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Qihao Zhang, [Jiangwei Liu](https://orcid.org/0000-0003-2580-7401), Chunming Tu, Dongyuan Zhai, Min He, Jiwu Lu

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[High-performance β-Ga2O3 Schottky barrier diodes and metal-semiconductor field-effect transistors on a high doping level epitaxial layer](https://mdr.nims.go.jp/datasets/85fbef0c-37e6-4125-9b79-c695f3a1c566)

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1   High-Performance β-Ga2O3 Schottky barrier diodes and Metal-Semiconductor Field-Effect Transistors on a Non-Delta-Doped High Doping Level Epitaxial layer  Qihao Zhanga, Jiangwei Liub, Chunming Tua, Dongyuan Zhaia, *, Min Hea, Jiwu Lua, *  a College of Electrical and Information Engineering, Hunan University, Changsha, Hunan 410082, People’s Republic of China b Research Center for Functional Materials, National Institute for Materials Science, Ibaraki 305-0044, Japan Email: jiwu_lu@hnu.edu.cn and dyzhai@hnu.edu.cn  Abstract High-performance β-Ga2O3-based Schottky barrier diodes (SBDs) and metal-semiconductor field-effect transistors (MESFETs) are fabricated on a non-delta-doped high doping level (>1018 cm-3) epitaxial wafer. Their electrical properties and stabilities after annealing at 200~400 °C are investigated. The ON/OFF ratios for all the SBDs are over 108. The ideality factors and Schottky barrier heights for the Au/β-Ga2O3 SBDs with different annealing temperatures range from 1.5 to 2.5 and from 0.8 eV to 1.0 eV, respectively. There are obvious pinch-off and saturation characteristics for the β-Ga2O3 MESFETs. The maximum drain current (ID,max) for the as-fabricated β-Ga2O3 MESFET is 46.8 mA/mm at anode voltage of 2.0 V. They are much higher than the previously reported values of non-delta-doped and nanobelt β-Ga2O3 MESFETs. Threshold voltages for the β-Ga2O3 MESFETs shift to the negative direction with the increase of annealing temperature. This study is meaningful to push forward the development of β-Ga2O3-based electronic devices for practical applications. Keywords: β-Ga2O3, Schottky barrier diode, MESFET, high doping level  1.  Introduction With the development of power electrical techniques, conventional silicon-based power devices have reached theoretical limitations due to the intrinsic properties of silicon [1]. Third-generation semiconductors such as SiC- and GaN-based power devices have made great progress because of their advantages including wide bandgap energies, high carrier mobilities, high electron saturation velocities, and large thermal conductivities [2, 3]. Their remarkable intrinsic properties promise excellent performances in high breakdown voltage, low power-loss, high-frequency, and high-temperature applications. Recently, β-Ga2O3 has attracted lots of attention in next-generation electronic devices. Compared with the SiC and GaN, the β-Ga2O3 has a larger bandgap energy of ~4.9 eV, a higher theoretical breakdown electric field of ~8.0 MV/cm, and a higher Baliga’s figure of merit of 3214 [4]. Additionally, a large-area, low-cost, and high-quality β-Ga2O3 single-crystalline wafer has been commercially available [5], which provides powerful supports to fabricate Ga2O3-based electronic devices for practical applications such as in space exploration, high-speed rail, and renewable energy power system.  