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1 AlGaN/GaN Influence of metal material on capacitance for Schottky-gated AlGaN/GaN 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 1, 1 1

2 AlGaN/GaN デバイス ① GaNの優れた物性値 ② AlGaN/GaN HEMT構造ワイドバンドギャップ半導体 (3.4eV) 絶縁破壊電界が大きい (3 16 V/cm) 飽和電子速度が速い ( cm/s) Thermal Conductivity 5 High Tem. 4 Operation 3 Electric Field High Voltage Operation GaN 2 Si Energy Gap Electron Mobility SiC 1 Yole développement, Power GaN, 212 高い電子移動度 (2cm2/Vs) Schottky metal PSP 2DEG Ec PPE PSP Al.25Ga.75N EF GaN Melting Point Electron Velocity High Frequency Operation ヘテロ界面に2DEG形成高周波パワーデバイスへの利用に期待 2

3 ( Cu ) S G D Al.25 Ga.75 N GaN 2DEG Buffer layer Si (111)Substrate 3

4 AlGaN/GaN HEMT W Al S G Al.25 Ga.75 N D GaN 2DEG Buffer layer Si (111)Substrate,,W,Al 4

5 i-al.25 Ga.75 N(25nm)/i-GaN(1µm) on buffer/si(111) SPM and HF cleaning Oxide deposition (plasma-teos) Patterning and BHF for SiO 2 etching Mesa isolation (RIE with Cl 2 ) SPM and BHF for SiO 2 etching Oxide deposition (plasma-teos) Patterning and BHF for S/D contact opening Metal deposition (Sputtering) (5nm)/Al(6nm)/Ti(5nm) /Al /Ti Al.25 Ga.75 N (25nm) GaN(1µm) Buffer layer (1µm) Si(111) Substrate Al.25 Ga.75 N (25nm) GaN(1µm) Buffer layer (1µm) Si(111) Substrate TEOS-SiO 2 /Al /Ti 2DEG AlN (1nm) AlN (1nm) 5

6 Patterning and RIE with Cl 2 for S/D contact Annealing in N 2 at 95 o C for 3 sec Oxide deposition (plasma-teos) Patterning and BHF for gate opening SPM and HF cleaning Gate metal (,, W, Al) deposition (Sputtering) Gate patterning Contact opening (Buffered HF) Current [A] sec in N 2 (5nm) /Al(6nm) /Ti(5nm) -6x Voltage [V] /Al /Ti 8µm 3µm Metal 95 o C 5 o C /Al /Ti Al.25 Ga.75 N (25nm) 15µm TEOS-SiO 2 FGA (H 2 : N 2 = 3% : 97%) for 1min Measurement CV,IV,Gp/ω,Current collapse AlN (1nm) GaN(1µm) Buffer layer (1µm) Si(111) Substrate 2DEG 6

7 Capacitance [pf] L / W = 25 / 1µm FGA 3 o C for 1 min 1kHz 1kHz 5kHz 1MHz Capacitance [pf] Capacitance [pf] W Gate Voltage [V] Gate Voltage [V] Gate Voltage [V] (-4V) W 1kHz 7

8 Gate Leakage Current [A/cm 2 ] Al W L / W = 25 / 1µm FGA 3 o C for 1 min Gate Voltage [V] Drain Current [A] V ds = 1V V ds =.5V L / W = 25 / 1µm FGA 3 o C for 1 min Gate Voltage [V] 8

9 (x1-8 ).6 G p /ω (S sec/cm 2 ).4.2. Conductance spectra (G p /ω) V g = -6.V -4.4V -6.V V g = -4.4V Frequency (Hz) D it (cm -2 /ev) τ (sec) D it and time constant (τ) Gate voltage (V) (5% )D it ( ) 9

10 (x1-8 ) G p /ω (S sec/cm 2 ) Conductance spectra (G p /ω) gate gate -3.V -3.2V V g = -4.1V V g = -3.6V Frequency (Hz) D it (cm -2 /ev) τ (sec) D it and time constant (τ) Gate voltage (V) -3.1 D it 1

11 g m (S) W/L=1/25µm V d =.5V V g (V) g m g m (AlGaN/GaN ) 11

12 : (Hole-like traps) : AlGaN 12

13 2 2 2 Drain Current [ma] Drain Current [ma] V gs = 6V L / W = 25 / 1µm FGA 3 o C for 1 min Drain Voltage [V] V gs = 6V V ds = 1V W 4 Drain Current [ma] V gs = 6V L / W = 25 / 1µm FGA 3 o C for 1 min Drain Voltage [V] Drain Current [ma] W Reduced I d V gs = 6V L / W = 25 / 1µm FGA 3 o C for 1 min Drain Voltage [V] ( ),W Drain Bias [V] 13

14 , AlGaN AlGaN AlGaN/GaN (ON ) 14

15 12 1 Annealing for 1 min L / W = 25 / 1µm 12 1 Annealing for 1 min L / W = 25 / 1µm Capacitance [pf] o C 4 o C 5 o C 6 o C Capacitance [pf] o C 4 o C 5 o C 6 o C 2 at 1 khz (a) Gate Voltage [V] 2 at 1 khz (b) Gate Voltage [V]

16 Gate Leakage Current [A/cm 2 ] Open : at 1 V Solid : at -5 V Annealing Temperature [ o C] 8

17 g m, max [µs] Annealing for 1 min V ds =.5V Reduction in g m, max 4 No FET operation with above 5 o C Annealing Temperature [ o C] 8

2DEG at AlGaN/GaN interface Ambacher O. et al., JAP, 85, 3222, 1999. AlGaN P SP P PE Schottky metal P SP P PE 2DEG E c P SP E F GaN P SP Al.25 Ga.

