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

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- compounds Ⅴ ＆ alloys Ⅳ compounds ＆ alloys Ⅰ- -Ⅲ Ⅵ2 compounds Ⅱ- -Ⅳ Ⅴ2 compounds Ⅳ- compoundsⅣ 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

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

Table 1: III-V semiconductor LEDs’ wavelength, Color and Efficiency

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

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Cheng-Liang Wang, Jyh-Rong Gong,* Ming-Fa Yeh, Bor-Jen Wu, Wei-Tsai Liao, Tai-Yuan Lin, and Chung-Kwei Lin

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IEEE Photonic Technology Letters 18 (2006) 1497

* Department of Physics, National Chung Hsing University, TAIWAN, R.O.C.

GaN-based LED structures w/wo SPSLs

Undoped GaNu-GaN + SPSL

p-GaN

5-pair AlGaN(2nm)/GaN(2nm) SPSL

Sample A

u-GaN ( 0.1mm)

MQWsSample B

Sample C

Sample D

u-GaN ( 0.1mm)u-GaN ( 0.1mm)

sapphire substrate

n-GaN (4mm)

Ni/Au

Ti/Al

u-GaN ( 0.4mm)

u-GaN ( 0.4mm)

u-GaN ( 0.4mm)

u-GaN ( 0.4mm)

C. L. Wang et al. IEEE Photon. Tech. Lett. 18 (2006) 1497



InGaN/GaNmulti-quantum wells

2 sets of short period superlattices

500nm

100nm

u-GaN

n-GaN

p-GaN

n-GaN



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Cheng-Liang Wang , Ming-Chang Tsai, Jyh-Rong Gong,* Wei-Tsai Liao, Ping-Yuan Lin, Kuo-Yi Yen, Chia-Chi Chang, Hsin-Yueh Lin , and Shen-Kwang Hwang


Materials Science & Engineering B 138 (2007) 180

According to the standard Shockley model , the I–V relationshipof 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 thediode, electron charge, Boltzmann constant, and ideality factorand absolute temperature of the diode.

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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/GaNSPSL 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

C. L. Wang et al. MSE B 138 (2007) 180

Typical I–V characteristics of the reverse-biased In0.2Ga0.8N/GaNMQWLEDs (1) without SPSL insertion, (2) with one set of Al0.3Ga0.7N/GaN SPSLinsertion, (3) with two sets of Al0.3Ga0.7N/GaN SPSL insertion, and (4) withthree sets of Al0.3Ga0.7N/GaN SPSL insertion, respectively. The inset exhibitsplots of the corresponding EL intensity vs. emissionwavelength of the two LEDshaving no SPSL and two sets of SPSL operated at 20 mA.

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, andRen C. Luo

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Electrochemical and Solid-State Letters, 10 1 H5-H7 (2007)


Typical 0002 DCXRD curves of the In0.1Ga0.9N/Al0.03Ga0.97NMQW 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


Plots of EL intensity vs forward current of theIn0.1Ga0.9N/Al0.03Ga0.97N MQW LEDs grown on c- and a-plane sapphiresubstrates. Inset: a typical room-temperature EL spectra measured at 20 mAfor the In0.1Ga0.9N/Al0.03Ga0.97N MQW LEDs grown on c- and a-plane sapphiresubstrates.


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


External Quantum Efficiency Enhancement

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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*

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IEEE PhotonicTechnologyLett.ers 24 (2012) 2105

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Typical I-V curves of (a) N2-annealed n+-GZO contacts along with anITO contact on p-GaN/sapphire templates and (b) forward-biased InGaN/GaNMQW LEDs with an as-deposited n+-GZO TCL, an ITO TCL and n+-GZOTCLs 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

K. Y. Yen et al. IEEE Photon.Tech.Lett. 24 (2012) 2105

(a)–(f) θ-2θ XRD plots of as-deposited 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.

Light output powers of InGaN/GaN MQW LEDs with as-depositedn+-GZO, 400 °C N2-annealed n+-GZO and commercial ITO TCLs


Optical transmittances of as-deposited n+-GZO, 400 °C N2-annealedn+-GZO and ITO films deposited on c-sapphire substrates


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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

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