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青色/緑色半導体レーザー技術の最前線

Technology Frontier of Blue and Green Semiconductor Lasers

Hiroaki OHTA and Shuji NAKAMURAMaterials department, University of California, Santa Barbara

Received September 5, 2010

Green laser diodes (LDs) have been realized using InGaN-based nitride semiconductors. Although the basic structure of green LDs is essentially same as that of violet LDs, it took around 15 years to establish the technology to grow high-quality active regions for green emission since the fi rst demonstration of nitride LDs. In this paper, we review present and future subjects of InGaN-based green LDs as well as technologies of matured red/blue LDs and topics of nonpolar/semipolar GaN materials.

Key Words: Green laser, Semiconductor laser, InGaN, Nonpolar and semipolar GaN, Display

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Fig. 1 Color range when using three 460/530/630 nm la-ser optical sources plotted on the CIE 1931 color space chromaticity diagram.

2010 10738

DVD

/ /

Fig. 1

1 nm 460 530

630 nm

2008

/ / 7.6/6.0/9.7 W

135 W

65 1

635.1 nm 7.2 W2 25 AlGaInP

300 mW

23 % 644 nm

7 W

UHP 5000

10000 3 AlInGaP

COD

GaN III

440-460 nm

405 nm

Fig. 2 (a) Maximum output power per single emitter un-der pulsed or cw operation as a function of wave-length. (b) wall-plug effi ciencies at the maximum output powers corresponding to (a). Note that var-ious active region widths are used. Diamond, tri-angle, and rectangle points correspond to InGaN LDs, SHG pumped by IR LDs, and AlGaInP LDs, respectively.

38 10 / 739

4

InGaN In

In 30 %

GaN

InGaN

GaN AlGaN 1000

In InGaN 800

c GaN

5

/6 445 nm

1.4 W 3 W

c GaN7 1 W

COD

1.2 W 24 % 1 A

1 W

30000

m 8 c

GaN

c

In

Fig. 2 c GaN

AlGaInP

αm/ αm α i η d

/

αm α i η d

9 7 W

644 nm = 1.9 eV 1.2 W

445 nm = 2.8 eV

2.35 V and 4.8 V 3,7

10 % 99 % αm = 23 cm 1 α i =

10 cm 1 η d 100 %

40-60 %

/

SHG

1060 nm

1,10 Corning

InGaAs 1060 nm

PPMgLN periodic-poled MgO-doped lithium nio-

bate 530 nm

10 Corning

15

10.8 W 304 mW

304 mW 72.9 % 10

15-20 % /

2009

GaN11 c GaN

c

LED DVD 4

400 nm

15 510 nm12 15 In

InGaN

GaN

c

5,6 In

Fig. 3 Top fi gure: Spontaneous emission and lasing spec-tra of 516 nm green LD developed by UCSB re-search group. Bottom fi gure: L-I and V-I curves of the same green LD.37

Fig. 4 The relative LED output powers for m m- and the (2021) plane according to the UCSB after Lin et al.37

2010 10740

GaN

c GaN

LED

GaN LED

510-515 nm 8 mW12

520-524 nm 50 mW 13,14

524 nm

50 mW

2.3 %

13

c

c 90

c

6

16 18 c

m GaN 19,20

m

500 nm 21 27 490-

500 nm

0.5-4 % c

24 In 520-

530-nm

28 m

UCSB

1122 29

32 30

33

2009 m 15 2021

531 nm 34,35

2.5 mW

0.22 % Fig. 3 UCSB

Al GaN

2021 516 nm36 38 Fig. 4 m 2021 LED

500 nm 202137

/ GaN

525 nm39 522 nm 30 mW

0.8 %

/ GaN

32,40

20,41 m

c40

Table 1 Summary of the typical device performance of InGaN-based green LDs. The parameters λ , Lmax, Ith, Jth, and Vth are the lasing wavelength, maximum output power, threshold current, threshold current density, and threshold voltage, re-spectively.

38 10 / 741

1122

1123 m

32 2021

101434

GaN8

GaN

2021

Fig. 2 /

LED

Table 1 2009

2010

c /

3

InGaN

3

9

gΓ αm α i

g Γ

I

s t Itr g I ≈ η i s I Itrt

Ith = { αm α i /sη iΓ}1/t Itr

η i

1 η i

η i Ith

αm α i ∝ η i αm α i = xη i

25,34

q

100 %

αm α i = xη i P ∝

xη i α i η d/η i

η d

42

η i 30 %

2009

40 %

100 % Fig. 2

LED

LED 30 %43 c LED

/

In 30 %

InGaN

Fig. 4

UCSB Al

2010 10742

37

SHG

LED 2

In

InGaN

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