In recent years, the Ga2O3-based metal-semiconductor field-effect transistors (MESFETs) [6–11] have been developed greatly. Higashiwaki et al. [6] firstly reported Sn-doped β-Ga2O3-based MESFETs on a Ga2O3 epitaxial layer grown by a molecular beam epitaxy (MBE) technique. Although they showed good operations, the maximum output current (ID,max) was not very high (23.9 mA/mm), which possibly resulted from the low doping concentration (7.0 × 1017 cm-3) for the β-Ga2O3. Dang et al. [7] deposited an α-Ga2O3 film on sapphire via a mist-chemical vapor deposition technique for fabricating the MESFETs with a PtOx Schottky gate. Unfortunately, the quality of α-Ga2O3 epitaxial layer was  poor, which led to the low channel mobility (1.3 cm2/Vs) and the low ID,max (0.13 mA/mm) for the MESFET. Bae et al. [8] and Ma et al. [9] exfoliated mechanically the quasi-two-dimensional β-Ga2O3 flakes and transferred them on SiO2/Si substrates to fabricate the MESFETs, respectively. However, the fabrication processes were complicated and the ID,max value   2   (~5.6 mA/mm) was still not satisfactory. Rajan’s Group [10−12] made great efforts to grow delta-doped β-Ga2O3 epitaxial layers for fabricating the MESFETs. The delta-doping β-Ga2O3 was completed in a thin epitaxial layer (~0.2 nm) with an extremely high doping level (~1021 cm-3) [12]. There were excellent electrical properties for the delta-doped β-Ga2O3-based MESFETs such as a high channel mobilities (95 cm2/Vs) and a large ID,max value (180 mA/mm) [10, 11]. However, since it needs a high operation technique for the growth of delta-doped β-Ga2O3 epitaxial layer, it is a big challenge to promote this technique for wide applications.  In this study, we attempt to fabricate the Schottky barrier diodes (SBDs) and MESFETs on non-delta-doped high doping level (>1018 cm-3) β-Ga2O3 epitaxial wafer. Their electrical properties will be investigated and compared with the previous reports. The annealing effect on the β-Ga2O3-based SBDs and MESFETs will be discussed. 2.  Experimental The β-Ga2O3 epitaxial wafer with dimension of 10 mm × 15 mm × 0.5 mm was purchased from Japan Novel Crystal Technology, Inc. A 200 nm-thick Si-doped (010) epitaxial layer was grown on the Fe-doped semi-insulating substrate with a 200 nm-thick unintentionally doped (UID) buffer layer by the MBE technique. The effective donor concentration of the channel layer was extracted to be around 2.0 × 1018 cm-3 via an electrochemical capacitance-voltage profiling method.  The β-Ga2O3 epitaxial wafer was cleaned in acetone, alcohol, and SPM solvent (H2SO4 and H2O2 mixed solution) for 3, 3, and 5 min, respectively, followed by dipping in deionized water for 15 min. For preparing graphical ohmic contact electrodes, a positive photoresist (AR-P5350) was spin-coated on the sample with a rotation rate of 4000 rpm/min for 1 min. The cathode patterns were formed after the standard lithography process. The Ti/Au (20/80 nm) bilayer were formed by a magnetron sputtering deposition system at the chamber pressure of 5.0 × 10-6 Torr [Figs. 1(a, b-ii)]. The deposition rates for Ti and Au were 6.25 nm/min and 100 nm/min, respectively. The sample was thermally annealed at 500 °C for 10 min to form Ohmic contact for the Au/Ti/β-Ga2O3. The anode and gate electrode of Au for both SBD and MESFET were formed by the magnetron sputtering method with the thickness and sputtering rate of 100 nm and 60 nm/min, respectively. In order to investigate thermal stabilities of them, the sample was annealed at 200, 300, and 400 °C in a tube-heated furnace under a N2 gas atmosphere with an annealing time for each temperature of 10 min. Their electrical properties were measured with a B1500 parameter analyzer and a four-prober system at room temperature. 3.  