Design of flexible ingan led separated from silicon substrate to optimizing the output light for vehicle head light (thiết kế đèn led ingan mềm được tách từ nền silicon để tối

https //iaeme com/Home/journal/IJPTM 17 editor@iaeme com International Journal of Production Technology and Management (IJPTM) Volume 13, Issue 1, January December, 2022, pp 17–20, Article ID IJPTM 13[.]

International Journal of Production Technology and Management (IJPTM)

Volume 13, Issue 1, January-December, 2022, pp 17–20, Article ID: IJPTM_13_01_003

Available online at https://iaeme.com/Home/issue/IJPTM?Volume=13&Issue=1

ISSN Print: 0976- 6383 and ISSN Online: 0976 – 6391

DOI: https://doi.org/10.17605/OSF.IO/8AVD3

© IAEME Publication

DESIGN OF FLEXIBLE INGAN LED

SEPARATED FROM SILICON SUBSTRATE TO OPTIMIZING THE OUTPUT LIGHT FOR

VEHICLE HEAD LIGHT

Danh Phan Hoang

Dong Nai Technology University, Vietnam

ABSTRACT

InGaN light emitting diode with a 1μ m-thick inserted sacrificial layer was grown and fabricated on the Si(111) substrate 5 μ m-thick InGaN light emitting membranes (GaN-LEM) has been demonstrated through an electrochemical lift-off (ECLO) process The lateral wet etching rate on the sacrificial layer was measured at 50μm/min for the separation process The optical properties of the InGaN membrane was analyzed through the photoluminescence spectra and the electroluminescence spectra Furthermore, the influence of stress on electroluminescence spectra was investigated

by bending up and down the membranes

Key words: GaN, Flexible substrates, Electrochemical Separation Process, Lift off,

Bending

Cite this Article: Danh Phan Hoang, Design of Flexible InGaN LED Separated from

Silicon Substrate to Optimizing the Output Light for Vehicle Head Light, International

Journal of Production Technology and Management (IJPTM), 13(1), 2022, pp 17–20

https://iaeme.com/Home/issue/IJPTM?Volume=13&Issue=1

1 INTRODUCTION

The current global technological market and society demands foldable, unbreakable and wearable technology, which can be exploited by a new generation of devices such as displays, photovoltaic optoelectronics, mobile phones, general lighting and in medical applications among others [1,2] Recently, OLEDs are seen as a way to achieve the above applications, especially flexible display However, OLEDs have some drawbacks, such as weak luminance, relatively low efficiency and lifetime, and a degradation on the device performances related to thermal degradation at high current densities, which limit their use for the production of high brightness displays and white lamps [3] On the other hand, inorganic light emitting diode (ILED) on sapphire substrate have some of the features better than OLEDs [4] Furthermore, the use of Si substrate offers many advantages such as low cost, good thermal conductivity, and the electronic functions In addition, there were many studies that separated LEDs from original substrates and transferred them to the other substrates in recent years, many applicable methods

Design of Flexible InGaN LED Separated from Silicon Substrate to Optimizing the Output Light for Vehicle

Head Light

including laser cutting [5], mechanical [6], inductively coupled plasma - reactive ion etching (ICP RIE) [7] exfoliations and few studies concentrated on using purely chemical solution [8] have been developed

In this paper, 5μm-thick GaN light emitting membrane (LEM) was fabricated through the electrochemical separation process and placed on the thermal release tape for measurement under bending conditions The optical and electrical properties of the bulk and GaN LEM were analyzed and discussed in detail

2 EXPERIMENTS

The InGaN LEDs used in this paper were grown on a 6-in Si(111) substrate In order to separate the LED from Si substrate, we deposited an AlN sacrificial layer between them Next, 150nm indium tin oxide (ITO) was deposited by an e-beam evaporator Subsequently, Cr/Al bilayers were deposited both on p-GaN and n-GaN were fabricated to act as the anode and cathode contacts, respectively

GaN LED chips with different scale 0.7×0.8cm2、2500×2500µm2 and 2500×1250µm2 in size were defined through a laser-scribing (LS) processes by using a 355nm laser that the LS channels were formed for the lateral wet etching process For electrochemical lift-off (ECLO), the etching solution was employed to etch the sacrificial layer between GaN buffer and Si substrate, which implements the lift off process for obtaining the GaN LEM After the lateral wet etching process, the GaN-LEM are separated from the bottom GaN/silicon substrates in the solution Fig 1(a) shows the GaN LED on Si substrate before ECLO Fig 1(b) shows the Si substrate after ECLO, and the line scribed by 355nm laser can be founded on the Si substrate Fig 1(c) shows different scale GaN LEM on thermal release tape and the size are marked Fig 1(d) shows GaN LEM on thermal release tape under bending condition, and the whole LEMs with bottom 4µm GaN epitaxial layer were bended for the following EL measurement

