AlGaN/GaN-based SBDs grown on silicon substrates with trenched n<sup>+</sup>-GaN cap layer and local passivation layer to improve BFOM and dynamic properties

Zhizhong Wang; Jingting He; Fuping Huang; Xuchen Gao; Kangkai Tian; Chunshuang Chu; Yonghui Zhang; Shuting Cai; Xiaojuan Sun; Dabing Li; Xiao Wei Sun; Zi-Hui Zhang

doi:10.1088/1674-4926/25010024

J. Semicond. > Just Accepted

ARTICLES

AlGaN/GaN-based SBDs grown on silicon substrates with trenched n⁺-GaN cap layer and local passivation layer to improve BFOM and dynamic properties

Zhizhong Wang¹, Jingting He², Fuping Huang², Xuchen Gao¹, Kangkai Tian², Chunshuang Chu², Yonghui Zhang¹, Shuting Cai², Xiaojuan Sun³, Dabing Li³, Xiao Wei Sun⁴ and Zi-Hui Zhang^{1, 2,}

+ Author Affiliations

1. State Key Laboratory of Reliability and Intelligence of Electrical Equipment and School of Electronics and Information Engineering, Hebei University of Technology, Tianjin 300401, China
2. School of Integrated Circuits, Guangdong University of Technology, Guangzhou 510006, China
3. State Key Laboratory of Luminescence and Applications Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences, Changchun 130033, China
4. Institute of Nanoscience and Applications, and Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China

Author Bio:

Zhizhong Wang got his bachelor’ degree in 2012 from Shanxi Datong University and his master’s degree in 2019 from Shenyang University of Technology. He is currently a Ph.D. candidate at Hebei University of Technology under the supervision of Prof. Zi-Hui Zhang. His research primarily focuses on the fabrication and analysis of gallium nitride power semiconductor devices.

Zi-Hui Zhang received his Ph.D. from Nanyang Technological University. He is a professor at the State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology and Guangdong University of Technology. He is also a “100-Talent-Plan” Distinguished Professor of Hebei Province. His research interests include III-nitride-based semiconductor materials and devices.

Corresponding author: Zi-Hui Zhang, zh.zhang@hebut.edu.cn

DOI: 10.1088/1674-4926/25010024CSTR: 32376.14.1674-4926.25010024

Abstract: In this work, we design and fabricate AlGaN/GaN-based Schottky barrier diodes (SBDs) on a silicon substrate with a trenched n⁺-GaN cap layer. With the developed physical models, we find that the n⁺-GaN cap layer provides more electrons into the AlGaN/GaN channel, which is further confirmed experimentally. When compared with the reference device, this increases the two-dimensional electron gas (2DEG) density by two times and leads to a reduced specific ON-resistance （R_on,sp）of ~2.4 mΩ·cm². We also adopt the trenched n⁺-GaN structure such that partial of the n⁺-GaN is removed by using dry etching process to eliminate the surface electrical conduction when the device is set in the off-state. To suppress the surface defects that are caused by the dry etching process, we also deposit Si₃N₄ layer prior to the deposition of field plate (FP), and we obtain a reduced leakage current of ~8 × 10⁻⁵ A·cm⁻² and breakdown voltage (BV) of 876 V. The Baliga’s figure of merit (BFOM) for the proposed structure is increased to ~319 MW·cm⁻². Our investigations also find that the pre-deposited Si₃N₄ layer helps suppress the electron capture and transport processes, which enables the reduced dynamic R_on,sp.

Key words: AlGaN/GaN-based Schottky barrier diodes (SBDs), n⁺-GaN cap layer, Si₃N₄ protective layer

References

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Fig. 1. (Color online) (a) Schematic energy band diagram for the AlGaN/GaN SBD with an n⁺-GaN cap layer. Schematic cross-section for lateral AlGaN/GaN SBDs: (b) without n⁺-GaN cap layer, (c) with n⁺-GaN cap layer, (d) with partial n⁺-GaN cap layer, (e) with partial n⁺-GaN cap layer and Si₃N₄ protective layer.

