ISBN 9783843956321

978-3-8439-5632-1, Reihe Elektrotechnik

Nursidik Yulianto
GaN chip processing by femtosecond laser lift-off

173 Seiten, Dissertation Technische Universität Braunschweig (2025), Softcover, A5

Zusammenfassung / Abstract

Nowadays, gallium nitride (GaN) film delamination using laser lift-off (LLO) has become a crucial technique in GaN-based light-emitting diode (LED) technology. Conventionally, GaN decomposition via LLO is performed using various short-pulsed (nanosecond) lasers with wavelengths ranging from 193 to 355 nm, utilizing either excimer or Q-switched Nd:YAG lasers. Following the LLO process, GaN films can be transferred onto different substrates to enhance the light outcoupling efficiency of GaN-based LEDs and enable large-area electrical contacts on p-GaN layers.

Although the LLO technique is mature and widely adopted in the LED industry, numerous studies have explored alternative methods that offer greater benefits, versatility, and flexibility. These alternative approaches must be capable of detaching not only GaN-based LED films from their original sapphire substrates but also AlGaN-based devices. The main challenge lies in processing materials with wide band gaps, which are technically difficult to address using conventional LLO technology, especially when not equipped with a sacrificial layer. Therefore, more cost-effective and flexible systems are currently being investigated to reduce both the expense and complexity associated with traditional LLO setups—one of the technique’s key drawbacks.

To address the limitations of conventional LLO, femtosecond LLO (fs-LLO) has been introduced, employing nonlinear optical effects to induce III-nitride decomposition. This thesis focuses on developing a new potential LLO technique using an ultrashort-pulsed laser operating in the visible light regime, and on investigating the critical parameters influencing the process—such as laser scanning speed, laser energy per area, and chip size—during GaN and AlGaN films delamination and its subsequent transfer onto a copper foil substrate.