Investigation of AlGaN/GaN Schottky barrier diodes on free-standing GaN substrate with low leakage current

Wu Peng; Zhang Tao; Zhang Jin-Cheng; Hao Yue

doi:10.7498/aps.71.20220161

Abstract

Benefiting from the excellent properties of GaN with a wide bandgap of 3.4 eV as well as high critical field of 3.3 MV/cm, GaN-based devices prove to be a promising candidate in extreme conditions. Especially, high-density high-mobility two-dimensional electron gas (2DEG) induced by spontaneous piezoelectric polarization in AlGaN/GaN heterostructure enables AlGaN/GaN device to lower on-resistance (R_ON). However, owing to the lack of free-standing GaN substrate with large size and high quality, the epitaxis of GaN is always based on hetero-substrate such as Al₂O₃, Si and SiC, which shows large lattice mismatch and thermal mismatch. The large mismatch between GaN and substrate leads to high dislocation as well as high leakage current (I_R) of GaN devices. In this work, high-performance AlGaN/GaN Schottky barrier diode with low I_R and low turn-on voltage (V_ON) is fabricated on a 3-inch free-standing GaN substrate with C-doping GaN buffer layer to suppress I_R. Owing to the suppressed dislocation density of the AlGaN/GaN epitaxial wafer on free-standing substrate, low Ohmic contact resistance (R_C) is difficult to achieve the suppressed penetration of Ohmic metal into 2DEG channel, which is adverse to the high current density. In this work, a low R_C of 0.37 Ω·mm is obtained by one-step self-aligned Ohmic process, including the etching of partial AlGaN barrier layer and lift-off of Ohmic metal. The 2DEG is formed under the effect of residual AlGaN barrier layer, and the short distance between 2DEG and Ohmic metal contributes to lowering the value of R_C. The groove anode region is defined by the low damaged inductively coupled plasma process with a low etching rate of 1 nm/min, and the total depth is 35 nm, confirmed by atomic force microscope. Fully removing the AlGaN barrier layer from the anode region makes the anode metal directly contact the 2DEG channel, thereby improving the performance of the fabricated AlGaN/GaN Schottky barrier diode (SBD) with a low V_ON of 0.67 V, low I_R of 3.6 × 10^–8 A/mm, and an I_ON/I_OFF ratio of up to 3 × 10⁷. The values of differential R_ON,sp are calculated to be 0.44, 0.86, 1.59, 2.55 mΩ·cm² for GaN SBDs with various values of L_AC of 6, 10, 15, 20 μm, and the values of R_ON,sp determined at an anode current density of 100 mA/mm are 1.27, 2.08, 3.29, 4.63 mΩ·cm², respectively. As the measured temperature increases from 300 to 425 K, the I_R is increased only by 3 times to 1.6 × 10^–7 A/mm, which shows the great potential for next-generation power electronics.

Keywords:

Authors and contacts

National Key Discipline Laboratory of Wide Bandgap Semiconductor, Xidian University, Xi’an 710071, China

Corresponding author: Zhang Tao, zhangtao@xidian.edu.cn ; Zhang Jin-Cheng, jchzhang@xidian.edu.cn ;

Funds: Project supported by the National Natural Science Foundation of China (Grant No. 62104185), the National Science Fund for Distinguished Young Scholars of China (Grant No. 61925404), and the Fundamental Research Fund for the Central Universities, China (Grant No. JB211103).

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References

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Cited By

图 1 自支撑衬底凹槽阳极结构AlGaN/GaN SBD器件截面图

Figure 1. Schematic cross-sectional of AlGaN/GaN SBD with groove anode on free-standing GaN substrate.

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图 2 器件凹槽阳极深度

Figure 2. Depth of the groove anode.

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图 3 测试电阻与传输线模型电极间距的线性拟合

Figure 3. Linear fitting of the measured resistance versus the TLM metal pad gap.