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Fig. 2. (Color online) (a) Forward current-voltage (J−V) characteristics and R_on,sp, and (b) reverse blocking effect for Devices A, B and C. Insets (b1) and (b2) show leakage paths J1 and J2 for Devices B and C, respectively. (c) C−V profiles in terms of the applied voltage, and (d) electron concentration profiles for AlGaN/GaN heterostructures with/without n⁺-GaN layer.

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Fig. 3. (Color online) Cross-sectional high-resolution transmission electron microscope micrographs for the lateral AlGaN/GaN SBDs with partial n⁺-GaN cap layer: (a) without Si₃N₄ protective layer, (b) with Si₃N₄ protective layer. (c) Experimental forward J−V characteristics and R_on,sp for Devices C and D. (d) J−V characteristics in semi-log scale for Devices C and D.

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Fig. 4. (Color online) (a) Temperature-dependent reverse J−V characteristics of Device C from 300 to 380 K. (b) Linear relationship between Ln (J) and (1/T)^1/3 for Device C. Inset figure shows leakage current models for Device C. (c) Reverse J−V characteristics for Devices C, C1, C2, C3, C3−1, C3−2, and C3−3. (d) Reverse J−V characteristics for Devices C, C4 and C5.

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Fig. 5. (Color online) (a) Experimental and simulated reverse J−V characteristics for Devices C and D. Leakage current distribution profiles for Devices C and D: (b1) 2-D, (b2) 1-D. (c) Temperature-dependent reverse J−V characteristics of the Device D from 300 to 400 K. (d) Linear relationship between Ln (J) and Ln (T²) for Device D.

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Fig. 6. (Color online) Benchmark of (a) R_on,sp in terms of BV and (b) V_on in terms of reverse current at the reverse voltage of −100 V for the fabricated Devices C and D in this work and other reported SBDs.

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Fig. 7. (Color online) (a) − (f) Electrical stress characteristics for Devices C and D with varying stress voltages of −50, −100 and −150 V, respectively. (g) R_{on,sp_stress}/R_on,sp in terms of stress time for Devices C and D at different stress voltages.

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Table 1. Trap information for GaN layers grown on different substrates.

Trap level (eV)	Trap density (cm⁻³)	Capture cross-section (cm²)	Substrate	Reference
E_c−0.23	9.5 × 10¹³	5.43 × 10⁻¹⁵	Sapphire	[34]
E_c−0.60	3.2 × 10¹⁴	1.61 × 10⁻¹⁵	Sapphire	[34]
E_c−0.17	3.5 × 10¹⁴	8.7 × 10⁻¹⁸	Sapphire	[35]
E_c−0.24	5.5 × 10¹⁴	2.6 × 10⁻¹⁸	Sapphire	[35]
E_c−0.59	8.5 × 10¹³	9.0 × 10⁻¹⁶	Sapphire	[35]
E_c−0.57	~ 10¹⁶	3.0 × 10⁻¹⁵	Silicon	[36]
E_c−0.70	5.5 × 10¹⁴	3.0 × 10⁻¹⁵	Silicon	[33]

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Table 2. Structural information for different AlGaN/GaN SBDs.

Device No.	Bulk trap density (cm⁻³)	Interface trap density (cm⁻²)	Impact ionization models	Experiment /Simulation	Substrate
Device A	−	−	−	Experiment	Silicon
Device B
Device C
Device C1	1.0 × 10^13[40]	−	(1), (2)	Simulation	Sapphire
Device C2	1.0 × 10^14[40]
Device C3	1.0 × 10^15[40]
Device C3−1	1.0 × 10¹⁵	1.0 × 10^12[41]
Device C3−2		1.0 × 10^14[42]
Device C3−3		1.0 × 10^16[43]
Device C4	1.0 × 10¹⁵	-	(3), (4)	Simulation	Silicon
Device C5	1.0 × 10¹⁵	1.0 × 10^13[10]	(3), (4)	Simulation
Device D	−	−	−	Experiment
Device D1	1.0 × 10¹⁵	1.0 × 10¹³	(3), (4)	Simulation
Device D2	1.0 × 10¹⁵	−	(3), (4)	Simulation

