Laser Lift-off Process

Experimentally determined decomposition depth caused by
a single pulse of a Nd:YAG laser in GaN at room
temperature as a function of the pulse intensity absorbed in
the thin GaN layer on sapphire.
The energy density of the laser shots
should be kept as close as possible
to the threshold value necessary for
GaN decomposition. Any additional
energy will lead to unwanted thermal
and mechanical stress which can
favour film spalling and peel-off after
sapphire removal.
The change in slope for pulse intensities exceeding 350 mJ/cm2 is probably
due to absorption or reflection of the laser light by the metallic Ga layer formed 63
during the process.
Dependence of the laser-induced etch depth of GaN
on the number of laser pulses with and without the
presence of HCl-vapor
The laser treatment was performed at 300 K with an absorbed pulse intensity of
290 mJ/cm2 and a pulse repetition rate of 10 Hz. From the slope of the straight
64
line an average etch rate of 330 nm/s can be deduced.
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