlGaN cladding layer for high-efficiency operation,” Crystals, 15(3), 259 (2025). https://doi.org/10.3390/cryst15030259
J. Wei, J. Hao, Q. Zhao, J. Fan, F. Zhang, and Z. Dong, “Comparative study of wide-bandgap materials for neutron detection: GaN and 4H-SiC,” Nuclear Technology, 211(12), 3080–3093 (2025). https://doi.org/10.1080/00295450.2025.2462444
J.F. Lozano, N. Seoane, J.M. Guedes, E. Comesaña, J.G. Fernandez, F.M. Almonacid, E.F. Fernández, and A. García-Loureiro, “Gallium nitride: A strong candidate to replace GaAs as base material for optical photovoltaic converters in space exploration,” Optics and Laser Technology, 192(Part A), 113447 (2025). https://doi.org/10.1016/j.optlastec.2025.113447
J.Sh. Abdullayev, “Influence of linear doping profiles on the electrophysical features of p-n junctions. East European Journal of Physics, (1), 245–249 (2025). https://doi.org/10.26565/2312-4334-2025-1-26
J.Sh. Abdullayev, and I.B. Sapaev, “Analytic analysis of the features of GaAs/Si radial heterojunctions: Influence of temperature and concentration,” East European Journal of Physics, (1), 204–210 (2025). https://doi.org/10.26565/2312-4334-2025-1-21
J.Sh. Abdullayev, I.B. Sapaev, N. Esanmuradova, S. Kadirov, and S. Kuliyev, “Mathematical analysis of the features of radial p-n junction: Influence of temperature and concentration,” East European Journal of Physics, (2), 220–225 (2025). https://doi.org/10.26565/2312-4334-2025-2-24
S. Chatterjee, and M. Mukherjee, “Electrical Characterization in Ultra-Wide Band Gap III-Nitride Heterostructure IMPATT/HEMATT Diodes: A Room-Temperature Sub-Millimeter Wave Power Source,” J. Electron. Mater. 52, 1552–1563 (2023). https://doi.org/10.1007/s11664-022-10090-2
J.Sh. Abdullayev, I.B. Sapaev, and S.R. Kadirov, The role of recombination types in efficiency limits of radial p-n junctions based on Si and GaAs. East European Journal of Physics, (2), 252–257 (2025). https://doi.org/10.26565/2312-4334-2025-2-30
J.Sh. Abdullayev, I.B. Sapaev, J.S. Abdullayev, D.A. Juraev, M.J. Jalalov, and E.E. Elsayed, “Mathematical Modeling of Incomplete Ionization in Radial p-Si/n-GaAs Heterojunctions: Temperature and Doping Effects. J. Electron. Mater. 54, 10484–10492 (2025). https://doi.org/10.1007/s11664-025-12391-8
J.Sh. Abdullayev, L. Abdullayeva, L. Agamalieva, and R. Ismailova, “Correlating Ni microstructure with Schottky barrier homogeneity in monolayer MoS₂ field-effect transistors,” Advanced Physical Research, 7(3), 350–357 (2025). https://doi.org/10.62476/apr.73350
P. Murugapandiyan, K. Sri Rama Krishna, A. Revathy, and A. Fletcher, “Enhancement Mode AlGaN/GaN MISHEMT on Ultra-Wide Band Gap β-Ga2O3 Substrate for RF and Power Electronics,” J. Electron. Mater. 53, 2973–2987 (2024). https://doi.org/10.1007/s11664-024-11005-z
J.S. Abdullayev, D.A. Qalandarova, M.S. Ibragimova, I.B. Sapaev, and J.I. Razzokov, “Experimental and Simulation-Based Investigation of p-Si/n-CdS Heterojunctions: From Cryogenic Freeze-Out to Room Temperature Operation,” J. Electron. Mater. 55, 2229–2239 (2026). https://doi.org/10.1007/s11664-025-12642-8
A. Kumar, G. Kumar, and C. Kumar, “Design and Performance Evaluation of a Ge₁₋ₓSnₓ/Ge Multiple Quantum Well Heterojunction Phototransistor for Long-Haul DWDM Optical Communication Systems,” J. Electron. Mater. (2026). https://doi.org/10.1007/s11664-025-12653-5
M.A.A. Rosle, and M.Z. Pakhuruddin, “Investigation of gallium nitride emitter thickness in GaN/Si heterojunction solar cell by SCAPS-1D,” NanoVol, 20(09), 2550026 (2025). https://doi.org/10.1142/S1793292025500262
M.K. Omar, M. Rashid, and M.Z. Pakhuruddin, “Investigation on indium concentration in two-terminal tandem indium gallium nitride solar cells by SCAPS-1D,” Physica Scripta, 99(11), 115531 (2024). https://doi.org/10.1088/1402-4896/ad8193