Results and discussion 3.1. Structure of SBD and MESFET Figures 1(a) and 1(b) show the optical images of the β-Ga2O3 SBD and MESFET, respectively. Their cross-sectional views are shown in Figs. 1(c) and 1(d), respectively. The radius and area of the anode for the β-Ga2O3 SBD are 50 μm and 7.85 × 10-5 cm-2, respectively. The gap spacing between anode and cathode is 10 μm. For the β-Ga2O3 MESFET, the gate length (LG), gap spacing between source and gate electrodes, and gap spacing between gate and drain electrodes are 5, 10, and 10 μm, respectively. As the radius of the drain electrode for the β-Ga2O3 MESFET is 50 μm, the gate width (WG) can be computed to be 0.314 mm. 3.2. Electrical Properties of the Au/β-Ga2O3 SBD Figure 2 shows the current density (J)–voltage (V) characteristic for the β-Ga2O3 SBDs. The voltage varies from -5.0 to 10.0 V. Inset figure shows the enlarged curves with the voltage ranging from 9.0 V to 10.0 V. For the as-fabricated SBD, the maximum J (Jmax) is 905.2 A/cm2 at the anode voltage of 10.0 V. After the sample is annealed at 200 and 300 °C, the Jmax values increase gradually to 950.2 and 970.3 A/cm2, respectively. However, as the annealing temperature enhances to 400 °C, the Jmax decreases to 717.1 A/cm2. When the voltage is lower than zero, the J values for the as-fabricated, 300 °C-annealed, and 400 °C-annealed β-Ga2O3 SBDs are less than 10−5 A/cm2. Their ON/OFF ratios are in a 108 level. That for the 200 °C-annealed one is less than 10−8 A/cm2 with the ON/OFF ratio as large as 1.5 × 1011. Comparing with the as-fabricated Schottky diode, annealing at 200 °C possibly modifies the plasma damage for the β-Ga2O3 during the formation of Au electrode by the magnetron sputtering technique [13], which improves the OFF current and ON/OFF ratio for the SBD. As the annealing temperatures increase to 300 and 400 °C, the interfacial qualities of Au/β-Ga2O3 are possibly degraded at high-temperature. This is the possible   Figure 1. Optical images of the β-Ga2O3-based (a) SBD and (b) MESFET, respectively. (c) and (d) cross-sectional views of them, respectively. Si-doped β-Ga2O3UID β-Ga2O3Fe-doped semi-insulating β-Ga2O3 substrate10 μm10 μmSchottky Ohmic100 μmGate50 μm 50 μmDrainSourceAnodeCathodeOhmicSi-doped β-Ga2O3UID β-Ga2O3Fe-doped semi-insulating β-Ga2O3 substrate10 μm10 μmGate DrainSource5 μm(a) (b)(c) (d)  3   reason for the lower ON/OFF ratios at higher annealing temperatures. The measured J–V characteristics for the Au/β-Ga2O3 SBDs follow the thermionic emission (TE) model under V > 3kBT/q condition [14]: 𝐽 = 𝐽𝑆[exp⁡(𝑞𝑉𝑛𝑘𝐵𝑇) − 1],                      (1) where the q, n, kB, and T are the elementary charge (1.6 × 10-19 C), ideality factor, Boltzmann constant (1.38 × 10-23 J/K), and room temperature (300 K), respectively. The JS is saturation current density, given by: 𝐽𝑆 = 𝐴∗𝑇2exp⁡(−𝑞Φ𝐵𝑘𝐵𝑇),                       (2) where the A* is the effective Richardson constant for β-Ga2O3 (41 A/cm2∙K2) [15]. The ΦB is the Schottky height of Au/β-Ga2O3 interface. By fitting the data in Fig. 3, the JS, n, and ΦB can be deduced based on Eq. (1) and Eq. (2), which are summarized in Table I. The n and ΦB range from 1.5 to 2.5 and from 0.8 eV to 1.0 eV, respectively. The high n values for the Au/β-Ga2O3 SBDs are possibly ascribed to the spatial inhomogeneity between Au and β-Ga2O3 epitaxial layer. The same phenomena were also observed in other previous reports [16–19]. Additionally, when the Au metals were deposited on other semiconductors such as GaN [20], GaAs   [21], and diamond [22], the same situation happened. In the following study, the change of anode and the improvement of the Au/β-Ga2O3 interfacial quality would be performed to resolve this issue.  