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首先测量了GaN肖特基二极管的正向变温电流-电压特性, 研究了其电流输运机制, 然后分析了在不同注入电流条件下的低频噪声行为. 结果表明: 1) 在正向高电压区, 热发射机制占主导, 有效势垒高度约为1.25 eV; 2) 在正向低偏压区(V < 0.8 V), 与位错相关的缺陷辅助隧穿电流占主导, 有效势垒高度约为0.92 eV (T = 300 K); 3) 在极小电流(I < 1 μA)和极低频率 (f < 10 Hz)下, 洛伦兹型噪声才会出现; 电子的渡越时间取决于多个缺陷对电子的不断捕获和释放过程, 典型时间常数约为30 ms (I = 1 μA); 4)在更高频率和电流下, 低频1/f噪声占主导; 电流的输运主要受到势垒高度的随机波动的影响, 所对应的系数约为1.1.
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关键词:
- GaN基肖特基二极管 /
- 输运机制 /
- 低频噪声
In this work, we first measure the forward temperature-dependent current-voltage (T-I-V) characteristics of the GaN-based Schottky diodes grown on the bulk GaN substrates, and then study the transport mechanisms of the forward current and the low-frequency current noise behaviors under various injection levels. The results are obtained below. 1) In a forward high-bias region the thermionic emission current dominates, and the extracted barrier height is about 1.25 eV at T = 300 K, which is close to the value measured by capacitance-voltage sweeping. 2) In a forward low-bias region (V < 0.8 V) the current is governed by the trap assist tunneling process, having an ideality factor much larger than 1, and the derived barrier height is about 0.92 eV at T = 300 K, which indicates that the conductive dislocation should be mainly responsible for the excessive leakage current, having a reduced barrier around the core of dislocations. 3) The Lorentzian noise appears only at very small current (I < 1 μA) and low frequency (f < 10 Hz), whose typical time constant is extracted to be about 30 ms, depending on the multiple capture and release process of electrons via defects. 4) At a higher frequency and current, the low-frequency 1/f noise becomes important and the corresponding coefficient is determined to be about 1.1, where the transport is affected by the random fluctuation of the Schottky barrier height.-
Keywords:
- GaN Schottky diode /
- transport mechanism /
- low-frequency noise
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图 1 Ni/Au/n-GaN肖特基二极管的横截面结构示意图(a)和器件俯视图(b)
Fig. 1. (a) Schematic cross-section diagram of the fabricated Ni/Au/n-GaN Schottky diode; (b) top view image of the devices.
图 2 Ni/Au/n-GaN肖特基二极管的掺杂浓度与结深关系曲线, 内插图为高频
$ 1/C^2 $ -V数据图Fig. 2. Dopant concentration as a function of junction depth of the fabricated Ni/Au/n-GaN Schottky diode. The inset shows a plot of
$ 1/C^2 $ vs. V.
图 3 正向偏压下的三种输运机制: 1, TE; 2, TFE; 3, FE, 实点代表GaN中的自由电子
Fig. 3. Three basic transport processes under forward bias: 1 is thermionic emission, 2 is thermal field emission, 3 is field emission. The solid dots represent electrons in GaN, and the solid ponts are free electron in GaN.
图 4 Ni/Au-GaN肖特基二极管的典型变温I-V特性曲线, 红色实线为300 K下TE模型
Fig. 4. Forward bias I-V characteristics of Ni/Au/n-GaN Schottky diode measured at different temperatures. The red solid line is the fitting line based on TE model at 300 K.
图 6 (a) n, (b) E0, (c)
$N_{\rm{D}}^* $ , (d) qφBn与温度的依赖关系Fig. 6. Derived values of (a) n, (b) E0, (c)
$N_{\rm{D}}^* $ , and (d) qφBn as a function of temperature.
图 7 GaN可导位错的能带结构示意图
Fig. 7. Schematic band gap diagram of the conductive dislocations in GaN.
