GaNGaNgroupgroup

Hokkaido University

1

第４回窒化物半導体応用研究会

橋詰Ჽ保Ჽ

北海道大学Ჽ量子集積ᶺ研究ḅ

GaNᵩᶧᶒAlGaNᶍ欠陥準位ᶇ表面準位

GaNGaNgroupgroup

Hokkaido University

2

1) AlGaNの深い準位の評価 2) AlGaNの表面準位の評価と制御3) 高温処理によるp-GaN表面の変成

Outline

光ᶶ

電子ᶶ

発光効率᳀Ჽ安定動作᳀Ჽ信頼性᳀Ჽ寿命

安定動作᳀Ჽ信頼性

GaNGaNgroupgroup

Hokkaido University

3

Meneghesso et al, ED, 2006

After 150-h off-state stress

Before stress

Onuma, Chichibu, JAP, 2004

AlGaN/GaN HEMTᶍ劣化ᶇAlGaN結晶ᶍPL/CL

深ᵣ準位ᶍ発光

HEMTᶍ劣化

中ᶊ欠陥準位ᶍ発生

GaNGaNgroupgroup

Hokkaido University

4

GaNᲾAlGaNᶍ深ᵣ準位ᶍ報告

Ec

Ev

0.1 ~0.9 eV（電子トラップ）

Ga空孔

Mgアクセプター

GaNᶍ深ᵣ準位ᶍ報告

AlGaNᶍ深ᵣ準位ᶍ報告 非常ᶊ少ᶉᵣ

検出ᵴᶫᶅᵣᶉᵣ領域

0.3 eV

GaNGaNgroupgroup

Hokkaido University

5

n-Al0.26Ga0.74Nᶊ対ᵸᶪDLTS評価

Ti/Al/Ti/Au

n-Al0.26Ga0.74N

Ni/Au

200µm

LT-GaNSi : 1x1017cm-3

sapphire 10-12

10-10

10-810-6

10-410-2

100102

-4 -3 -2 -1 0 1 2

電流密度

(A/c

m2 )

電圧 (V)

n = 1.24φB = 1.2eV

-4 -2 0 2 4

5

4

3

2

1

0

1/C2

(x 1

014 F

-2cm

2 )

電圧 (V)

φB = 1.3 eV

ダイオードの室温でのI-V、C-V特性

GaNGaNgroupgroup

Hokkaido University

6

DLTS測定結果

DLTS信号 アレニウスプロット

密度 5x 1016 cm-3

測定時間窓：10秒

100 200 300 400 500

DLTS

sig

nal

Temperature (K)

t1/ t2 = 1/10 s 0.1/1 s

104

105

106

2.5 2.6 2.7 2.8 2.9 3

ΔE= 1.0±0.2 eV

1000/ T (K-1)

T2 τ

(K2

s)

σn= 5x 10-13 cm2

GaNGaNgroupgroup

Hokkaido University

7

ᵲᶫᶝᶆᶍ報告ᶇᶍ比較

青ᵣ線᳃ParkᶨᲾAPL2005ᲽᲽᲽSi-dopedᲾ0-15ᲾMBE

黒ᵣ線᳃HogsedᶨᲾAPL2005ᲽᲽᲽSi-dopedᲾ14ᲾMBEᲽᲽᲽ1MeV電子線照射

赤ᵣ線᳃OsakaᶨᲾAPL2005ᲽᲽᲽᲽun-dopedᲾ9ᶇ17ᲾHVPE

我ᶍᲽᲽᲽᲽSi-dopedᲾ26ᲾMOVPE

101

102

103

104

105

106

0 2 4 6 8 101000/T (K-1)

τT2

(sK2

)Te

mpe

ratu

re-w

eigh

ted

time

cons

tant

AlxGa1-xN

~ 0.5eV

0.7~0.9eV

0.1~ 0.3eV

窒素空孔

~ 1.0eV

GaNGaNgroupgroup

Hokkaido University

8

0 200 4007000 7500 8000

Time (s)

Capa

citan

ce (p

F)1.0

0

VR= 0V

VR= -5V

dark

illumination (2.3 eV)

T= 360 K

Thermal emission of electrons from the 1.1-eV level

ΔCPH Optical emission of electrons from a level (1.1 < ΔE < 2.2 eV)

EFS

1.1 eV

1.1 eV

hv

deeper level

360 Kᶊᵩᵰᶪ容量過渡特性ᶇ光容量

near-midgaplevels

GaNGaNgroupgroup

Hokkaido University

9

EC

EV

0.1~0.9 eVᶍ電子 1.0 eV準位

(DLTS)

midgap準位(光容量

AlxGa1-xN (x< 0.3)ᶍ深ᵣ準位

禁制帯幅3.44.0 eV

GaNGaNgroupgroup

Hokkaido University

10

-10 -8 -6 -4 -2 0Voltage (V)