3.3. Electrical Properties of the Au/β-Ga2O3 MESFETs Figures 3(a)–3(d) show drain current versus drain voltage (ID−VD) characteristics for the as-fabricated, 200 °C-, 300 °C-, and 400 °C-annealed β-Ga2O3 MESFETs, respectively. For the former three MESFETs, gate-to-source voltage (VGS) varies from –15.0 to 2.0 V. That for the 400 °C-annealed one changes from −10.0 to 2.0 V. There are obvious pinch-off and saturation characteristics for the ID–VD curves of the as-fabricated, 200 °C-annealed, and 300 °C-annealed β-Ga2O3 MESFETs. The 400 °C-annealed one still operates well at VGS = –3.0 ~ 2.0 V. However, when the VGS varies from −10.0 to –4.0 V, its ID values increase sharply with the change of VD. One possible explanation is that the Au/β-Ga2O3 interface suffers great damage after annealing at 400 °C. The ID,max for the as-fabricated β-Ga2O3 MESFET is 46.8 mA/mm at VGS = 2.0 V. Annealing at 200, 300, and 400 °C make it increase to 54.3, 59.5, and 70.5 mA/mm, respectively. The on-resistance (RON) normalized by the WG for the β-Ga2O3 MESFETs can be obtained by fitting the linear regions of the ID–VD characteristics. They are extracted to be 155.7, 148.5, 139.4, and 134.0 Ω mm for the as-fabricated, 200 °C-, 300 °C-, and 400 °C-annealed MESFETs, respectively. Annealing makes the ID,max increase and the RON decrease for the β-Ga2O3 MESFETs. These are possibly caused by the following two factors. On one hand, the RON of the MESFET is composed of Ohmic contact resistance, surface resistance, and channel resistance, annealing possibly improves the channel resistance under gate region. On the other hand, the modification of ΦB for the Au/β- Ga2O3 interface may affect the ID,max and RON of the β-Ga2O3 MESFETs.  The √𝐼𝐷  as the function of VGS for the as-fabricated and annealed β-Ga2O3 MESFETs is shown in Fig. 4(a). By fitting the linear regions of the curves, threshold voltage (VTH) values for them are determined to be −9.5, −11.3, −14.3, and −15.0 V, respectively, which are summarized in Fig. 4 (b). All the β-Ga2O3 MESFETs operate in normally-on modes. With the   Figure 2. The J−V characteristics for the β-Ga2O3 SBDs. Inset figure shows the enlarged curves at the voltage ranging from 9.0 V to 10.0 V.  Table Ⅰ Electrical properties of the β-Ga2O3 SBDs   Jmax (A/cm2) ON/OFF Js  (A/cm2) n ФB (eV) As-fabricated 905.2 3.1 × 108 9.2 × 10−9 1.6 0.9 200 ºC-annealed 950.2 1.5 ×1011 1.5 ×10−10 1.7 1.0 300 ºC-annealed 970.3 7.2 × 108 6.5 × 10−12 1.5 1.0 400 ºC-annealed 717.1 1.4 × 108 1.4 × 10−7 2.5 0.8  -4 -2 0 2 4 6 8 101E-91E-71E-50.0010.1101000Voltage (V)J(A/cm2)As-fabricated200 °C-annealed300 °C-annealed400 °C-annealed9.0 9.2 9.4 9.6 9.8 10.06007008009001000  Figure 3. (a)–(d) The ID–VD characteristics for the non-annealed and annealed β-Ga2O3 MESFETs respectively. 0 2 4 6 8 10 120102030405060700 2 4 6 8 10 12010203040506070I D(mA/mm)I D(mA/mm)0 2 4 6 8 10 120102030405060700 2 4 6 8 10 12010203040506070VD (V)VGS: −15.0 ~ 2.0 VSteps: +1.0 VVD (V)VGS: −15.0 ~ 2.0 VSteps: +1.0 VVD (V)I D(mA/mm)VGS: −15.0 ~ 2.0 VSteps: +1.0 VVD (V)VGS: −10.0 ~ 2.0 VSteps: +1.0 VI D(mA/mm)As-fabricated 200 ºC-annealed300 ºC-annealed 400 ºC-annealed(a)(d)(b)(c)2.0 V-15.0 V2.0 V-15.0 V2.0 V-15.0 V2.0 V-10.0 V  4   increment of annealing temperature, the VTH shifts to the negative direction. The extrinsic transconductance (gm) as the function of VGS for the β-Ga2O3 MESFETs is summarized in Fig. 4(c). For the as-fabricated β-Ga2O3 MESFET, the maximum gm (gm,max) is extracted to be 7.7 mS/mm (2.4 mS). They are 7.5, 6.6, and 6.1 mS/mm after the sample annealing at 200, 300 and 400 °C, respectively. Fig. 4(d) summarizes annealing effects on the gm,max for the β-Ga2O3 MESFET. The gm,max decreases gradually with the increment of annealing temperature. 4.  