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[1]	Islam N, Mohamed M F P, Khan M F A J, et al. Reliability, applications and challenges of GaN HEMT technology for modern power devices: A review. Crystals, 2022, 12(11), 1581 doi: 10.3390/cryst12111581
[2]	Mounika B, Ajayan J, Bhattacharya S, et al. Recent developments in materials, architectures and processing of AlGaN/GaN HEMTs for future RF and power electronic applications: A critical review. Micro Nanostruct, 2022, 168, 207317 doi: 10.1016/j.micrna.2022.207317
[3]	Zhang T, Wang Y, Zhang Y N, et al. Comprehensive annealing effects on AlGaN/GaN Schottky barrier diodes with different work-function metals. IEEE Trans Electron Devices, 2021, 68(6), 2661 doi: 10.1109/TED.2021.3074896
[4]	Zhou Q, Jin Y, Shi Y Y, et al. High reverse blocking and low onset voltage AlGaN/GaN-on-Si lateral power diode with MIS-gated hybrid anode. IEEE Electron Device Lett, 2015, 36(7), 660 doi: 10.1109/LED.2015.2432171
[5]	Rajagopal Reddy V, Janardhanam V, Ju J W, et al. Electronic parameters and carrier transport mechanism of high-barrier Se Schottky contacts to n-type GaN. Solid State Commun, 2014, 179, 34 doi: 10.1016/j.ssc.2013.11.011
[6]	Yang X X, Cheng Z, Yu Z G, et al. The influence of anode trench geometries on electrical properties of AlGaN/GaN Schottky barrier diodes. Electronics, 2020, 9(2), 282 doi: 10.3390/electronics9020282
[7]	Wang T F, Zong Y, Nela L, et al. Enhancement-mode multi-channel AlGaN/GaN transistors with LiNiO junction tri-gate. IEEE Electron Device Lett, 2022, 43(9), 1523 doi: 10.1109/LED.2022.3189635
[8]	Nela L, Xiao M, Zhang Y H, et al. A perspective on multi-channel technology for the next-generation of GaN power devices. Appl Phys Lett, 2022, 120(19), 190501 doi: 10.1063/5.0086978
[9]	Li C K, Wu Y R. Study on the current spreading effect and light extraction enhancement of vertical GaN/InGaN LEDs. IEEE Trans Electron Devices, 2012, 59(2), 400 doi: 10.1109/TED.2011.2176132
[10]	Ibbetson J P, Fini P T, Ness K D, et al. Polarization effects, surface states, and the source of electrons in AlGaN/GaN heterostructure field effect transistors. Appl Phys Lett, 2000, 77(2), 250 doi: 10.1063/1.126940
[11]	Lee J H, Im K S, Lee J H. Effect of In-situ silicon carbon nitride (SiCN) cap layer on performances of AlGaN/GaN MISHFETs. IEEE J Electron Devices Soc, 2021, 9, 728 doi: 10.1109/JEDS.2021.3100760
[12]	Hsu L, Jones R E, Li S X, et al. Electron mobility in InN and III-N alloys. J Appl Phys, 2007, 102(7), 073705 doi: 10.1063/1.2785005
[13]	Wang J X, Yang S Y, Wang J, et al. Electron mobility limited by surface and interface roughness scattering in Al_xGa_{1− x}N/GaN quantum wells. Chin Phys B, 2013, 22(7), 077305 doi: 10.1088/1674-1056/22/7/077305
[14]	Ko T S, Lin D Y, Lin C F, et al. High-temperature carrier density and mobility enhancements in AlGaN/GaN HEMT using AlN spacer layer. J Cryst Growth, 2017, 464, 175 doi: 10.1016/j.jcrysgro.2016.12.023
[15]	Liu Z H, Ng G I, Zhou H, et al. Reduced surface leakage current and trapping effects in AlGaN/GaN high electron mobility transistors on silicon with SiN/Al₂O₃ passivation. Appl Phys Lett, 2011, 98(11), 113506 doi: 10.1063/1.3567927
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Received: 19 January 2025 Revised: 17 March 2025 Online: Accepted Manuscript: 10 April 2025

