光
電
科
技
LED: Materials and Device Aspects
授課教師: 龔 志 榮 教授
國立中興大學物理學系
中華民國一○二年四月二十二日
1
§ 1-1 Optical Semiconductor Materials
*Elemental semiconductors： Si, Ge,（used in photodiodes only）
*Compound semiconductors
Ⅲ-Ⅴ compounds ＆ alloys
Ⅳ compounds ＆ alloys
Ⅰ-Ⅲ-Ⅵ2 compounds
Ⅱ-Ⅳ-Ⅴ2 compounds
Ⅳ-Ⅳ compounds
For applications in light emitting devices like LEDs and LDs as well as
photodiodes （solar cells ＆ photodetectors）
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*Bonding and Band structure in semiconductors
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Physical Properties of Optical Semiconductors
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cross-section of diffusion fabricated LED
light emitting in the pn junction
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EQE of LEDs in the visible spectrum
Table 1: III-V semiconductor LEDs’ wavelength, Color and Efficiency
LED material
Substrate
Type
Wavelength(nm)
Color
Efficiency
InGaN
Sapphire
D
370-680
UV-Red
Medium-High
AlGaInP
GaAs
D
560
Green
Medium
AlGaInP
GaP
D
570
Green
Medium
AlGaInP
GaP
D
590
Yellow
High
AlGaInP
GaP
D
607
Orange
High
AlGaInP
GaP
D
620-650
Red
High
AlGaAs
GaAs
D
650-675
Red
Medium
LED material
Substrate
Type
Wavelength(nm)
Color
Efficiency
GaAsP:N
GaP
I
589
Yellow
Low
GaAsP:N
GaP
I
632
Red
Low
GaAsP
GaAs
D
649
Red
Low
GaP
GaP
I
555
Green
Low
GaP:N
GaP
I
565
Green
Low
GaP:N,N
GaP
I
590
Yellow
Low
GaP:ZnO
GaP
I
699
Red
Medium
AlGaAs:Si
GaAs
D
820-890
IR
High
GaAs:Si
GaAs
D
920-950
IR
High
Cross-sectional schematic of a flip chip (覆晶) GaN LED
InGaAs LED containing a photonic crystal
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光
電
科
技
LED: Recent Advances and Applications
授課教師: 龔 志 榮 教授
國立中興大學物理學系
中華民國一○二年五月二十日
50
Internal Quantum Efficiency
Enhancement
52
Cheng-Liang Wang, Jyh-Rong Gong,* Ming-Fa Yeh, Bor-Jen Wu, Wei-Tsai Liao, Tai-Yuan Lin,
and Chung-Kwei Lin
* Department of Physics, National Chung Hsing University, TAIWAN, R.O.C.
IEEE Photonic Technology Letters 18 (2006) 1497
53
GaN-based LED structures w/wo SPSLs
Ni/Au
Ti/Al

p-GaN
MQWs
n-GaN (4mm)
Sample A



Undoped GaN
u-GaN ( 0.4mm)
Sample B
u-GaN ( 0.4mm)
Sample C


u-GaN + SPSL
5-pair
AlGaN(2nm)/
GaN(2nm)
SPSL
u-GaN ( 0.1mm)

sapphire substrate
u-GaN ( 0.4mm)

Sample D


u-GaN ( 0.1mm)
u-GaN ( 0.1mm)

u-GaN ( 0.4mm)

