Ultrashort Pulse Laser Lift-Off Processing of InGaN/GaN Light-Emitting Diode Chips

authored by
Nursidik Yulianto, Grandprix T.M. Kadja, Steffen Bornemann, Soniya Gahlawat, Nurhalis Majid, Kuwat Triyana, Fatwa F. Abdi, Hutomo Suryo Wasisto, Andreas Waag

Gallium nitride (GaN) film delamination is an important process during the fabrication of GaN light-emitting diodes (LEDs) and laser diodes. Here, we utilize 520 nm femtosecond laser pulses, exploiting nonlinear absorption rather than single-photon absorption such as in conventional laser lift-off (LLO) employing excimer or Q-switched laser sources. The focus of this study is to investigate the influence of laser scanning speed and integrated fluence corresponding to laser energy per area during the LLO processing of GaN LED chips and their resulting structural properties. Because both the sapphire substrate and InGaN/GaN heterostructures are fully transparent to the emission of the laser system, a key question is related to the impact of laser pulses on the quality of a thin film structure. Therefore, several characterization methods (i.e., scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, and electroluminescence spectroscopy) were employed to understand the material modifications made by femtosecond LLO (fs-LLO). We demonstrated that by adjusting the laser scanning speed, smooth GaN surfaces and good crystal quality could be obtained regardless of the existing delamination of metal contact, which then slightly downgraded the LED performance. Here, the integrated fluence level was set in the range of 2.6-4.4 J/cm2 to enable the fs-LLO process. Moreover, two mitigation strategies were developed and proven to improve the optoelectrical characteristics of the lifted-off LEDs (i.e., modification of the processing step related to the metal creation and reduction of laser energy).

External Organisation(s)
Technische Universität Braunschweig
Lembaga Ilmu Pengetahuan Indonesia
Institut Teknologi Bandung (ITB)
Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)
Indian Institute of Technology Delhi (IITD)
Clausthal University of Technology
Gadjah Mada University
ACS Applied Electronic Materials
No. of pages
Publication date
Publication status
Peer reviewed
ASJC Scopus subject areas
Electronic, Optical and Magnetic Materials, Electrochemistry, Materials Chemistry
Electronic version(s)
https://doi.org/10.1021/acsaelm.0c00913 (Access: Closed)