Figure 1 Photographs of (a) the GaN-LED on Si substrate, (b) Si substrate after ECLO, (c) different

scale GaN LEM on thermal release tape, (d) GaN LEM on thermal release tape under bending

condition

3 RESULT AND DISCUSSION

In Fig 2(a), the EL peak wavelength of the flat LEM structure (at 437.4nm) had a slightly red-shifted phenomenon compared with the non-separated LED/Si structure (437.1nm) at 2mA operation current Furthermore, the EL peak wavelength of LEM had red-shifted phenomenon from 437.4nm (flat) to 437.5nm (bend-down) and 437.9nm (bend-up) under the bending conditions The peak wavelength redshift phenomenon of the GaN-LEM was caused by the mechanical bending induced the compressive strain in the separated GaNLEM structure Fig 2(b) shows the photographs of these samples under the different bending conditions In Fig.2(c), the angle-resolved EL spectra of LEM and ST-LED were measured The divergent angles of the LEM structure (142o) was larger than the non-treated LED/Si structure (105o) These are

Danh Phan Hoang

because LEM has less light absorption by Si substrate after ECLO process and the light can be guided to the edge of LEM which shows in Fig 2(c)

(a)

(b)

(c)

Figure 2 (a) EL emission spectra at 2mA operation current and (c) Angle-resolved EL spectra of the

GaN-LED on Si substrate and LEM on thermal release tape (b) Photographs of LED on Si substrate and LEM on thermal release tape under different bending condition by injecting current

4 CONCLUSIONS

GaN light emitting membranes has been fabricated through the electrochemical separation process After the lifted-off process and transferred to thermal release tape, the EL emission spectra and angle-resolved EL spectra of the LED on the Si substrate and the InGaN-LEM

Design of Flexible InGaN LED Separated from Silicon Substrate to Optimizing the Output Light for Vehicle

Head Light

structure were measured Slightly blue-shifted of EL peak wavelength and broaden angle-resolved EL spectra were observed in the InGaN-LEM structure The freestanding InGaN-LEM structure has potential for the foldable optoelectronic devices applications

REFERENCES

[1] Choi, Won-Sik, Hyung Jo Park, Si-Hyun Park, and Tak Jeong "Flexible InGaN LEDs on a

polyimide substrate fabricated using a simple direct-transfer method." IEEE Photonics Technology Letters 26, no 21 (2014): 2115-2117

[2] Seo, Jung-Hun, Jing Li, Jaeseong Lee, Shaoqin Gong, Jingyu Lin, Hongxing Jiang, and

Zhenqiang Ma "A simplified method of making flexible blue LEDs on a plastic

substrate." IEEE Photonics Journal 7, no 2 (2015): 1-7

[3] Tian, Pengfei, Jonathan JD McKendry, Erdan Gu, Zhizhong Chen, Yongjian Sun, Guoyi Zhang,

Martin D Dawson, and Ran Liu "Fabrication, characterization and applications of flexible

vertical InGaN micro-light emitting diode arrays." Optics express 24, no 1 (2016): 699-707

[4] Zou, Xinbo, Xu Zhang, Wing Cheung Chong, Chak Wah Tang, and Kei May Lau "Vertical

LEDs on rigid and flexible substrates using GaN-on-Si epilayers and Au-free bonding." IEEE Transactions on Electron Devices 63, no 4 (2016): 1587-1593

[5] Li, Kwai Hei, Wai Yuen Fu, Y F Cheung, Kenneth Kin-Yip Wong, Y Wang, Kei May Lau,

and H W Choi "Monolithically integrated InGaN/GaN light-emitting diodes, photodetectors,

and waveguides on Si substrate." Optica 5, no 5 (2018): 564-569

[6] Tabares, Gema, Sarra Mhedhbi, Marie Lesecq, Benjamin Damilano, Julien Brault, Sebastien

Chenot, Abel Ebongue et al "Impact of the bending on the electroluminescence of flexible

InGaN/GaN light-emitting diodes." IEEE Photonics Technology Letters 28, no 15 (2016):

1661-1664

[7] Sha, Wei, Qilin Hua, Jiangwen Wang, Zifeng Cong, Xiao Cui, Keyu Ji, Xinhuan Dai, Bingjun

Wang, Wenbin Guo, and Weiguo Hu "Enhanced Photoluminescence of Flexible InGaN/GaN Multiple Quantum Wells on Fabric by Piezo-Phototronic Effect." ACS Applied Materials & Interfaces (2022)

[8] Chun, Jaeyi, Youngkyu Hwang, Yong-Seok Choi, Tak Jeong, Jong Hyeob Baek, Heung Cho

Ko, and Seong-Ju Park "Transfer of GaN LEDs from sapphire to flexible substrates by laser

lift-off and contact printing." IEEE Photonics Technology Letters 24, no 23 (2012): 2115-2118

[9] Horng, Ray-Hua, Ching-Ho Tien, Shih-Hao Chuang, Keng-Chen Liu, and Dong-Sing Wuu

"External stress effects on the optical and electrical properties of flexible InGaN-based green light-emitting diodes." Optics Express 23, no 24 (2015): 31334-31341

[10] Lin, Chia-Feng, Chun-Lung Su, Han-Ming Wu, Yi-Yun Chen, Bo-Song Huang, Kuan-Lin

Huang, Bing-Cheng Shieh, Heng-Jui Liu, and Jung Han "Bendable InGaN light-emitting

nanomembranes with tunable emission wavelength." ACS applied materials & interfaces 10,

no 43 (2018): 37725-37731