C. L. Wang et al. IEEE Photon. Tech. Lett. 18 (2006) 1497
C. L. Wang et al. IEEE Photon. Tech. Lett. 18 (2006) 1497
C. L. Wang et al. IEEE Photon. Tech. Lett. 18 (2006) 1497
p-GaN
InGaN/GaN
multi-quantum wells
n-GaN
n-GaN
100nm
2 sets of short period superlattices
u-GaN
C. L. Wang et al. IEEE Photon. Tech. Lett. 18 (2006) 1497
500nm
C. L. Wang et al. IEEE Photon. Tech. Lett. 18 (2006) 1497
Cheng-Liang Wang , Ming-Chang Tsai, Jyh-Rong Gong,* Wei-Tsai Liao, Ping-Yuan Lin, KuoYi Yen, Chia-Chi Chang, Hsin-Yueh Lin , and Shen-Kwang Hwang
* Department of Physics, National Chung Hsing University, TAIWAN, R.O.C.
Materials Science & Engineering B 138 (2007) 180
59
According to the standard Shockley model , the I–V relationship
of a forward-biased p–n junction can be approximated
by I = Is exp(q V/ηkT),
where Is, q, k, η and T, respectively, are saturation current of the
diode, electron charge, Boltzmann constant, and ideality factor
and absolute temperature of the diode.
60
Semilogarithmic I–V plots of the forward-biased In0.2Ga0.8N/GaNMQWLEDs having (a)
zero-set, (b) one-set, (c) two-set, and (d) three-set Al0.3Ga0.7N/GaN
SPSL insertion.
C. L. Wang et al. MSE B 138 (2007) 180
Typical optical surface morphologies of etched In0.2Ga0.8N/GaN
MQW LEDs having (a) zero-, (b) one-, (c) two-, and
(d) three-set Al0.3Ga0.7N/GaN SPSL insertion.
C. L. Wang et al. MSE B 138 (2007) 180
Typical I–V characteristics of the reverse-biased In0.2Ga0.8N/GaNMQW
LEDs (1) without SPSL insertion, (2) with one set of Al0.3Ga0.7N/GaN SPSL
insertion, (3) with two sets of Al0.3Ga0.7N/GaN SPSL insertion, and (4) with
three sets of Al0.3Ga0.7N/GaN SPSL insertion, respectively. The inset exhibits
plots of the corresponding EL intensity vs. emissionwavelength of the two LEDs
having no SPSL and two sets of SPSL operated at 20 mA.
C. L. Wang et al. MSE B 138 (2007) 180
C. L. Wang et al. MSE B 138 (2007) 180
Wei-Tsai Liao, Jyh-Rong Gong,* Cheng-Liang Wang, Wei-Lin Wang,
Chih-Chang Tsuei, Cheng-Yen Lee, Keh-Chang Chen, Jeng-Rong Ho, and
Ren C. Luo
* Department of Physics, National Chung Hsing University, TAIWAN, R.O.C.
Electrochemical and Solid-State Letters, 10 1 H5-H7 (2007)
65
Typical 0002 DCXRD curves of the In0.1Ga0.9N/Al0.03Ga0.97N
MQW LED structures grown on c- and a-plane sapphire substrates. Insets:
the corresponding XTEM micrographs of the LEDs near MQW area, respectively
W. T. Liao et al. Electrochem. Solid-State Lett. 10 (2007) H5
Characteristics of the In0.1Ga0.9N/Al0.03Ga0.97N MQW
LEDs grown on c- and a-plane sapphire substrates
W. T. Liao et al. Electrochem. Solid-State Lett. 10 (2007) H5
Plots of EL intensity vs forward current of the
In0.1Ga0.9N/Al0.03Ga0.97N MQW LEDs grown on c- and a-plane sapphire
substrates. Inset: a typical room-temperature EL spectra measured at 20 mA
for the In0.1Ga0.9N/Al0.03Ga0.97N MQW LEDs grown on c- and a-plane sapphire
substrates.
W. T. Liao et al. Electrochem. Solid-State Lett. 10 (2007) H5
Typical FESEM surface morphologies of the etched In0.1Ga0.9N/Al0.03Ga0.97N
MQW LEDs grown on a c- and b a-plane sapphire substrates
W. T. Liao et al. Electrochem. Solid-State Lett. 10 (2007) H5
External Quantum Efficiency
Enhancement
70
Kuo-Yi Yen, Chien-Hua Chiu, Chun-Wei Li, Chien-Hua Chou, Pei-Shin Lin, Tzu-Pei
Chen,Tai-Yuan Lin, and Jyh-Rong Gong*
* Department of Physics, National Chung Hsing University, TAIWAN, R.O.C.
IEEE PhotonicTechnologyLett.ers 24 (2012) 2105
71
72
Typical I-V curves of (a) N2-annealed n+-GZO contacts along with an
ITO contact on p-GaN/sapphire templates and (b) forward-biased InGaN/GaN
MQW LEDs with an as-deposited n+-GZO TCL, an ITO TCL and n+-GZO
TCLs being N2-annealed at 400 °C, 500 °C, 600 °C, 700 °C, and 800 °C.
K. Y. Yen et al. IEEE Photon.Tech.Lett. 24 (2012) 2105
Schematic showing electron tunneling in a
reverse-biased n+GZO/p-GaN hetero-junction
K. Y. Yen et al. IEEE Photon. Tech. Lett. 24 (2012) 2105
(a)–(f) θ-2θ XRD plots of asdeposited n+-GZO TCL and n+-GZO
TCLs on GaN/c-sapphire substrates
being annealed at 400 °C, 500 °C,
600 °C, 700 °C, and 800 °C for 5 min
in N2 ambient.
K. Y. Yen et al. IEEE Photon.Tech.Lett.
24 (2012) 2105
Light output powers of InGaN/GaN MQW LEDs with as-deposited
n+-GZO, 400 °C N2-annealed n+-GZO and commercial ITO TCLs
K. Y. Yen et al. IEEE Photon. Tech. Lett. 24 (2012) 2105
Optical transmittances of as-deposited n+-GZO, 400 °C N2-annealed
n+-GZO and ITO films deposited on c-sapphire substrates
K. Y. Yen et al. IEEE Photon. Tech. Lett. 24 (2012) 2105
78