Blue LED and Solid State Lighting

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1 Blue LED and Solid State Lighting Hyeonsik Cheong Department of Physics Sogang University

2 Nobel Prize in Physics 2014 Isamu Akasaki (1929) Hiroshi Amano (1960) Shuji Nakamura (1954) for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources 2

3 Isamu Akasaki Born in B.S. Kyoto Univ Research Associate, Assistant and Associate Professor, Nagoya Univ Dr. Eng., Nagoya Univ Matsushita Research Institute 1981 Professor, Nagoya Univ Professor Emeritus, Nagoya Univ. and Professor, Meijo Univ. 3

4 Hiroshi Amano Born in B.E. Nagoya Univ Dr. Eng. Nagoya, Univ Research Associate, Nagoya Univ Assistant, Associate, Professor, Meijo Univ Professor, Nagoya Univ. 4

5 Shuji Nakamura Born in , 1979, BE and ME, Tokushima Univ Nichia Corporation 1988 Visiting Scientist, Univ. of Florida 1994 Dr. Eng. Tokushima Unvi Professor, UC Santa Barbara 5

6 Blue LED 6

7 7

8 Full-color Display (RGB) 8

9 Is it worth a Nobel Prize?

10 History of Lighting 10

11 Electrical Lighting Incandescent lamp Edison s lamp: Carbon filament Tungsten filament Electricity Heat Light Arc lamp (HID) Electricity Gas Molecule Light Fluorescent lamp Electricity Mercury vapor UV light Visible light LED Electricity Light 11

12 Historical Development of Lighting 12

13 Comparison of Lamps Cost Comparison for 60 watt incandescent equivalent light bulb (U.S. residential electricity prices) Incandescent Halogen CFL LED (EcoSmart clear) LED (Philips) LED (Cree) Purchase price $0.41 $1.17 $0.99 $3.66 $1.50 $4.99 Watts lumens (mean) lumens/watt Lifespan (hours) 1,000 1,000 10,000 15,000 10,000 25,000 Energy cost over cents/kwh Total cost per 860 lumens over 20 years $289 $207 $67 $31 $41 $46 $307 $297 $78 $45 $52 $59 Comparison based on 6 hours use per day (43,800 hours over 20 yrs) 13

14 Energy Consumption 14

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16 LED Monitor: LCD Display + White LED Lamp 16

17 Fluorescent Lamp 17

18 LED Lamp (White LED) Blue LED + Yellow Phosphor UV LED + RGB Phosphor RGB LED 18

19 LED Lighting 19

20 LED Lighting for Major League Baseball 20

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22 History of Blue LED

23 History of LED (Light Emitting Diode) 1907, H. J. Round (Marconi Electronics) Observed light emission from SiC upon voltage 1927, Oleg Losev Systematic study of electrical light emission from SiC Phil. Mag. 6, 1024 (1928). 23

24 History of LED 24

25 Visible Spectrum Wavelength Energy 25

26 Light Emitting Diode (LED) 26

27 Principle of LED p type n type Electrons ( ) Band gap Hole(+) Photon Energy ~ Band Gap Energy 27

28 Elements for Semiconductors Band Gap C (diamond), Si, Ge GaAs, GaP, InP, GaN, AlN ZnO, ZnS, ZnSe, CdS, CdSe 28

29 Band Gap Energy of Semiconductors 29

30 First Blue LED 1979 Matsushita Electric 30

31 High Power Blue LED Motivation: Blue Laser Diode (LD) Structure of Laser Laser Diode 31

32 High Power Blue LED Motivation: Blue Laser Diode (LD) Why Blue Laser Diode? Optical Data Storage: CD, DVD, etc. 32

33 High Power Blue LED Motivation: Blue Laser Diode (LD) Why Blue Laser Diode? Optical Data Storage: CD, DVD, etc. Data capacity ~ 1/λ Diffraction Limit Numerical Aperture (N.A.) N. A. = n sin θ 33

34 High Power Blue LED Motivation: Blue Laser Diode (LD) Why Blue Laser Diode? Optical Data Storage: CD, DVD, etc. 34

35 High Power Blue LD 35

36 High Power Blue LED For High Efficiency Light Emission High quality semiconductor crystal Easy doping: both n and p types Limitations of GaN Difficult (almost impossible) to grow single crystals No appropriate substrates Difficult to obtain high quality materials Difficult to obtain p-type doping 36

37 Growth of High Quality GaN Metal Organic Vapor Phase Epitaxy (MOVPE, MOCVD) 37

38 Growth of High Quality GaN Low-Temperature Buffer Layer 38

39 P-type Doping 39

40 P-type Doping Mg doping followed by heat treatment 40

41 First High Brightness Blue LED 41

42 Blue Laser Diode! 42

43 Unfortunately, Laser diodes are not as important as expected 43

44 But, Solid state lighting exceeded everyone s expectation! 44

45 Shuji Nakamura Born in , 1979, BE and ME, Tokushima Univ Nichia Corporation 1988 Visiting Scientist, Univ. of Florida 1994 Dr. Eng. Tokushima Unvi Professor, UC Santa Barbara 2000 Becomes US citizen 2001 Files lawsuit for $180 million against Nichia (settles for $9 million) 45

46 Words from the winners Hold on to your dream. Don t be afraid to make mistakes experience is the best teacher. Isamu Akasaki I think the most important thing is students have to find out is what you like, what I like, you know. And almost it's like a dream. And then, just work hard for your dream. I think that's the best way, you know, to a good invention. Shuji Nakamura 46

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