1

0

2

3

4

Capa

citan

ce (x

10-

7 F/c

m2 ) Ni/Al0.26GaN/GaN

300 Kf= 100 kHz

-5.2 -5.0 -4.8 -4.6 -4.4Voltage (V)

Capa

citan

ce (x

10-

7 F/c

m2 )

0

1

2

3

0Vから-8Vへ

-8Vで

10分保持

0Vへ連続sweep

-8Vから

2.3eV光照射

HEMT構造ᶍCV特性ᶊᵩᵰᶪ深ᵣ準位ᶍ影響

条件ᶍ違ᵣᶊᶧᶪCV曲線ᶍ᳃AlGaN中ᶍ深ᵣ準位ᶍ影響

面密度᳃ 5 x 1011~1 x 1012 cm-2

体積密度᳃Ჽ2~4Ჽx 1017 cm-3

GaNGaNgroupgroup

Hokkaido University

11

Characterization of “free” AlGaN surface

自由表面ᶍ電子準位ᶍ評価ᶎ難ᵶᵣ

電極ᶱ設置ᵸᶫᶏ自由表面ᶆᶎᶉᵮᶉᶪ

SPMᶣPLᵪᶨ得ᶨᶫᶪ情報᳃

ᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽᲽ間接的ᵪᶃᵣᵮᶃᵪᶍ仮定

GaNGaNgroupgroup

Hokkaido University

12

自由AlGaN 表面ᶍ電子準位᳅

laser beam

AlGaN(200-500 nm)air gap

ground plate

prism upper plate

reflection

measurement electrode

parallelism electrodes

Air-gap C-V characterization

Position control stepping motor piezo actuator

bottom view

GaNGaNgroupgroup

Hokkaido University

13

0

20

40

60

80

100

0 200 400 600 800 1000

Refre

ctivi

ty(%

)

Air-gap length (nm)

P-polarized light

The UHV gap was determined by measuring reflectivity that can be changed by penetration of evanescent wave.

laser: 780 nm0.8

0.9

1

-20 -10 0 10 20 30Voltage (V)

Norm

alize

d ca

pacit

ance

C/C

gap

expideal

Si/SiO2 reference

laser

air gap

air-gapᶍ測定ᶇ容量校正

GaNGaNgroupgroup

Hokkaido University

14

1010

1011

1012

1013

1014

-3.0 -2.0 -1.0 0.0

n-GaN

n-AlGaNC

upper electrode

air gap

Energy from EC (eV)

EC

Surfa

ce s

tate

den

sity

(cm

-2eV

-1)

midgap

n-Al0.27Ga0.73N layer by MOCVDhigh density !

1 μm

自由AlGaN 表面ᶍai-gapᲽCV評価

Gate voltage (V)

air gap: 320 nmideal

measured

Capa

citan

ce (p

F)

13.0

13.5

14.0

14.5

15.0

15.5

16.0

-100 -50 0 50 100

GaNGaNgroupgroup

Hokkaido University

15

Oxygen in AlGaN

n-GaNn-AlGaNInAlGaNp-AlGaN

SIMS analysis

Kyono et alJAP, 2006

High oxygen density1017 ~ 1018 cm-3 in AlGaN

GaNGaNgroupgroup

Hokkaido University

16

Al0.27GaN

GaN

Oxygen plasmaN2O plasma virgin

O2 plasma

Effects of oxygen introduction to AlGaN surface

0

5

10

15

20

25

30

0 2 4 6 8 10

I D (m

A)

VDS

(V)

Oxygen incorporation caused pronounced degradation of HEMT DC characteristics

ECR, 50W300 oC, 1min

GS D

virgin

N2O plasma

0

5

10

15

20

25

30

0 2 4 6 8 10

Dra

in C

urre

nt (m

A)

VDS

(V)

GaNGaNgroupgroup

Hokkaido University

17

Possible origins of surface electronic states

EC

EV

連続表面準位

density

離散準位

準位密度ᶎ表面状態ᶊᶧᶩ大ᵬᵮ異ᶉᶪ

1 x 1011Ჽ~ 1 x 1013 cm-2eV-1

型᳅

ᶴ型᳅

VN関連

酸素関連

GaNGaNgroupgroup

Hokkaido University

18

表面制御᳃SiN passivation

Surface control process

n-GaNsubstrate

n-AlGaN

SiN deposition by ECR-CVD

n-GaNsubstrate

n-AlGaNSiN

300 oC20 nm

1 μm

Energy from EC (eV)