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图 4 自支撑氮化镓衬底凹槽阳极结构AlGaN/GaN SBD的正反向I-V曲线

Figure 4. Forward and reverse I-V curve of the fabricated AlGaN/GaN SBD with groove anode on free-standing GaN substrate.

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图 5 不同衬底结构AlGaN/GaN SBD开启电压与反向漏电的对应关系

Figure 5. Benchmarking the turn-on voltage and reverse current of AlGaN/GaN SBDs with various substrate.

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图 6 (a)线性坐标和(b)对数坐标下不同阴阳极间距AlGaN/GaN SBDs正向I-V特性

Figure 6. Forward I-V characteristics of the fabricated AlGaN/GaN SBDs with various L_AC in (a) linear-scale and (b) semi-log scale.

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图 7 半对数坐标下自支撑氮化镓衬底AGaN/GaN SBD正反向I-V特性随温度的变化关系

Figure 7. Temperature-dependent forward and reverse I-V characteristics of AlGaN/GaN SBD on free-standing GaN substrate in semi-log scale.

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图 8 AlGaN/GaN SBD理想因子及肖特基势垒高度随温度的变化关系

Figure 8. Extracted Schottky barrier height and ideality factor of AlGaN/GaN SBD as a function of the measured temperature.

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map

[1]	Zhang T, Wang Y, Zhang Y N, Lv Y G, Ning J, Zhang Y C, Zhou H, Duan X L, Zhang J C, Hao Y 2021 IEEE Trans. Electron Devices 68 2661 Google Scholar
[2]	Hao R H, Li W Y, Fu K, Yu G H, Song L, Yuan J, Li J S, Deng X G, Zhang X D, Zhou Q, Fan Y M, Shi W H, Cai Y, Zhang X P, Zhang B S 2017 IEEE Electron Device Lett. 38 1567 Google Scholar
[3]	Zhang L, Zheng Z Y, Yang S, Song W J, He J B, Chen K J 2021 IEEE Electron Device Lett. 42 22 Google Scholar
[4]	Zhang T, Li R H, Lu J, Zhang Y N, Lv Y G, Duan X L, Xu S R, Zhang J C, Hao Y 2021 IEEE Electron Device Lett. 42 1747 Google Scholar
[5]	Hsin Y M, Ke T Y, Lee G Y, Chyi J I, Chiu H C 2012 Phys. Status Solidi C 9 949 Google Scholar
[6]	Nela L, Erp R V, Kampitsis G, Yildirim H K, Ma J, Matioli E 2021 IEEE Trans. Power Electron. 36 1269 Google Scholar
[7]	Tsou C W, Wei K P, Lian Y W, Hsu S S H 2016 IEEE Electron Device Lett. 37 70 Google Scholar
[8]	Gao J N, Wang M J, Yin R Y, Liu S F, Wen C P, Wang J Y, Wu W G, Hao Y L, Jin Y F, Shen B 2017 IEEE Electron Device Lett. 38 1425 Google Scholar
[9]	Hu J, Stoffels S, Lenci S, Bakeroot B, Jaeger B D, Hove M V, Ronchi N, Venegas R, Liang H, Zhao M, Groeseneken G, Decoutere S 2016 IEEE Trans. Electron Devices 63 997 Google Scholar
[10]	Li X D, Hove M V, Zhao M, Geens K, Lempinen V P, Sormunen J, Groeseneken G, Decoutere S 2017 IEEE Electron Device Lett. 38 918 Google Scholar
[11]	Ma J, Matioli E 2018 Appl. Phys. Lett. 112 052101 Google Scholar
[12]	Zhang T, Lv Y G, Li R H, Zhang Y N, Zhang Y C, Li X D, Zhang J C, Hao Y 2021 IEEE Electron Device Lett. 42 477 Google Scholar