H. Abboudi, W. Belaid, R. En-nadir, I. Ez-zejjari, M. Zouini, A. Sali, and H. El Ghazi, “Optimization of InₓGa₁−ₓN P-I-N solar cells: Achieving 21% efficiency through SCAPS-1D modeling,” Crystals, 15(7), 633 (2025). https://doi.org/10.3390/cryst15070633
Z. Hu, K. Nomoto, B. Song, M. Zhu, M. Qi, M. Pan, X. Gao, et al., “Near unity ideality factor and Shockley-Read-Hall lifetime in GaN-on-GaN p-n diodes with avalanche breakdown featured,” Applied Physics Letters, 107(24), 243501 (2015). https://doi.org/10.1063/1.4937436
J.S. Abdullayev, M.S. Ibragimova, J.Sh. Abdullayev, and I.B. Sapaev, “Cryogenic material and electrophysical changes in Si and GaAs,” East European Journal of Physics, (1), 343–350 (2026). https://doi.org/10.26565/2312-4334-2026-1-40
Y.-C. Lai, Y.-N. Zhong, M.-Y. Tsai, and Y.-M. Hsin, “Gate capacitance and off-state characteristics of E-mode p-GaN gate AlGaN/GaN high-electron-mobility transistors after gate stress bias,” Journal of Electronic Materials, 50, 1162–1166 (2021). https://doi.org/10.1007/s11664-020-08949-1
N. Bano, I. Hussain, E.A. Al-Ghamdi, and M.S. Ahmad, “Quantitative analysis of electrically active defects in Au/AlGaN/GaN HEMTs structure using capacitance–frequency and DLTS measurements,” Journal of Physics Communications, 5(12), 125010 (2021). https://doi.org/10.1088/2399-6528/ac41aa
S. Lv, S. Wang, J. Yu, G. Tian, G. Wang, P. An, K. Song, et al., “Wafer scale gallium nitride integrated electrode toward robust high temperature energy storage,” Small, 20(27), 2310837 (2024). https://doi.org/10.1002/smll.202310837
W. Yang, J.-S. Yuan, B. Krishnan, A.J. Tzou, and W.-K. Yeh, “C-V measurement under different frequencies and pulse-mode voltage stress to reveal shallow and deep trap effects of GaN HEMTs,” in: 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA), (Atlanta, GA, USA, 2018). https://doi.org/10.1109/WIPDA.2018.8569206
J. Park, S.H. Lee, I.M. Kang, and Y.J. Yoon, “Fabrication of AlGaN/GaN HEMT using TMAH pre-treatment and analysis of electrical characteristics by proton irradiation,” Current Applied Physics, 75, 33–39 (2025). https://doi.org/10.1016/j.cap.2025.04.010
H. Sun, Q. Fan, X. Ni, Q. Luo, and X. Gu, “Low-pressure chemical vapor deposition SiNx process study and its impact on interface characteristics of AlGaN/GaN MISHEMTs,” Micromachines, 16(4), 442 (2025). https://doi.org/10.3390/mi16040442
D.A. Qalandarova, M.S. Ibragimova, J.S. Abdullayev, and I.B. Sapaev, “Mathematical modeling of electrostatic potential in radial and planar p–n junctions: A comparative study,” East European Journal of Physics, (1), 333–342 (2026). https://doi.org/10.26565/2312-4334-2026-1-39
J.S. Abdullayev, M.S. Ibragimova, J.Sh. Abdullayev, and I.B. Sapaev, “Thermal expansion characteristics of planar and radial Si/GaAs p–n heterojunctions,” East European Journal of Physics, (1), 388–395 (2026). https://doi.org/10.26565/2312-4334-2026-1-46
H. Teisseyre, P. Perlin, T. Suski, I. Grzegory, S. Porowski, J. Jun, A. Pietraszko, and T.D. Moustakas, “Temperature dependence of the energy gap in GaN bulk single crystals and epitaxial layer,” Journal of Applied Physics, 76(4), 2429–2434 (1994). https://doi.org/10.1063/1.357592
C. Prall, M. Ruebesam, C. Weber, M. Reufer, and D. Rueter, “Photoluminescence from GaN layers at high temperatures as a candidate for in situ monitoring in MOVPE,” Journal of Crystal Growth, 397, 24–28 (2014). https://doi.org/10.1016/j.jcrysgro.2014.04.001
J.Sh. Abdullayev, D.A. Qalandarova, and M.Sh. Ibragimova, “Impact of incomplete ionization on the critical electric field of p n junction structures based on Si and GaAs,” Low Temperature Physics, 52(2), 164–169 (2026). https://doi.org/10.1063/10.0042291
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