Article Navigation > Journal of Semiconductors > 2025 > Accepted Manuscript

Zhizhong Wang, Jingting He, Fuping Huang, Xuchen Gao, Kangkai Tian, Chunshuang Chu, Yonghui Zhang, Shuting Cai, Xiaojuan Sun, Dabing Li, Xiao Wei Sun, Zi-Hui Zhang. AlGaN/GaN-based SBDs grown on silicon substrates with trenched n+-GaN cap layer and local passivation layer to improve BFOM and dynamic properties[J]. Journal of Semiconductors, 2025, In Press. doi: 10.1088/1674-4926/25010024 ****Z Z Wang, J T He, F P Huang, X C Gao, K K Tian, C S Chu, Y H Zhang, S T Cai, X J Sun, D B Li, X W Sun, and Z-H Zhang, AlGaN/GaN-based SBDs grown on silicon substrates with trenched n+-GaN cap layer and local passivation layer to improve BFOM and dynamic properties[J]. J. Semicond., 2025, accepted doi: 10.1088/1674-4926/25010024

Citation:

Z Z Wang, J T He, F P Huang, X C Gao, K K Tian, C S Chu, Y H Zhang, S T Cai, X J Sun, D B Li, X W Sun, and Z-H Zhang, AlGaN/GaN-based SBDs grown on silicon substrates with trenched n⁺-GaN cap layer and local passivation layer to improve BFOM and dynamic properties[J]. J. Semicond., 2025, accepted doi: 10.1088/1674-4926/25010024

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AlGaN/GaN-based SBDs grown on silicon substrates with trenched n⁺-GaN cap layer and local passivation layer to improve BFOM and dynamic properties

DOI: 10.1088/1674-4926/25010024

CSTR: 32376.14.1674-4926.25010024

1.
State Key Laboratory of Reliability and Intelligence of Electrical Equipment and School of Electronics and Information Engineering, Hebei University of Technology, Tianjin 300401, China
2.
School of Integrated Circuits, Guangdong University of Technology, Guangzhou 510006, China
3.
State Key Laboratory of Luminescence and Applications Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences, Changchun 130033, China
4.
Institute of Nanoscience and Applications, and Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China

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Zhizhong Wang got his bachelor’ degree in 2012 from Shanxi Datong University and his master’s degree in 2019 from Shenyang University of Technology. He is currently a Ph.D. candidate at Hebei University of Technology under the supervision of Prof. Zi-Hui Zhang. His research primarily focuses on the fabrication and analysis of gallium nitride power semiconductor devices
Zi-Hui Zhang received his Ph.D. from Nanyang Technological University. He is a professor at the State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology and Guangdong University of Technology. He is also a “100-Talent-Plan” Distinguished Professor of Hebei Province. His research interests include III-nitride-based semiconductor materials and devices
Corresponding author: zh.zhang@hebut.edu.cn
Received Date: 2025-01-19
Revised Date: 2025-03-17

Available Online: 2025-04-10

Abstract

Abstract

In this work, we design and fabricate AlGaN/GaN-based Schottky barrier diodes (SBDs) on a silicon substrate with a trenched n⁺-GaN cap layer. With the developed physical models, we find that the n⁺-GaN cap layer provides more electrons into the AlGaN/GaN channel, which is further confirmed experimentally. When compared with the reference device, this increases the two-dimensional electron gas (2DEG) density by two times and leads to a reduced specific ON-resistance （R_on,sp）of ~2.4 mΩ·cm². We also adopt the trenched n⁺-GaN structure such that partial of the n⁺-GaN is removed by using dry etching process to eliminate the surface electrical conduction when the device is set in the off-state. To suppress the surface defects that are caused by the dry etching process, we also deposit Si₃N₄ layer prior to the deposition of field plate (FP), and we obtain a reduced leakage current of ~8 × 10⁻⁵ A·cm⁻² and breakdown voltage (BV) of 876 V. The Baliga’s figure of merit (BFOM) for the proposed structure is increased to ~319 MW·cm⁻². Our investigations also find that the pre-deposited Si₃N₄ layer helps suppress the electron capture and transport processes, which enables the reduced dynamic R_on,sp.
- AlGaN/GaN-based Schottky barrier diodes (SBDs),
- n⁺-GaN cap layer,
- Si₃N₄ protective layer

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