EC

Surfa

ce s

tate

den

sity

(cm

-2eV

-1)

midgap

MOCVD n-Al0.27Ga0.73N

free surface

SiN-passivated

1010

1011

1012

1013

1014

-3.0 -2.0 -1.0 0.0

GaNGaNgroupgroup

Hokkaido University

19

表面制御᳃In-situ deposition of SiN

1000 oCSiH4 and NH3

mold

crystalline SiNX(wurtzite-like)

Pronounced reduction of surface potential

Increase in 2DEG density

Ogawa, Hashizume, JJAP 2007Takizawa et al, JEM, 2008

GaNGaNgroupgroup

Hokkaido University

20

10-13

10-11

10-9

10-7

10-5

10-3

10-1

Voltage (V)

Curre

nt (A

)

Ni/AlGaNSiN/AlGaN

SiN/Si0 5-5

Al0.3Ga0.7N 4.9 eV

4.1 eVSiNx

Fowler-Nordheim (FN) leakage

ΔEc= 0.6 ~ 0.7 eV

Small band offset at SiNx/AlGaN interface

SiNᶇAlGaN界面ᶍḅᶼ

points to note:• leakage in MIS gate structure• hot carrier injection in passivation structure

Leakage current characteristics

Hashizume, JVSTB, 2003

GaNGaNgroupgroup

Hokkaido University

21

-10 -5 0 5Voltage [V]

3

2

1

0

堆積直後

400℃Anneal

450℃Anneal

計算界面準位なし

Al2O3膜厚：26nm

原子層堆積ᶊᶧᶪAl2O3膜

2

0

4

6

8

10

5 10 150 20

E G (e

V)

Al0.3Ga0.7N

Si3N4

GaN

SiO2

AlN

dielectric constant, ε

Ga2O3

Al2O3

MgO

ZrO2HfO2

GaAsSi

種ᶍ絶縁膜ᶍEGᶇḥ

Al2O3膜ᵫAlGaNᶍ表面制御ᶊ有望

GaNGaNgroupgroup

Hokkaido University

22

高温処理ᶊᶧᶪp-GaN表面ᶍ変成

? 高温処理によるp-GaN表面の変成

ᶺḅḅḅGaN MOSFET作製

GaNGaNgroupgroup

Hokkaido University

23

試料ᶇ評価方法

XPS, SIMS

PL

GaNGaNgroupgroup

Hokkaido University

24

Mgp-GaN表面ᶍXPS評価᳃SiO2除去

141618202224

Inte

nist

y(a.

u.)

Binding Energy(eV)

1100oC

1000oC

reference

Ga3d

129013001310

Inte

nsity

(a.u

.)

Binding energy(eV)

1100℃

1000℃

reference

Ga2s

Mg1s半値幅ᶍ明ᶨᵪᶉ増加

GaNGaNgroupgroup

Hokkaido University

25

Mgp-GaN表面ᶍXPS評価᳃ᲽSiO2表面

050010001500

Inte

nsity

(a.u

.)

Binding energy(eV)

1000110012001300

O1s

Si

Ga2p 高温ᶴ中ᶍ反応模式図

GaNGaNgroupgroup

Hokkaido University

26

Mgp-GaN表面ᶍPL評価

2.2 2.4 2.6 2.8 3.0 3.2 3.4

p-GaN:Mg

PL In

tens

ity (a

.u.)

Photon energy(eV)

1100oC

1000oC

as-grown

×1

×1

×10

RT高温ᶴ

ᴣMgᶍ表面偏析ᴤGaᶍ外方拡散

表面近傍ᶊ欠陥生成

VGa + MgI

VGa + O

VN + MgI

Deep発光ᶍ増加

GaNGaNgroupgroup

Hokkaido University

27

1) AlGaN結晶ᵩᶧᶒAlGaN/GaN構造ᶊᶎmidgap近

傍ᶊ比較的高密度ᶍ深ᵣ準位ᵫ存在ᵸᶪ可能性ᵫᵡᶪᲿ

2) Air-gap CV法ᶎ自由表面ᶍ電子準位ᶱ評価ᵸᶪ上ᶆ有

用ᶉ手法ᶆᵡᶪᲿ

3) AlGaN表面ᶍ電子準位ᶱ制御ᵸᶪᵾᶠᶊᶎᲾ適切ᶉ表面制

御法ᶇ絶縁膜堆積法ᵫ必須ᶆᵡᶪᲿ

ᴦᲽp-GaNᶍ高温熱処理中ᶊGa外方拡散ᶇMgᶍ表面偏析ᶊ

起因ᵸᶪ深ᵣ準位ᶍ生成

Summary