GaN/metal/Si heterostructure fabricated by metal bonding and laser lift-off

Abstract

A process methodology has been adopted to transfer GaN thin films grown on sapphire substrates to Si substrates using metal bonding and laser lift-off techniques. After bonding, a single KrF (248 nm) excimer laser pulse was directed through the transparent sapphire substrates followed by low-temperature heat treatment to remove the substrates. The influence of bonding temperature and energy density of the excimer laser on the structure and optical properties of GaN films were investigated systemically. Atomic force microscopy, X-ray diffraction and photoluminescence measurements showed that (1) the quality of the GaN film was higher at a lower bonding temperature and lower energy density; (2) the threshold of the energy density of the excimer laser lift-off GaN was 300 mJ/cm2. The root-mean-square roughness of the transferred GaN surface was about 50 nm at a bonding temperature of 400 °C.

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

“…The calculated root-mean-square (rms) roughness ( S q ) values were lowered from 130.3 to 67.8 nm when the scanning speed was increased from v 1 = 1.5 m/s to v 3 = 2.5 m/s, respectively. These values are comparable with that of the GaN film surface released by the single KrF (248 nm) excimer nanosecond laser pulse (i.e., rms roughness of ∼50 nm) . That structure was successfully bonded onto silicon at a bonding temperature of 400 °C.…”

“…These values are comparable with that of the GaN film surface released by the single KrF (248 nm) excimer nanosecond laser pulse (i.e., rms roughness of ∼50 nm). 52 That structure was successfully bonded onto silicon at a bonding temperature of 400 °C. Another GaN layer processed by conventional LLO exhibited a similar rms value of (32 ± 5) nm, which was observed from the 400 μm 2 large AFM image.…”

Transferable Substrateless GaN LED Chips Produced by Femtosecond Laser Lift-Off for Flexible Sensor Applications

“…Therefore, it has been investigated by AFM and AES (Figure 4a-c). [5]. However, it should be noted that when the lifted chip needs to be transferred onto another foreign substrate, the produced roughness on its surface can still affect the bonding quality.…”

Low‐Energy UV Ultrafast Laser Controlled Lift‐Off for High‐Quality Flexible GaN‐Based Device

“…roughness of the separated GaN layer with this scheme was also unsatisfactory (≈68 nm) [ 25,26,28,29 ] and even inferior to that of the GaN surface separated by conventional approaches (≈50 nm). [ 30–32 ] It means the using of multi‐photons absorption in LLO was unfavorable for bonding prefabricated GaN‐based devices to foreign substrates or electrodes.…”