Conclusion In summary, the β-Ga2O3 SBDs and MESFETs were assembled on the non-delta-doped high doping level epitaxial wafer. The effects of annealing temperature (200~400 °C) on their electrical properties were discussed. The Jmax and ON/OFF ratio of the as-fabricated SBD reached 905.2 A/cm2 and 108 level, respectively. As the annealing temperature increased to 200 °C, they were improved to be 950.2 A/cm2 and 1.5 × 1011, respectively. When the annealing temperature was enhanced to 400 °C, the Jmax and ON/OFF ratio degraded to 717.1 A/cm2 and 108 level, respectively. The n and ΦB for the SBDs ranged from 1.5 to 2.5 and from 0.8 eV to 1.0 eV, respectively. The ID,max values for the as-fabricated, 200 °C-, 300 °C-, and 400 °C-annealed β-Ga2O3 MESFETs were 46.8, 54.3, 59.5, and 70.5 mA/mm, respectively. They were larger than those of the previously reported non-delta-doped Ga2O3-based MESFETs. The absolute VTH values increased gradually with the increment of annealing temperature. The gm,max values for them were 7.7, 7.5, 6.6, and 6.1 mS/mm, respectively, which were also higher than those of the previous reports. The fabrication of high-performance β-Ga2O3 SBDs and MESFETs is meaningful to push forward the β-Ga2O3-based electronic devices for practical applications. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was supported in part by the National Key R&D Program of China under Grant 2018YFB1201802, in part by the National Natural Science Foundation of China under Grant 51977065, Grant 51807054, and Grant 52177179, and in part by the Science and Technology Innovation Program of Hunan Province, People’s Republic of China, under Grant 2019RS1024, and Grant 2020RC5004. References [1] B. J. Baliga, The future of power semiconductor device technology, Proc. IEEE. 89 (2001) 822–832. https://doi.org/10.1109/5.931471. [2] X. She, A. Q. Huang, O. Lucia, B. Ozpineci, Review of Silicon Carbide Power Devices and Their Applications, IEEE Trans. Ind. Electron. 64 (2017) 8193–8205. https://doi.org/10.1109/tie.2017.2652401. [3] E. A. Jones, F. F. Wang, D. Costinett, Review of Commercial GaN Power Devices and GaN-Based Converter Design Challenges, IEEE Trans. Emerg. Sel. Topics Power Electron. 4 (2016) 707–719. https://doi.org/10.1109/jestpe.2016.2582685. [4] S. J. Pearton, J. Yang, P. H. Cary, F. Ren, J. Kim, M. J. Tadjer, M. A. Mastro, A review of Ga2O3 materials, processing, and devices, Appl. Phys. Rev. 5 (2018) 011301. https://doi.org/10.1063/1.5006941. [5] A. Kuramata, K. Koshi, S. Watanabe, Y. Yamaoka, T. Masui, S. Yamakoshi, High-quality β-Ga2O3 single crystals grown by edge-defined film-fed growth, Jpn. J. Appl. Phys. 55 (2016) 1202A2. https://doi.org/10.7567/jjap.55.1202a2. [6] M. Higashiwaki, K. Sasaki, A. Kuramata, T. Masui, S. Yamakoshi, Gallium oxide (Ga2O3) metal-semiconductor field-effect transistors on single-crystal β-Ga2O3 (010) substrates, Appl. Phys. Lett. 100 (2012) 013504. https://doi.org/10.1063/1.3674287. [7] G. T. Dang, T. Kawaharamura, M. Furuta, M. W. Allen, Mist-CVD Grown Sn-Doped α-Ga2O3 MESFETs, IEEE Trans. Electron Devices. 62 (2015) 3640–3644. https://doi.org/10.1109/ted.2015.2477438. [8] J. Bae, H. W. Kim, I. H. Kang, G. Yang, J. Kim, High breakdown voltage quasi-two-dimensional β-Ga2O3 field-effect transistors with a boron nitride field plate, Appl. Phys. Lett. 112 (2018) 122102. https://doi.org/10.1063/1.5018238. [9] J. Ma, H. J. Cho, J. Heo, S. Kim, G. Yoo, Asymmetric Double‐Gate β‐Ga2O3 Nanomembrane Field‐Effect Transistor for Energy‐Efficient Power Devices, Adv. Electron. Mater. 5 (2019) 1800938. https://doi.org/10.1002/aelm.201800938. [10] Z. Xia, C. Joishi, S. Krishnamoorthy, S. Bajaj, Y. Zhang, M. Brenner, S. Lodha, S. Rajan, Delta Doped β-Ga2O3 Field Effect Transistors With   Figure 4. (a) √𝐼𝐷 –VGS and (c) gm–VGS for the β-Ga2O3 MESFETs, respectively, (c) VTH and (d) influence of annealing temperature on gm,max for the β-Ga2O3 MESFETs, respectively.  