图 8 I = 1 nA到100 µA的低频噪声谱
Fig. 8. Low frequency noise spectrum under I = 1 nA to 100 µA.
表 1 不同正向电流下的参数变化
Table 1. Values of different parameters at various forward currents.
I/nA A/10–8 B/10–9 τ/ms Aτ/10–7 r 1 4.36 4.96 50 2.18 1.09 10 8.09 7.79 45 3.64 1.13 100 8.25 7.20 40 3.30 1.10 1000 11.00 6.79 30 3.30 1.10 10000 6.12 1.10 100000 8.20 1.12 
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[1] Kotani J, Yamada A, Ishiguro T, Tomabechi S, Nakamura N 2016 Appl. Phys. Lett. 108 4
Google Scholar
[2] Sheu J K, Lee M L, Lai W 2005 Appl. Phys. Lett. 86 052103
Google Scholar
[3] Hsu J W P, Manfra M J, Lang D V, Richter S, Chu S N G, Sergent A M, Kleiman R N, Pfeiffer L N, Molnar R J 2001 Appl. Phys. Lett. 78 1685
Google Scholar
[4] Kaun S W, Wong M H, Dasgupta S, Choi S, Chung R, Mishra U K, Speck J S 2011 Appl. Phys. Express 4 3
Google Scholar
[5] Cao X A, Stokes E B, Sandvik P M, Leboeuf S F, Kretchmer J, Walker D 2002 IEEE Electron. Dev. Lett. 23 535
Google Scholar
[6] Hashizume T, Kotani J, Hasegawa H 2004 Appl. Phys. Lett. 84 4884
Google Scholar
[7] Lei Y, Lu H, Cao D, Chen D, Zhang R, Zheng Y 2013 Solid State Electron 82 63
Google Scholar
[8] Ren J, Yan D W, Yang G F, Wang F X, Xiao S Q, Gu X F 2015 J. Appl. Phys. 117 5
Google Scholar
[9] Zhang H, Miller E J, Yu E T 2006 J. Appl. Phys. 99 247
Google Scholar
[10] Madenach A J, Werner J H 1988 Phys. Rev. B 38 13150
Google Scholar
[11] Yan D W, Lu H, Chen D J, Zhang R, Zheng Y D 2010 Appl. Phys. Lett. 96 3
Google Scholar
[12] Yan D W, Jiao J P, Ren J, Yang G F, Gu X F 2013 J. Appl. Phys. 114 5
Google Scholar
[13] 王翔, 陈雷雷, 曹艳荣, 羊群思, 朱培敏, 杨国锋, 王福学, 闫大为, 顾晓峰 2018 物理学报 67 177202
Google Scholar
Wang X, Chen L L, Cao Y R, Yang Q S, Zhu P M, Yang G F, Wang F X, Yan D W, Gu X F 2018 Acta Phys. Sin. 67 177202
Google Scholar
[14] Chen L, Jin N, Yan D, Cao Y, Zhao L, Liang H, Liu B, Zhang E X, Gu X, Schrimpf R D, Fleetwood D M, Lu H 2020 IEEE Trans. Electron Devices 67 841
Google Scholar
[15] Cherns D, Jiao C G 2001 Phys. Rev. Lett. 87 4
Google Scholar
[16] Hawkridge M E, Cherns D 2005 Appl. Phys. Lett. 87 3
Google Scholar
[17] Elsner J, Jones R, Heggie M I, Sitch P K, Haugk M, Frauenheim T, Oberg S, Briddon P R 1998 Phys. Rev. B 58 12571
Google Scholar
[18] Lei H, Leipner H S, Schreiber J, Weyher J L, Wosinski T, Grzegory I 2002 J. Appl. Phys. 92 6666
Google Scholar
[19] Kumar A, Asokan K, Kumar V, Singh R 2012 J. Appl. Phys. 112 024507
Google Scholar
[20] Kumar A, Kumar V, Singh R 2016 J. Appl. Phys. 49 1
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