18 2DEG at AlGaN/GaN interface Ambacher O. et al., JAP, 85, 3222, AlGaN P SP P PE Schottky metal P SP P PE 2DEG E c P SP E F GaN P SP Al.25 Ga.75 N GaN P SP : Spontaneous polarization P PE : Piezoelectric polarization 2DEG (~1 13 cm -2 ) are obtained without any doping. High electron mobility transistor (HEMT) is possible.

19 6 inch AlGaN/GaN substrate

20 I d -V d characteristics Drain Current [ma] L / W = 25 / 1µm FGA 3 o C for 1 min V gs = V -1V -2V Drain Current [ma] V gs = V -1V -2V Drain Current [ma] W V gs = V -1V -2V -3V -3V -3V Drain Voltage [V] Drain Voltage [V] Drain Voltage [V] 1 Fabrication and operation of HEMT with,, W Al-gated HEMT : large gate leakage current

21 Current collapse W. Saito (TOSHIBA), 21/6/24 G. Meneghesso et al., Microelectron. Eng, vol. 19, pp , 213. Low Drain Voltage High Drain Voltage Trap are thought to be related to frequency dispersion. Evaluation of current collapse

22 Current collapse vs. nitrogen Drain Current [ma] (a) (b) (c) V gs = 6V L / W = 25 / 1µm FGA 3 o C for 1 min Drain Current [ma] 15 1 V gs = 6V 5 L / W = 25 / 1µm FGA 3 o C for 1 min Drain Voltage [V] Drain Voltage [V] Drain Current [ma] 15 1 Reduced I d (N 2 :Ar=3:7) (N 2 :Ar=2:8) (N 2 :Ar=1:9) V gs = 6V 5 L / W = 25 / 1µm FGA 3 o C for 1 min 2 3 Drain Voltage [V] 4 Current collapse are found to be correlated to nitrogen. Higher nitrogen concentration can suppress the collapse.

23 Current collapse & C-V characteristics Drain Current [ma] V gs = 6V V ds = 15V (N 2 :Ar=3:7) (N 2 :Ar=2:8) (N 2 :Ar=1:9) Capacitance [pf] FGA 3 o C for 1 min L / W = 25 / 1µm N 2 :Ar = 1:9 N 2 :Ar = 2:8 N 2 :Ar = 3:7 at 1 MHz Drain Bias [V] Gate Voltage [V] Current collapse depend on the nitrogen concentration. Same capacitance indicates no unintended layer.

24 Gate leakage and I d -V g characteristics Gate Leakage Current [A/cm 2 ] N 2 :Ar = 1:9 N 2 :Ar = 2:8 N 2 :Ar = 3:7 L / W = 25 / 1µm FGA 3 o C for 1 min Gate Voltage [V] Drain Current [A] V ds =.5V N 2 :Ar = 1:9 N 2 :Ar = 2:8 N 2 :Ar = 3:7 L / W = 25 / 1µm FGA 3 o C for 1 min Gate Voltage [V] Higher nitrogen concentration provides lower leakage. These results coincide with the use of various metals.

25 Conclusions Gate metal induce effects has been experimentally investigated with the use of various metals Gate metal strongly affect on the current collapse, gate leakage current and frequency dispersion in C-V characteristics. can suppress the current collapse compared with conventional metal. trogen concentration in are found to be related to the current collapse and gate leakage current. The dependence of the current collapse on nitrogen concentration indicates that the nitrogen defects are origin responsible for the traps.

Conduction Mechanism at Low Temperature of 2-Dimensional Hole Gas at GaN/AlGaN Heterointerface （低温におけるGaN/AlGaN ヘテロ界面の2 次元正孔ガスの伝導機構）

Conduction Mechanism at Low Temperature of 2-Dimensional Hole Gas at GaN/AlGaN Heterointerface （低温におけるGaN/AlGaN ヘテロ界面の2 次元正孔ガスの伝導機構） 2014/03/19 応用物理学会 2014 年春季学術講演会コンダクタンス法による AlGaN/GaN ヘテロ接合界面トラップに関する研究 Investigation on interface traps in AlGaN/GaN heterojunction by conductance method 劉璞誠 1, 竇春萌 2, 角嶋邦之 2, 片岡好則 2, 西山彰 2, 杉井信之 2,