Table Ⅱ Comparison of our β-Ga2O3 MESFET with the previously reported MESFETs [6–9]   LG (μm) ID,max (mA/mm) VTH (V) gm,max (mS/mm) MESFET [6] 4 ~ 23.9 ~ −15 ~ 2.2 MESFET [7] 10 ~ 0.13 −0.8 0.5 MESFET [8] ~ 12 ~ 2 −7.3 ~ 0.2 MESFET [9] 4.2 ~ 5.6 −7.1 0.68 MESFET [This work] 5 46.8 −9.5 7.7  -14 -12 -10 -8 -6 -4 -2 0 2012345678gm(mS/mm)VGS (V)As-fabricated200 °C-annealed300 °C-annealed400 °C-annealed-14 -12 -10 -8 -6 -4 -2 0 2012345678RT 200 300 4006.06.46.87.27.68.0VGS (V)(mA0.5mm0.5)Annealing temperature (°C)RT 200 300 400-9-10-11-12-13-14-15-16Annealing temperature (°C)VTH(V)gm, max (mS/mm)As-fabricated200 °C-annealed300 °C-annealed400 °C-annealed(a)(d)(b)(c)  5   Regrown Ohmic Contacts, IEEE Electron Device Lett. 39 (2018) 568–571. https://doi.org/10.1109/led.2018.2805785. [11] C. Joishi, Z. Xia, J. S. Jamison, S. H. Sohel, R. C. Myers, S. Lodha, S. Rajan, Deep-Recessed β-Ga2O3 Delta-Doped Field-Effect Transistors With In Situ Epitaxial Passivation, IEEE Trans. Electron Devices. 67 (2020) 4813–4819. https://doi.org/10.1109/ted.2020.3023679. [12] S. Krishnamoorthy, Z. Xia, S. Bajaj, M. Brenner, S. Rajan, Delta-doped β-gallium oxide field-effect transistor, Appl. Phys. Express. 10 (2017) 051102. https://doi.org/10.7567/apex.10.051102. [13] J. Yang, F. Ren, R. Khanna, K. Bevlin, D. Geerpuram, L. -C. Tung, J. Lin, H. Jiang, J. Lee, E. Flitsiyan, L. Chernyak, S. J. Pearton, A. Kuramata, Annealing of dry etch damage in metallized and bare (-201) Ga2O3, J. Vac. Sci. Technol. B. 35 (2017) 051201. https://doi.org/10.1116/1.4986300. [14] S. K. Cheung, N. W. Cheung, Extraction of Schottky diode parameters from forward current‐voltage characteristics, Appl. Phys. Lett. 49 (1986) 85–87. https://doi.org/10.1063/1.97359. [15] K. Sasaki, M. Higashiwaki, A. Kuramata, T. Masui, S. Yamakoshi, Ga2O3 Schottky Barrier Diodes Fabricated by Using Single-Crystal β–Ga2O3 (010) Substrates, IEEE Electron Device Lett. 34 (2013) 493–495. https://doi.org/10.1109/led.2013.2244057. [16] X. Z. Liu, C. Yue, C. T. Xia, W. L. Zhang, Characterization of vertical Au/β-Ga2O3 single-crystal Schottky photodiodes with MBE-grown high-resistivity epitaxial layer, Chin. Phys. B. 25 (2016) 017201. https://doi.org/10.1088/1674-1056/25/1/017201. [17] K. Sasaki, M. Higashiwaki, A. Kuramata, T. Masui, S. Yamakoshi, MBE grown Ga2O3 and its power device applications, J. Cryst. Growth. 378 (2013) 591–595. https://doi.org/10.1016/j.jcrysgro.2013.02.015. [18] E. Farzana, Z. Zhang, P. K. Paul, A. R. Arehart, S. A. Ringel, Influence of metal choice on (010) β-Ga2O3 Schottky diode properties, Appl. Phys. Lett. 110 (2017) 202102. https://doi.org/10.1063/1.4983610. [19] L. A. M. Lyle, K. Jiang, E. V. Favela, K. Das, A. Popp, Z. Galazka, G. Wagner, L. M. Porter, Effect of metal contacts on (100) β-Ga2O3 Schottky barriers, J. Vac. Sci. Technol. A. 39 (2021) 033202. https://doi.org/10.1116/6.0000877. [20] B. Roul, T. N. Bhat, M. Kumar, M. K. Rajpalke, A. T. Kalghatgi, S. B. Krupanidhi, Analysis of the temperature-dependent current-voltage characteristics and the barrier-height inhomogeneities of Au/GaN Schottky diodes, Phys. Status Solidi A. 209 (2012) 1575–1578. https://doi.org/10.1002/pssa.201228237. [21] J. W. P. Hsu, Y. L. Loo, D. V. Lang, J. A. Rogers, Nature of electrical contacts in a metal–molecule–semiconductor system, J. Vac. Sci. Technol. B. 21 (2003) 1928. https://doi.org/10.1116/1.1588641. [22] T. Teraji, Y. Koide, T. Ito, High-temperature stability of Au/p-type diamond Schottky diode, Phys Status Solidi Rapid Res Lett. 3 (2009) 211–213. https://doi.org/10.1002/pssr.200903151.