[13]	Zhou Q, Jin Y, Shi Y Y, Mou J Y, Bao X, Chen B W, Zhang B 2015 IEEE Electron Device Lett. 36 660 Google Scholar
[14]	Bahat-Treidel E, Hilt O, Zhytnytska R, Wentzel A, Meliani C, Wurfl J, Trankle G 2012 IEEE Electron Device Lett. 33 357 Google Scholar
[15]	Lee J G, Park B R, Cho C H, Seo K S, Cha H Y 2013 IEEE Electron Device Lett. 34 214 Google Scholar
[16]	Xiao M, Ma Y W, Cheng K, Liu K, Xie A, Beam E, Cao Y, Zhang Y H 2020 IEEE Electron Device Lett. 41 1177 Google Scholar
[17]	Wang T T, Wang X, He Y, Jia M, Ye Q, Xu Y, Zhang Y H, Li Y, Bai L H, Ma X H, Hao Y 2021 IEEE Trans. Electron Devices 68 2867 Google Scholar
[18]	Ma J, Santoruvo G, Tandon P, Matioli E 2016 IEEE Trans. Electron Devices 63 3614 Google Scholar
[19]	Gao J N, Jin Y F, Xie B, Wen C P, Hao Y L, Shen B, Wang M J 2018 IEEE Electron Device Lett. 39 859 Google Scholar
[20]	Zhang T, Zhang Y N, Zhang J C, Li X D, Lv Y G, Hao Y 2021 IEEE Electron Device Lett. 42 304 Google Scholar
[21]	Fu H Q, Fu K, Alugubelli S R, Cheng C Y, Huang X Q, Chen H, Yang T H, Yang C, Zhou J G, Montes J, Deng X G, Qi X, Goodnick S M, Ponce F A, Zhao Y J 2020 IEEE Electron Device Lett. 41 127 Google Scholar
[22]	Kizilyalli I C, Edwards A P, Nie H, Disney D, Bour D 2013 IEEE Trans. Electron Devices 60 3067 Google Scholar
[23]	Lin W, Wang M J, Yin R Y, Wei J, Wen C P, Xie B, Hao Y L, Shen B 2021 IEEE Electron Device Lett. 42 1124 Google Scholar
[24]	Liu X K, Gu H, Li K L, Guo L C, Zhu D L, Lu Y M, Wang J F, Kuo H C, Liu Z H, Liu W J, Chen L, Fang J P, Ang K W, Xu K, Ao J P 2017 AIP Adv. 7 095305 Google Scholar
[25]	Chu J Y, Wang Q, Jiang L J, Feng C, Li W, Liu H X, Xiao H L, Wang X L 2021 J. Electron Mater. 50 2630 Google Scholar
[26]	Alshahed M, Heuken L, Alomari M, Cora I, Toth L, Pecz B, Wachter C, Bergunde T, Burghartz J N 2018 IEEE Trans. Electron Devices 65 2939 Google Scholar
[27]	Gao J N, Jin Y F, Hao Y L, Xie B, Wen C P, Shen B, Wang M J 2018 IEEE Trans. Electron Devices 65 1728 Google Scholar
[28]	Wu J Y, Lei S Q, Cheng W C, Sokolovskij R, Wang Q, Xia G R, Yu H Y 2019 J. Vac. Sci. Technol. A 37 060401 Google Scholar
[29]	Zhang T, Zhang J C, Zhou H, Chen T S, Zhang K, Hu Z Z, Bian Z K, Dang K, Wang Y, Zhang L, Ning J, Ma P J, Hao Y 2018 IEEE Electron Device Lett. 39 1548 Google Scholar
[30]	Zhu M D, Song B, Qi M, Hu Z Y, Nomoto K, Yan X D, Cao Y, Johnson W, Kohn E, Jena D, Xing H G 2015 IEEE Electron Device Lett. 36 375 Google Scholar
[31]	Chen J B, Bian Z K, Liu Z H, Zhu D, Duan X L, Wu Y H, Jia Y Q, Ning J, Zhang J C, Hao Y 2021 J. Alloys Compd. 853 156978 Google Scholar
[32]	Toumi S, Ferhat-Hamida A, Boussouar L, Sellai A, Ouennoughi A, Ryssel H, 2009 Microelectron. Eng. 86 303 Google Scholar

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